Zero Valent Iron

The arsenic content in wastewater is of major concern in copper mineral processing. Typically, a complex wastewater treatment is needed with a combination of chemical and physical processes. Electrocoagulation (EC) has shown its potential for arsenic removal due to the formation of ferric hydroxide-arsenate precipitates but the acidic conditions in the wastewater disfavours the hydroxide formation. This work evaluates the feasibility of EC combined with addition of zero valent iron nanoparticles in the treatment process. The results showed that copper smelter wastewater could be treated efficiently with EC and presence of nanoparticles. The treatment with EC or nanoparticles alone was less efficient. Increasing the concentration of nanoparticles during EC did not increase the efficiency accordingly. The arsenic removal was favoured by an increase of the current density during EC but only until a limiting current density; thereafter the anodes got partly passivated.

The reaction of selenate (Se(VI)) with zerovalent iron nanoparticles (nano Fe 0 ) was studied using both conventional batch equilibrium and X-ray spectroscopic techniques. Nano Fe 0 has a high uptake capacity for removal of dissolved Se(VI) reaching concentrations as high as 0.10 Se:Fe molar ratio in the solid product mixture. Kinetic studies of the Se(VI) uptake reaction in batch experiments showed an initial reaction rate (0-30 min) of 0.0364 min -1 which was four times greater than conventional Fe 0 powder. Analysis of the oxidation state of Se in the solid products by X-ray absorption near edge structure (XANES) spectroscopy showed evidence for the reduction of Se(VI) to insoluble selenide (Se(-II)) species. Structural analysis of the product by extended X-ray absorption fine structure (EXAFS) spectroscopy suggested that Se(-II) was associated with nano Fe 0 oxidation products as a poorly ordered iron selenide (FeSe) compound. The fitted first shell Se-Fe interatomic distance of 2.402 (±0.004) A matched closely with previous studies of the products of Se(IV)-treated Fe(II)-clays and zero-valent iron/ iron carbide (Fe/Fe 3 C). The poorly ordered FeSe product was associated with Fe 0 corrosion product phases such as crystalline magnetite (Fe 3 O 4 ) and Fe(III) oxyhydroxide. The results of this investigation suggest that nano Fe 0 is a strong reducing agent capable of efficient reduction of soluble Se oxyanions to insoluble Se(-II).

Bentonite clay supported nanoscale zerovalent iron (BC-nZVI) composite was successfully prepared. BC-nZVI was characterized by physicochemical and spectroscopic techniques. Surface area as determined by sear’s method is 291.2 cm2. Adsorption operational parameters were investigated in a batch technique. At 500 mg/L initial concentration, 120 minutes contact time and pH 3, 454.81 mg/g quantity was adsorbed. The highest adsorption percentage removal efficiency was obtained at room temperature. Kinetic data fitted best to pseudo second order and the mechanism was diffusion governed. The kinetic models were further validated by sum of square error (SSE) and non-linear Chi-square statistical models (X2). The values of the thermodynamic parameters: standard enthalpy change ΔH (-10.597 Jmol−1)to (-5558 Jmol−1.), standard entropy change, ΔS (-277.804 J mol−1 K−1)- to (-139.2595 J mol−1K−1) and the Gibbs free energy (ΔG) revealed that the adsorption process was feasible, spontaneous and exot...

There is escalating salinity levels on small islands due to uncontrolled groundwater extraction. Conventionally, this challenge is addressed by adopting optimal groundwater pumping strategies. Currently, on Unguja Island (Zanzibar), urban freshwater is supplied by desalination, which is expensive and energy-intensive. Hence, desalinization cannot be afforded by rural communities. This study demonstrates that the innovative Kilimanjaro Concept (KC), based on rainwater harvesting (RWH) can remediate seawater intrusion in Unguja, while enabling a universal safe drinking water supply. The reasoning is rooted in the water balance of the whole island. It is shown that if rainwater is systematically harvested, quantitatively stored, and partly infiltrated, seawater intrusion will be reversed, and a universal safe drinking water supply will be secured. Water treatment with affordable technologies (e.g., filtration and adsorption) is suggested. The universality of KC and its suitability for ...

In this paper, the treatability of white liquor by conventional (CFP), modified (MFP) and electro-Fenton oxidation processes (EFP) was investigated depending on the COD parameter. Based on the experimental results, up to 62.4%, 58.4% and 54.9% COD removals by the CFP, MFP and EFP were achieved, respectively. It was observed that adjustment of initial pH to acidic values is not required in the CFP. The optimal operational conditions were found to be

The removal of chemical oxygen demand (COD) and phenol from olive oil mill wastewaters (OOMW) was investigated experimentally by using conventional Fenton (CFP) and Fenton type processes (FTP) with zero valent iron (ZVI). Different operational parameters such as initial pH, Fe2+, Fe0, and H2O2 concentrations were examined. Kinetic studies in terms of COD and phenol removals for both CFP and FTP were performed. The original pH value (4.6) of OOMW for CFP was found as the optimum pH. The determined optimum conditions are [Fe2+] = 1500 mg L−1, [H2O2] = 1750 mg L−1, and pH = 4.6 for CFP; [Fe0] = 2000 mg L−1, [H2O2] = 2000 mg L−1, and pH = 3 for FTP. 82.4% COD and 62% phenol removals were performed under the optimum conditions by CFP, while 82% COD and 63.4% phenol were removed by FTP. According to the results of kinetic studies, it was observed that COD and phenol were removed by FTP more rapidly, compared to CFP. Consequently, it was determined that both CFP and FTP were effective proc...

Nanosized zero-valent iron (nZVI) is increasingly gaining interest as an efficient sorbent for various types of aqueous pollutants. In this study, nZVI was synthesised by the borohydride reduction method, characterised and then examined for the removal of aqueous Co 2+ ions over a wide range of concentrations, from 1 to 1000 mg/L. The size of nZVI particles was predominantly within the range of 20-80 nm, and only limited oxidation was observed in samples aged for a period of 2 months. The experiments investigated the effects of V/m ratio, concentration, contact time, repetitive loading, pH and aging on the extent of retardation of Co 2+ ions. Iron nanoparticles demonstrated very rapid uptake and large capacity for the removal of Co 2+ ions. Effective uptake was observed even after a number of repetitive trials. The extent of Co 2+ uptake increased with the increasing pH. X-ray photoelectron spectroscopy (XPS) indicate that the fixation of Co 2+ ions takes place through the interaction of these ions with the oxohydroxyl groups on the iron nanoparticle surfaces in addition to spontaneous precipitate formation at high loadings.

s of the Workshop of November 17-18, 1999 at Bitterfeld / Germany Holger Weiß 1, Huub Rijnaarts 2, Sjef Staps 2, Peter Merkel 3 (Editors) 1 Centre for Environmental Research LeipzigHalle, Interdisciplinary Department of Industrial and Mining Landscapes 2 Netherlands Organization for Applied Scientific Research, TNO Institute of Environmental Sciences, Energy Research and Process Innovation 3 Eberhard-Karls-University of Tübingen, Geological Institute, Applied Geology Group Abstracts Workshop SAFIRA projects Workshop SAFIRA project Editor’s Note: The opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the editors. Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Abstracts Workshop SAFIRA projects Workshop SAFIRA project

The application of advanced oxidation technologies (AOT) to a real and complex system was analyzed. The degradation of a real textile effluent in the presence of commercial steel wool (CSW, zero-valent iron) and H 2 O 2 as oxidant was studied. The effects of H 2 O 2 concentration (0-0.08 mol L -1 ), mass of CSW (0-0.4 g L -1 ) and temperature (15-45 °C) on the reduction of the chemical oxygen demand (COD) of the textile effluent were evaluated. Kinetic studies were performed at laboratory and pilot scales at different temperatures under optimal conditions (0.037 mol L -1 of H 2 O 2 and 0.247 g L -1 of CSW). Iron species (Fe 2+ , Fe 3+ , total Fe) were quantified in solution for different experiments as a function of time. COD reductions of 87.69% at lab scale and 89.55% at optimized pilot scale in 300 min (140.66 mgO 2 L -1 of COD, final discharge) were obtained. A metallurgical residue was tested as iron source, obtaining high COD removal (65%). Operating costs were calculated. Phytotoxicity tests performed before and after treatment showed that the effluent treated under optimal conditions was non-toxic. AOTs are based on physicochemical processes capable of producing

In this paper, a batch experiment was conducted to evaluate the water quality obtained from using pervious concrete (PERVC) technology to treat acid mine drainage (AMD). The study proposes an innovative application of PERVC as a permeable reactive barrier liner in evaporation ponds. The effectiveness of PERVC adsorbent in removing heavy metals was compared with that of zero-valent iron (ZVI) of particles sizes 1.0 to 1.8 mm. The AMD used in the study was obtained from abandoned gold and coal mines. PERVC mixtures consisted of granite aggregate and ordinary portland cement CEM I 52.5R (CEM I) or CEM I containing Class F 30% fly ash (30%FA) as a cement replacement material. ZVI was prepared from a mixture of silica sand and iron grit of specific sizes. PERVC and ZVI media were used to conduct batch reactor tests with AMD, for a period of 43 days at a ratio of one litre of reactive material to three litres of AMD. The quality of treated AMD was compared against effluent discharge standards. The contaminants Al, Fe and Zn were effectively removed by both PERVC and ZVI. Also, both adsorbents reduced Ni, Co and Cu to levels below those measured in raw AMD. However, PERVC was more effective in removing Mn and Mg while ZVI was ineffective. Although PERVC removed more heavy metals and with greater efficiency than ZVI, the PERVCtreated water showed high pH levels and exhibited elevated Cr 6+ concentrations, owing to leaching from the cement and fly ash materials used in PERVC mixtures.

In this paper, a batch experiment was conducted to evaluate the water quality obtained from using pervious concrete (PERVC) technology to treat acid mine drainage (AMD). The study proposes an innovative application of PERVC as a permeable reactive barrier liner in evaporation ponds. The effectiveness of PERVC adsorbent in removing heavy metals was compared with that of zero-valent iron (ZVI) of particle size 1.0 to 1.8 mm. The AMD used in the study was obtained from abandoned gold and coal mines. PERVC mixtures consisted of granite aggregate and ordinary Portland cement CEM I 52.5R (CEM I) or CEM I containing Class F 30% fly ash (30%FA) as a cement replacement material. ZVI was prepared from a mixture of silica sand and iron grit of specific sizes. PERVC and ZVI media were used to conduct batch reactor tests with AMD, for a period of 43 days at a ratio of 1 L of reactive material to 3 L of AMD. The quality of treated AMD was compared against effluent discharge standards. The contami...

Treatment of Pentachlorophenol (PCP) is challenging due to its hydrophobic nature and the stability of the carbon-chlorine bond, particularly in aromatic molecules. Zero Valent Iron (ZVI) has been used as an effective in situ passive treatment process for PCP contaminated groundwater. However, ZVI applications can experience a decrease in degradation rates over time due to: ZVI surface passivation, the formation of non-conducting iron oxides on the ZVI surface, and the accumulation of less chlorinated intermediates. In this study, ZVI modification by acid washing and formation of bimetallic systems by the incorporation of Nickel (Ni) was explored to overcome these limitations. PCP degradation was investigated in batch tests using ZVI as received (unwashed or UW) and acid washed (AW) ZVI. Two forms of bimetals were tested -one in which the Ni powder and ZVI (UW or AW) were physically mixed (Ni S /Fe) and the other in which the Ni was coated onto acid washed ZVI (Ni C /Fe) by reacting ZVI with NiSO 4 solutions. PCP dechlorination was confirmed by gas chromatography quantifying PCP and all intermediates formed. Raman spectroscopy was used to characterise the ZVI surfaces.

The present work aims at characterization of natural zeolites and their adsorption properties in respect to Pb+2, Cd+2, Fe+2 and Mn+2 ions inaqueous solutions. The zeolitized tuff samples provided from the Bulgarian deposits Belia Bair (BB) and Beli Plast (BP) and from Northern Chile (NCl), were studied in respect to chemical and mineralogical composition, as well as adsorption and ion exchange properties. The average content of clinoptilolite for both Bulgarian samples was found to be more than 75% and they had ion exchange capacity (NH4 +) varying from 107 to 121 meq/100g, respectively. Thermo-chemical modification of natural clinoptilolite from BB and BP was made in order to increase the ion exchange capacity up to 180 meq/100g. The results showed almost complete removal (>90 %) of all the metal ions studied. Activations of NCl-zeolite (118 m2 g-1) by pre-treatment with various ions greatly enhanced the Mn adsorption and mechanisms involved were elucidated. The maximum adsorpt...

Nitrate removal by laboratory and field continuous-flow zero-valent iron (Fe(0)) packed bed columns was evaluated for different influent water qualities (pH, dissolved oxygen (DO), nitrate concentration) and several months of operation (600-1500 bed volumes (BVs)). In contrast to previous batch experiments with Fe(0) where nitrate was stoichiometrically converted to ammonium, only 70% of the applied nitrogen was recovered as nitrate, ammonium, or nitrite (<0.1mg/L) during shorter-term column tests (2-20 BVs) and less than 25% of the applied nitrogen was recovered during longer-term field testing (500-1000 BVs) at elevated nitrate levels (approximately 25mg N/L). Nitrate removal was accompanied by a pH increase, DO decrease, and soluble iron increase. During longer-term operation (500-1500 BVs) iron and calcium precipitates were observed, by SEM and EDX analyses, to form in the packed columns. Precipitation led to cementation and reduction in permeability for the Fe(0)/sand media ...

Permeable reactive barriers (PRBs) have become a popular technology for controlling the migration of groundwater contamination away from source zones. System performance models are useful in the design and diagnosis of traditional in situ applications, such as granular zero-valent iron PRBs. Previous efforts to model PRB systems have used either plug-flow or convection-dispersion models to capture the nonuniform flow fields through the system. PRBs that use planar mesh electrodes for the reactive substrate sandwiched between an inert Geonet material (e-barriers), may provide a greater degree of applicability (independence from field conditions) and operating flexibility (easily manipulated reaction rates) than traditional applications. The vast difference in physical configuration between e-barriers and other PRB media is a significant shift in the conceptual model of the hydrodynamic and mass transfer environment within a subsurface implementation. Research using e-barriers to degrade common contaminants has been previously conducted at Colorado State University. Water electrolysis, and subsequent gas generation, has occurred concomitant with contaminant degradation in these studies. Utilizing empirically derived relationships for reactant transport to a gas-evolving electrode and gas-evolution-induced mixing, a general system model was developed. Comparison with experimental results using ferricyanide as a representative contaminant in a laboratory-scale e-barrier demonstrated that incorporating gas generation into the model was necessary for accurate performance predictions as a function of operating conditions. Further insights were obtained by introducing dimensionless variables (Peclet and Damkohler numbers) that could be related for given flow and gas production rates. The model provides a basis for the design of e-barriers and a framework for further research on these systems. The presentation will review reactor operating principles and provide an overview of the process model. Specific performance aspects that will be discussed include how conversion responds to flowrate and gas generation rate. The applicability of this approach to field system design and analysis will also be discussed.

Nanosized zero-valent iron (nZVI) is increasingly gaining interest as an efficient sorbent for various types of aqueous pollutants. In this study, nZVI was synthesised by the borohydride reduction method, characterised and then examined for the removal of aqueous Co 2+ ions over a wide range of concentrations, from 1 to 1000 mg/L. The size of nZVI particles was predominantly within the range of 20-80 nm, and only limited oxidation was observed in samples aged for a period of 2 months. The experiments investigated the effects of V/m ratio, concentration, contact time, repetitive loading, pH and aging on the extent of retardation of Co 2+ ions. Iron nanoparticles demonstrated very rapid uptake and large capacity for the removal of Co 2+ ions. Effective uptake was observed even after a number of repetitive trials. The extent of Co 2+ uptake increased with the increasing pH. X-ray photoelectron spectroscopy (XPS) indicate that the fixation of Co 2+ ions takes place through the interaction of these ions with the oxohydroxyl groups on the iron nanoparticle surfaces in addition to spontaneous precipitate formation at high loadings.

Introduction The nano-scale zero-valent iron (NZVI) was used for the removal of arsenite (As(III)) and arsenate (As (V)) in aqueous solution. Batch experiments were conducted to investigate the effects of initial pH, initial arsenic concentration, dissolved oxygen (DO), and ratio of As(III)/ As(V) on arsenic removal. The NZVI synthesized by using NaBH4 and FeCl3 was put into use right after its synthesis. The arsenic treatment system of recirculation mode consists of a reactor with a liquid volume of 4.4 L, which provides dual function of reactants reaction and particles settling in one unit. Results and discussion Consequently, the pseudo-first order rate equations can be used to describe the removal kinetics for As(V) at pH 4 and 7, while the pseudo-second order reaction was observed for As(V) at pH 9 and As(III) at all pH's studied. Arsenic removal rates of both As(V) and As(III) were lower in the system with lower DO. The rate of As(III) removal decreased with the increase of its initial concentration. In contrast, the removal rate of As(V) still remained significantly high as its initial concentration increased. Conclusions This study reveals that low pH and high DO will favor arsenic removal. With the mixture of As(III) and As(V), the total arsenic was removed faster than solution containing As(III) or As(V) alone. In addition, the mixture with higher fraction of As(V) resulted in higher arsenic removal.

Halogenated organic compounds are common pollutants in groundwater. Consequently, there is widespread interest in understanding the reactions of these compounds in the environment and developing remediation strategies. One area of ongoing research involves the reductive dechlorination of organohalides with zero-valent metals or metal sulfide minerals. These processes have been studied almost exclusively from the perspective of the aqueous phase. In this paper we illustrate the utility of surface analysis techniques, including electron spectroscopies, vibrational spectroscopies, and atomic force microscopy in elucidating the roles played by the surface. A dual analysis approach to the study of reductive dechlorination, combining traditional solution phase analysis with surface analytical techniques, also is demonstrated using a liquid cell coupled to an ultrahigh vacuum surface analysis chamber.

This study investigates, at various scales, the factors that affect the reactivity of granular iron (GI) toward chlorinated solvents and link these scale-specific processes with each other. The Kinetic Iron Model (KIM), provides a separate estimate for both the sorption and reaction processes of contaminant degradation, was used to determine the macro-scale kinetic and sorption parameters in all column experiments associated with this work. The intermediate scale corresponding to pore spaces was investigated by image analysis technique. This technique was used to examine the effects of diluting iron with sand on the availability of reactive iron surface. Two morphological parameters were measured in sections: i) grain perimeter, which reflects surface in contact with solution, and ii) total grain area in section. Morphological analysis showed grain areas exposed in section were highest for 100% iron packings and decreased with increasing sand content. However, the estimated iron grain perimeter length for 85% iron-by weight mixture was found to be the similar to that of 100% iron by weight. This study supported the use of 15% sand (by weight) in iron-sand mixture for the optimum performance of a permeable reactive barrier (PRB). Another pore scale issue examined was the effect of GI packing in column experiments. Among the tested packing variations-vertical packing with long axes preferentially along the flow showed higher reaction rates (2-4 times) compared to packings with long axes preferentially perpendicular to flow (horizontal packing) or randomly arranged (regular packing). The pore-scale differences in grain surface availability to solution through image analysis showed that grain surface availability partially accounted for reactivity differences between columns of different packings. It was suggested that micro-scale changes to the iron surfaces accounted for the remaining differences in reactivity. In order to examine the micro-scale changes that occur on the iron surface due to corrosion and to link these changes with macro-scale KIM parameters, long term column experiments were performed under iv dynamic flow conditions. Micro-scale grain characteristics were made by recovering single grains from sampling port along the length of columns, and examining them through time using Raman spectroscopy and scanning electron microscopy (SEM)/Energy dispersive spectroscopy (EDS). Trichloroethylene (TCE) reduction kinetics showed considerable changes in both TCE sorption and reaction with time. Similarly, spectroscopic studies also indicated profound changes to the iron grain surfaces. It was found that over time, with exposure to TCE and water, iron tended to loose small number of sorption sites associated with highest reactivities (k) whereas large number of less reactive sorption sites increased in number. Raman spectra collected along the column showed the loss of hematite, and transition of intermediate phases to magnetite. Raman signals for surface carbon correspond to declining k values and the nonreactive sorption parameter, suggesting that surface carbon serves as non-reactive sorption sites as well as a reactive one. Further the role of carbon present in GI during reductive dechlorination was assessed by comparing 2 iron types of GI in column experiments: Connelly Iron (GI)(~3% C) and Electrolytic Iron (EI) (≤ 0.01% C). Kinetic data suggested a shift in rate constant (k) and sorption parameters for both iron types with time. This work demonstrated the implication of carbon during the retardation (R app ) of TCE i.e high R app for GI and low for EI. v Above all I would like to pay my warmest thanks to my advisor and mentor, Dr. John Frederick Devlin, for his excellent guidance and support throughout my PhD studies. It was his dedication, encouragement and trust that helped me out in a timely completion of this thesis. His passion to make his students thorough professionals is remarkable. Alongside supervising our research and studies, Dr. Devlin provided me and all of my other colleagues every possible opportunity to interact and collaborate with other scholars, workers and professionals, as available in the field of our studies. This generous and broad minded approach certainly played pivotal role in grooming our skills as competent Geoscientists. It was not only that his office was always a welcome place for me to discuss and sort out any kind of research issues but much more than the superb academic support, that I received from him, the personal cooperation, compassionate understanding and accommodating gestures during the initial days when I and my family came to USA for the first time -particularly with reference to the hardships of raising a young daughter -shall remain to be a memory to cherish in days to come. I also want to express my deep gratitude to my PhD committee members, Dr. Craig P.

En el contexto del tratamiento de aguas contaminadas, este trabajo ofrece una visión general y en profundidad de los últimos avances en diseño racional, síntesis y aplicaciones de nanomateriales magnéticos mesoporosos en la adsorción, oxidación química y reacciones de reducción centradas en la eliminación de contaminantes orgánicos. Se presta especial atención a los materiales magnéticos mesoporosos a base de sílice y carbono. Finalmente, se discuten los desafíos que enfrenta la aplicación de estos materiales en sistemas de tratamiento reales.Within the context of wastewater treatments, this review offers a general and in-depth overview of the latest advances in rational design, synthesis and applications of mesoporous magnetic nanomaterials in adsorption, chemical oxidation and reduction reactions focused on the removal of organic pollutants. Special attention is paid to magnetic mesoporous silica- and carbon-based materials. Finally, the challenges facing the application of these ...

En el contexto del tratamiento de aguas contaminadas, este trabajo ofrece una visión general y en profundidad de los últimos avances en diseño racional, síntesis y aplicaciones de nanomateriales magnéticos mesoporosos en la adsorción, oxidación química y reacciones de reducción centradas en la eliminación de contaminantes orgánicos. Se presta especial atención a los materiales magnéticos mesoporosos a base de sílice y carbono. Finalmente, se discuten los desafíos que enfrenta la aplicación de estos materiales en sistemas de tratamiento reales.Within the context of wastewater treatments, this review offers a general and in-depth overview of the latest advances in rational design, synthesis and applications of mesoporous magnetic nanomaterials in adsorption, chemical oxidation and reduction reactions focused on the removal of organic pollutants. Special attention is paid to magnetic mesoporous silica- and carbon-based materials. Finally, the challenges facing the application of these ...

Fenton's Reagent is an aqueous solution of ferrous ions and hydrogen peroxide. Through laboratory experiments Fenton's Reagent has been shown to be an excellent treatment agent for the removal of organic contaminants dissolved in water. It carries out oxidative degradation of various organic substrates using the principle of advanced chemical oxidation. This is an excellent alternate route for the removal of hazardous and toxic chemicals, which are recalcitrant to biological treatment. The authors of this paper conducted an extensive laboratory investigation to study the degradation of 2,4,6-Trichlorophenol (TCP) using Fenton's Reagent, reported elsewhere 1 . 2 . The results indicated an optimum H202:TCP molar ratio of 5.5: 1 and a Fe 2 +: H202 molar ratio of 0.1: 1 to achieve the best treatment results. The details of the reaction kinetics and mechanism have also been reported 3 . TCP is a RCRA designated hazardous substance, and when present in wastewater, renders it highly toxic to microorganisms for biotreatment process. Only a part of the original substrate is fully oxidized to carbon dioxide and water, while a significant part is partially oxidized to various intermediate products of oxidation. Along with the removal of TCP, treatment by Fenton's Reagent also removes some amount of toxicity associated with TCP. However, the intermediate products also have some toxicity associated with them, the net result being an overall reduction of toxicity of the wastewater. In the study reported in this paper, the toxicity reduction effect of Fenton's Reagent on wastewater contaminated by trichlorophenol, has been demonstrated by subjecting samples of the original substrate and the treated wastewater to a toxicity assay -microtox test. The microtox test results reported an EC50 value of the original substrate of 9.77% and that of the treated wastewater of 29.75%, indicating approximately threefold toxicity reduction. Simultaneous to toxicity reduction, the biotreatability of wastewater also improves significantly after treatment by Fenton's Reagent. A set of biotreatability tests was undertaken with the help of a Challenge Respirometer set -up. The results indicated a significant improvement in oxygen uptake rate of a consortium of heterotrophic microorganisms collected from a domestic wastewater treatment plant, as a result of pretreatment by Fenton's Reagent. Similar response was obtained from a carefully preserved autotrophic culture also, using ammonium sulfate as feed substrate. For respirometric study of toxicity, autotrophs are better indicators of toxicity than heterotrophs. From the results obtained from chemical tests and toxicity assays (microtox tests) it has been concluded that treatment by Fenton's Reagent is an excellent pretreatment process for industrial wastewater containing hazardous and recalcitraHL chemicals, e.g. TCP. This process has the potential of being applied on a full scale to manufacturing sites where soil and/or groundwater is contaminated with TCP. Keeping that in view, a conceptual full-scale process has been proposed in this paper. The equipment have been sized on the basis of data obtained from the tests. Finally, a cost analysis has been presented to estimate the projected cost of treatment per gallon of contaminated water.

Nanosized zero-valent iron (nZVI) is increasingly gaining interest as an efficient sorbent for various types of aqueous pollutants. In this study, nZVI was synthesised by the borohydride reduction method, characterised and then examined for the removal of aqueous Co 2+ ions over a wide range of concentrations, from 1 to 1000 mg/L. The size of nZVI particles was predominantly within the range of 20-80 nm, and only limited oxidation was observed in samples aged for a period of 2 months. The experiments investigated the effects of V/m ratio, concentration, contact time, repetitive loading, pH and aging on the extent of retardation of Co 2+ ions. Iron nanoparticles demonstrated very rapid uptake and large capacity for the removal of Co 2+ ions. Effective uptake was observed even after a number of repetitive trials. The extent of Co 2+ uptake increased with the increasing pH. X-ray photoelectron spectroscopy (XPS) indicate that the fixation of Co 2+ ions takes place through the interaction of these ions with the oxohydroxyl groups on the iron nanoparticle surfaces in addition to spontaneous precipitate formation at high loadings.

Heat-activated sodium persulfate eliminates ACE. • Elevated temperatures, acidic pH boost degradation. • Water matrix constituents can hinder degradation. • Eight ACE transformation products (TPs) detected. • Most TPs formed predicted non-toxic by ECOSAR.

Predicting the migration of sequentially degrading reaction products is important for the accurate analysis of subsurface treatment walls and other environmental systems. Recently, it has also been realized that consideration of rate-limited sorption may be necessary to quantify the transport of contaminants in reactive treatment walls. In this paper, analytical and semianalytical solutions are developed for the one-dimensional transport of a parent compound and three sequentially decaying reaction products influenced by nonequilibrium sorption. The solutions are based on the Laplace transformation technique and incorporate a different sorption distribution coefficient and mass transfer rate for each reaction product. Two types of exit boundary conditions are considered: semi-infinite and finite zero-gradient. The developed solutions are used to simulate the migration of trichloroethylene and its reaction products in a zero-valent iron treatment wall. The effect of nonequilibrium sorption on the time to reach steady state is investigated, and it is shown that a zero-valent iron treatment wall may exhibit a significant transient period. However, concentrations reach 80% of the steady state values within the first 100 pore volumes. It is also shown that neglecting dispersion may lead to nonconservative predictions of the effluent contaminant concentrations. 1.

Sulfate is ubiquitous in groundwater, with both natural and anthropogenic sources. Sulfate reduction reactions play a significant role in mediating redox conditions and biogeochemical processes for subsurface systems. They also serve as the basis for innovative in situ methods for groundwater remediation. An overview of sulfate reduction in subsurface environments is provided, along with a brief discussion of characterization methods and applications for addressing acid mine drainage. We then focus on two innovative, in situ methods for remediating sulfatecontaminated groundwater, the use of zero-valent iron and the addition of electron-donor substrates. The advantages and limitations associated with the methods are discussed, with examples of prior applications.

Research was conducted to examine the effects of various fractions of cosolvent solutions on dechlorination of toxaphene by zero-valent iron (Fe 0 ). Experimental results showed that toxaphene degradation in solution was found to be the result of dechlorination at the Fe 0 surface. The rate of toxaphene dechlorination was also found to reduce with the increase of cosolvent in solution, as the cosolvent presence caused a reduction in toxaphene adsorption to Fe 0 surfaces. Toxaphene sorption to Fe 0 was found to correspond to a Freundlich nonlinear sorption equation and indicated that the linearity of this isotherm in the presence of cosolvent was related to the saturation of solution, which was the ratio of aqueous concentration to the solubility (C a /S c ). When C a /S c > 0.2, the sorption isotherm was almost linear and the concept of cosolvency power can be applied mathematically to describe this process. A mathematical model detailing the sorption and dechlorination of toxaphene by Fe 0 was developed, and showed that experimental data agreed with the theoretically derived data. Overall, results indicated that dechlorination of complex chlorinated substances, such as toxaphene, by Fe 0 can be greatly dependent upon adsorption to the iron surface.

Herein, we synthesized different metal sulfide-coated iron nanoparticles and systematically investigated their reactivity and bactericidal properties. The particles showed a significantly higher reduction efficiency for trichloroethylene and lower bacterial toxicity compared to bare nanoscale iron.

h i g h l i g h t s Granular metallic iron (Fe 0) is a powerful material for water treatment. Methylene blue (MB) discoloration eases Fe 0 testing at lab scale. Early MB breakthrough is documented is systems with large Cl À levels. In the long term, MB discoloration is enhanced in the presence of chloride ions (Cl À). MB discoloration is recommended for characterizing the effects of PO 4 3À , SO 4 2À , etc.

Characterizing the ion-selective nature of Fe 0-based systems using azo dyes: batch and column experiments 60 pages, 23 figures, 9 tables, 140 references II Acknowledgement I would like to express my gratitude to my supervisor PD. Dr. Chicgoua Noubactep for understanding my interest in the field of water treatment and providing me with technical support that added considerably to my graduate experience. Due to his understanding and patience, he became more of a mentor and a friend than a supervisor. I would further like to express my appreciation to my second supervisor PD. Dr. Tobias Licha for his assistance and giving me the opportunity to work in the laboratory. I also express my warm thanks to Dr. Azizur Rahman for his immense guidance and support during my thesis. I would like to acknowledge my friends, Apoorv Jyoti, Nura Abadat for their excellent technical assistance and the useful discussions during the entire course of my thesis.

Arsenic is a toxic semi-metallic element that can be fatal to human health. Membrane filtration can remove a number of contaminants from water, including arsenic. Removal of arsenic by membrane filtration is highly dependent on the species of arsenic and the properties of the membrane. The performance of the nanofilter is better for removing As(V) than As(III). About 57% of As(III) and 81% of As(V) was removed from 500 µg/L arsenic solutions by nanofiltration (NTR729HF, Nitto Denko Corp., Japan) of 700 molecular weight (MW) cutoff. The removal efficiency of microfiltration (MF) was much lower than that of nanofiltration (NF) due to its larger pore size. By comparison only 37% of As(III) and 40% of As(V) were removed by microfiltration (PVA membrane, Pure-Envitech, Korea). However, the removal efficiency of microfiltration was increased dramatically when a small amount of nanoscale zero valent iron (nZVI) was added. The removal efficiency by MF increased up to 90% with As(V) and 84% with As(III) when an amount of 0.1 g/L of nZVI was added into the arsenic solution.

Trichloroethylene (TCE), belonging to the class of Dense Non-Aqueous Phase Liquids (DNAPLs), is a contaminant which is very persistent and widespread in groundwater because of its massive industrial use in past decades (i.e. in the metallurgical, textile and dye production industries). Among the in situ remediation technologies for the recovery of groundwaters polluted by chlorinated solvents, zero-valent iron Permeable Reactive Barriers (PRBs) have a primary importance; this technique, developed in Canada in the nineties, is based on the reductive action of zero-valent iron in a dechlorination process. The PRB is set perpendicularly to the groundwater flow direction, and chlorinated solvents are converted to non-toxic products, such as alkanes and alkenes, through various reaction pathways. In this work a zero-valent iron PRB is proposed as a cleanup methodology for the polluted groundwater of a site near Turin (Northern Italy), used in the past as an industrial landfill for the waste coming from a cast iron foundry. A zero-valent iron (Connelly iron, purchased from Environmental Technologies Inc., Canada), after characterization by means of particle-size and chemical analyses, was evaluated as reactive material. A leaching test, to verify the environmental impact of the material on the groundwater, was also performed on Connelly iron. Batch and column laboratory tests were performed using at first distilled water, and then an aqueous phase with a chemical composition similar to the polluted groundwater. The degradation mechanisms of TCE, hypothesizing a first order kinetic, were discussed, and the values of the kinetic constant and the necessary residence time in the PRB (the period necessary to lower the pollutant concentration below the Italian law limits for groundwater) obtained from the batch and column tests were compared and discussed.

The objective of this study is to exmnine the removal of a priority chlorinated aromatic pollutant, 2,4,6-Trichlorophenol (TCP), in aqueous solution by using Fenton s Reagent (a mixture of hydrogen peroxide and ferrous iron catalyst). Chlorinated phenols are priority pollutants, regulated by stringent discharge litnits. The presence of chlorine increases the toxicity of these phenolic Test results, shown in Figure 2, indicate that the higher the molar ratio of H202 to TCP, the faster the release of chloride from TCP. However, chloride concentrations in all reactors eventually approach the same level of theoretical chloride concentration, about 26.62 mg/L. This process of dechlorination is essentially complete in about two hours. On the basis of HPLC and GC/MS analyses, it was also observed that TCP was almost entirely removed in two hours as dechlorination was completed. The TCP removal also appeared to parallel the release of chloride. Several intermediate peaks were detected by HPLC and GC/MS, but were not identified conclusively at this time. In the experiment using the molar ratio of 2. 75, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) were also determined. Within about two hours, COD was reduced by about 50% while TOC essentially remained unchanged; this implies that TCP might be transformed to other organic intermediates when oxidation and dechlorination took place. Both COD and TOC also appeared to further decrease with time, approaching 85% removal in three months.

Hazardous wastes contaminated by heavy metals, arsenic, and other toxic metals were previously discharged to unlined landfills in and around industry compounds and mining facilities, or near town human lives. These wastes often provoke environmental pollution to groundwater, soils, and other local geologic units which causes serious health risk. In order to prevent the environmental pollution, natural zeolites and clay minerals with calcium compounds can be applied in two ways: One is mixing treatment of these materials to in situ remedy for toxic metals pollution within wastes. Ion-exchange property of zeolites and adsorption of clay minerals are effective in this treatment, which makes geochemically very stable state that reduces leaching of the toxic metals. The other is more physical way, that is a use of a mixture of clay minerals and natural zeolites for liner materials at solid waste disposal site of which impermeable property as well as adsorption successfully shields migration of toxic metals from waste sites. In this paper we report typical results of laboratory experiment and a case study of the remediation techniques by using natural zeolites and clay minerals in solid waste disposal sites in Japan.

In this study, removal efficiency of the Reactive blue 50 and adsorption mechanism on the zero valent iron were investigated. Reactive blue 50 which is used to wool and cashmere dyeing were selected due its non-biodegradable and metabolic stability. Zero valent iron particle has been synthesized by chemical method. A systematic characterization of zero valent iron was performed using X-ray diffractometer, scanning electron microscope and infrared spectrometer analysis. The optimal condition of adsorption was determined as initial reactive dye 50 concentration of 150 mg•L-1 , zero valent iron mass of 0.2 g and solution pH of 6.0 at room temperature. At optimal condition, organic dye removal in a real wastewater sample from Tsombon Knit LLC was 99.5%.

Emerging contaminants are widely detected and persistent in environmental waters. Advanced oxidation processes are among the most effective methods for removing emerging contaminants from water; however, high energy consumption greatly increases the operating costs and limits large-scale applications. In this study, a passive treatment system consisting of four columns packed with mixtures of silica sand, zero-valent iron (ZVI), biochar (BC), and a mixture of (ZVI + BC) were evaluated for simultaneous removal of eight pharmaceuticals, four artificial sweeteners, and two perfluoroalkyl substances (PFASs) from water. Overall, the passive treatment system was more effective for removing target pharmaceuticals (almost complete removal) than artificial sweeteners and PFASs (partial removal). Columns ZVI, BC, and (ZVI + BC) exhibited similar effective removal (>97%) of target pharmaceuticals, including carbamazepine, caffeine, sulfamethoxazole, 3,4-methylenedioxyamphetamine, 3,4methylenedioxymethamphetamine, ibuprofen, gemfibrozil, and naproxen, from ~9 to < 0.25 µg L-1 ; pharmaceuticals were more rapidly removed by Columns ZVI and (ZVI + BC) than Column BC, except for ibuprofen. Column ZVI was more effective for removing artificial sweeteners acesulfame-K and sucralose than Columns BC and (ZVI + BC); however, BC exhibited relatively greater removal of saccharin than ZVI and (ZVI + BC). Acesulfame-K and saccharin (~110 µg L-1) were partially removed in the treatment columns. Cyclamate was not removed in any of the columns. However, more than 76% of input sucralose (~110 µg L-1) was removed in the three treatment columns. Reactive medium BC alone was more effective for removing target PFASs than ZVI and (ZVI + BC). Input perfluorooctanoic acid (PFOA) (~45 µg L-1) was partially removed in the columns containing BC but not ZVI alone. Between 10 and 80% of input

PRBs are engineered systems that provide passive interception and in situ treatment of contaminated groundwater. Within the past decade, PRBs have been applied for the control and remediation of a range of organic and inorganic contaminants in groundwater. In recent laboratory batch and dynamic column tests, a selection of reactive materials that effectively attenuate dissolved arsenic in groundwater to low levels (<0.01 mg/L) have been identified. Basic oxygen furnace (BOF) slag promotes the oxidation of As(III) to As(V), which is subsequently sorbed to the BOF surface. Activated alumina also removes arsenic by the sorption of both As(III) and As(V). Zero-valent iron (ZVI) reduces As(V) to As(III), which is subsequently removed from solution by coprecipitation. In groundwater containing sulfate, ZVI and mixtures containing organic carbon can promote sulfate reduction and the subsequent precipitation of sparingly soluble arsenic and other metal sulfides. The laboratory tests have been conducted using neutral and low pH groundwater, with arsenic concentrations of as much as 4 mg/L. Groundwater chemistry, contaminant flux, the required duration for treatment, and costs for materials and installation will influence the selection of specific media for field-scale PRBs. Blowes et al. (1999ab) provide detailed documentation of the installation and performance of a zero-valent iron PRB that was installed at Elizabeth City, NC, to remediate chromium (VI) and several chlorinated solvents in groundwater. The PRB was installed in 1996 in cooperation with the United States Environmental Protection Agency and the United States Coast Guard. The PRB was installed in a continuous trench approximately 46 m long, 7 m deep and 0.6 m in thickness in the direction of groundwater flow. Influent concentrations of Cr(VI) have been as high as 5 mg/L, but removal of chromium to non-detectable levels (<0.0025 mg/L) has been achieved since installation of the PRB. In fact, Cr(VI) was not detected in multi-level monitors approximately 0.01 m into the zero-valent iron zone during the first three years of monitoring. Eh conditions were strongly reducing and pH increased from approximately 6.5 up-gradient to between 9 and 11 within the PRB. Laboratory investigations indicated the removal mechanism for Cr(VI) was abiotic and was achieved by reduction to Cr(III) and the precipitation as Cr(III) oxyhydroxide or co-precipitation with iron oxyhydroxide

Recebido em 1/9/06; aceito em 15/2/07; publicado na web em 30/7/07 TREATMENT OF GROUNDWATER CONTAMINATED WITH CHLORINATED COMPOUNDS USING ELEMENTAL IRON AND FENTON'S REAGENT. The remediation of groundwater containing organochlorine compounds was evaluated using a reductive system with zero-valent iron, and the reductive process coupled with Fenton's reagent. The concentration of the individual target compounds reached up to 400 mg L-1 in the sample. Marked reductions in the chlorinated compounds were observed in the reductive process. The degradation followed pseudo-first-order kinetics in terms of the contaminant and was dependent on the sample contact time with the solid reducing agent. An oxidative test with Fenton's reagent, followed by the reductive assay, showed that tetrachloroethylene was further reduced up to three times the initial concentration. The destruction of chloroform, however, demands an additional treatment.

The aim of this research was to study the potential of synthesized nanoscale zero-valent iron for nitrate reduction in aqueous solution. Batch technique was used to determine the kinetics and effective parameters. The effects of initial pH level, initial nitrate concentration and nanoscale Fe° concentration on nitrate reduction were studied. Nanoscale zero-valent iron was synthesized by chemical reduction method. The TEM image showed that synthesized nano Fe° has a size in the range of 40-120 nm. Experimental results exhibited that reduction efficiency of nitrate decreases with increasing initial pH and increases significantly due to increasing the concentration of zero-valent iron nanoparticles. Also, it was illustrates that initial concentration of nitrate has little effect on the nitrate reduction efficiency. Under acidic and neutral conditions, pH level of the reaction solution increased considerably after 60 min. However, under alkaline conditions, pH level of the reaction solution decreased. The reduction rate of nitrate reached 80% in 60 min with nanoscale Fe° dosage of 1.0 gl and pH 4. The observed reaction rate constant was determined to be 0.0255 1 in min for nanoscale concentration 1.0 gl. The experimental results indicated that the nitrate reduction with 1 1 zero-valent iron nanoparticles do not comply the first-order reaction model with respect to nitrate concentration.

14 4 Abstract: The aim of this research was to study the potential of synthesized nanoscale zero-valent iron for nitrate reduction in aqueous solution. Batch technique was used to determine the kinetics and effective parameters. The effects of initial pH level, initial nitrate concentration and nanoscale Fe° concentration on nitrate reduction were studied. Nanoscale zero-valent iron was synthesized by chemical reduction method. The TEM image showed that synthesized nano Fe° has a size in the range of 40-120 nm. Experimental results exhibited that reduction efficiency of nitrate decreases with increasing initial pH and increases significantly due to increasing the concentration of zero-valent iron nanoparticles. Also, it was illustrates that initial concentration of nitrate has little effect on the nitrate reduction efficiency. Under acidic and neutral conditions, pH level of the reaction solution increased considerably after 60 min. However, under alkaline conditions, pH level of th...

The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. ix x Conversion Factors, Non-SI to SI Units of Measurement Non-SI units of measurement used in this report can be converted to SI units as follows: acres 4,046.873 square meters feet 0.3048 meters gallons (U.S. liquid) 3.785412 liters inches 2.54 centimeters miles (U.S. statute) , .609347 kilometers pounds (mass) 0.4535924 kilograms I Water-Supply Treatment Facility Water is pumped from Wells 410 and 430A to the water-supply treatment facility (WSTF), Building 1383. Prior to entering the primary surge tank located at Building 1383, water from Well 129 is combined with the water Chapter 1 Introduction

The properties of iron metal that make it useful in remediation of chlorinated solvents may also lead to reduction of other groundwater contaminants such as nitro aromatic compounds (NACs). Nitrobenzene is reduced by iron under anaerobic conditions to aniline with nitrosobenzen e as an intermediate product Coupling products such as azobenzene and azoxybenzene were not detected. First-order reduction rates are similar for nitrobenzene and nitrosobenzen e, but aniline appearance occurs more slowly (typical pseudo-first-o rder rate constants 3.5 x 10-2 , 3.4 x 10-2 , and 8.8 x 10-3 min-1 , respectively, in the presence of 33 g/L acid-washed, 18-20 mesh Fluka iron turnings). The nitro reduction rate increased linearly with concentration of iron surface area, giving a specific reaction rate constant (3.9 ± 0.2 x 10-2 min-I m-2 L). The minimal effects of solution pH or ring substitution on nitro reduction rates, and the linear correlation between nitrobenzene reduction rate constants and the square-root of mixing rate (rpm), suggest that the observed reaction rates were controlled by mass transfer of the NAC to the metal surface. The decrease in reduction rate for nitrobenzene with increased concentration of dissolved carbonate and with extended exposure of the metal to a parti.cular carbonate buffer indicate that the precipitation of siderite on the metal inhibits nitro reduction.

Emerging contaminants are widely detected and persistent in environmental waters. Advanced oxidation processes are among the most effective methods for removing emerging contaminants from water; however, high energy consumption greatly increases the operating costs and limits large-scale applications. In this study, a passive treatment system consisting of four columns packed with mixtures of silica sand, zero-valent iron (ZVI), biochar (BC), and a mixture of (ZVI + BC) were evaluated for simultaneous removal of eight pharmaceuticals, four artificial sweeteners, and two perfluoroalkyl substances (PFASs) from water. Overall, the passive treatment system was more effective for removing target pharmaceuticals (almost complete removal) than artificial sweeteners and PFASs (partial removal). Columns ZVI, BC, and (ZVI + BC) exhibited similar effective removal (>97%) of target pharmaceuticals, including carbamazepine, caffeine, sulfamethoxazole, 3,4-methylenedioxyamphetamine, 3,4methylenedioxymethamphetamine, ibuprofen, gemfibrozil, and naproxen, from ~9 to < 0.25 µg L -1 ; pharmaceuticals were more rapidly removed by Columns ZVI and (ZVI + BC) than Column BC, except for ibuprofen. Column ZVI was more effective for removing artificial sweeteners acesulfame-K and sucralose than Columns BC and (ZVI + BC); however, BC exhibited relatively greater removal of saccharin than ZVI and (ZVI + BC). Acesulfame-K and saccharin (~110 µg L -1 ) were partially removed in the treatment columns. Cyclamate was not removed in any of the columns. However, more than 76% of input sucralose (~110 µg L -1 ) was removed in the three treatment columns. Reactive medium BC alone was more effective for removing target PFASs than ZVI and (ZVI + BC). Input perfluorooctanoic acid (PFOA) (~45 µg L -1 ) was partially removed in the columns containing BC but not ZVI alone. Between 10 and 80% of input

The arsenic content in wastewater is of major concern in copper mineral processing. Typically, a complex wastewater treatment is needed with a combination of chemical and physical processes. Electrocoagulation (EC) has shown its potential for arsenic removal due to the formation of ferric hydroxide-arsenate precipitates but the acidic conditions in the wastewater disfavours the hydroxide formation. This work evaluates the feasibility of EC combined with addition of zero valent iron nanoparticles in the treatment process. The results showed that copper smelter wastewater could be treated efficiently with EC and presence of nanoparticles. The treatment with EC or nanoparticles alone was less efficient. Increasing the concentration of nanoparticles during EC did not increase the efficiency accordingly. The arsenic removal was favoured by an increase of the current density during EC but only until a limiting current density; thereafter the anodes got partly passivated.

The aim of this article is characterization of natural zeolite (clinoptilolite) and its application for removal of heavy metals from aqueous solution. Characterization of the natural zeolite from Beli Plast deposit, Kardjali, was conducted using: classical chemical analysis, XRD, SEM/EDS, DTA/TG/DTG, XRF, FTIR and BET. Based on the results of the chemical composition, XRD, SEM/EDS and FTIR analyses, it is evident that the major component of the working material (~ 95%) is clinoptilolite. In fact, the working material is alumino-silicate with high silicate module and it is of clinoptilolite type. The applied material has the specific surface area of 31.3 m 2 /g determined by BET method with nitrogen adsorption. The maximum capacity of clinoptilolite towards zinc, nickel and cobalt removal under the studied conditions is approximately 3.5 mg/g, for copper and manganese is approximately 4.5 mg/g and for lead ions is approximately 30 mg/g. Natural zeolite (clinoptilolite) was used as a potential raw material for the purpose of removal of Cu(II), Zn(II), Mn(II), Pb(II), Co(II) and Ni(II) ions from model solutions. The experimental results were obtained in a laboratory scale batch glass reactor with continuous stirring at 400 rpm. The adsorption of studied heavy metal ions from solution were efficiently onto used adsorbent and approximately 90% from ions were removed from single ion solutions. Generally, it can be concluded that studied clinoptilolite is a potential raw material for effective removal of heavy metals ions from various types of waste waters.