Alla Marchuk

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Assessment and optimization of As(V) adsorption on hydrogel composite integrating chitosan-polyvinyl alcohol and Fe3O4 nanoparticles and evaluation of their regeneration and reusable capabilities in aqueous media

Science of The Total Environment

Arsenic and fluoride removal from water using bone char

Dissolved arsenic and fluorine species co-occurrence in groundwater is of great global concern du... more Dissolved arsenic and fluorine species co-occurrence in groundwater is of great global concern due to the consequences arising from daily exposure. Millions of people around the world are experiencing health issues as a result of water contamination, especially in developing countries. Therefore, exploring a cost-effective and environmentally friendly adsorbent using waste material has gained great interest in recent years. The use of animal waste from a growing meat industry, provides a sustainable energy source and environmental benefits by reducing the amount of waste material to be disposed. This study developed bone char and its composites using bone waste as the precursor. The initial objective was to study the effect of pyrolysis temperature (500, 650, 800 and 900 °C), variant residence time and purging gas on the characteristics of the bone char samples. The characteristics of these samples were compared using a range of analytical methods, which were used to interpret the mechanism of removal of fluoride (F-), arsenite [As(III)] and arsenate [As(V)] from water. The samples prepared at 900 °C had the highest removal capacity for As(III) and As(V) at 4.21 and 56.79 µg/g, respectively. On the other hand, a pyrolysis temperature of 650 °C was reported as the optimum temperature for the removal of Ffrom water. Using four different isotherm models (Langmuir, Freundlich, Redlich-Peterson and Sips), the experimental data relating to As(III) and As(V) removal from water under optimal conditions was found to follow the Sips and Langmuir model, respectively. The kinetic models were examined at 0.5, 2.5, 5 and 10 mg/L of initial concentration for both As(III) and As(V) using kinetic and diffusion models. It was found that the main controlling rate of the adsorption process was intraparticle diffusion, while pore diffusion's contribution in the adsorption process was limited to the lower concentrations of 0.5 and 2.5 mg/L. The outcome of the study showed that the removal of As(III) and As(V) from water was complex. Bone char was found to have a higher removal capacity of As(III) at higher concentrations (>20 mg/L). Thus, modifications are required to either increase the As(III) uptake by the bone char samples or oxidize them to As(V) to provide higher removal capacities. Certification of Thesis This Thesis is the work of Mrs Susan Alkurdi except where otherwise acknowledged, with the majority of the authorship of the papers presented as a Thesis by Publication undertaken by the Student. The work is original and has not previously been submitted for any other award, except where acknowledged.

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Combined effects of the biochar/biochar composites and water management strategies on the phyto-availability of arsenic in paddy rice soils

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Evaluating the Ability of Bone Char/nTiO2 Composite and UV Radiation for Simultaneous Oxidation and Adsorption of Arsenite

Sustainable Chemistry, 2022

The reuse of waste materials for water treatment purposes is an important approach for promoting ... more The reuse of waste materials for water treatment purposes is an important approach for promoting the circular economy and achieving effective environmental remediation. This study examined the use of bone char/titanium dioxide nanoparticles (BC/nTiO2) composite and UV for As(III) and As(V) removal from water. The composite was produced via two ways: addition of nTiO2 to bone char during and after pyrolysis. In comparison to the uncoated bone char pyrolyzed at 900 °C (BC900), nTiO2 deposition onto bone char led to a decrease in the specific surface area and pore volume from 69 to 38 m2/g and 0.23 to 0.16 cm3/g, respectively. However, the pore size slightly increased from 14 to 17 nm upon the addition of nTiO2. The composite prepared during pyrolysis (BC/nTiO2)P had better As removal than that prepared after pyrolysis with the aid of ultrasound (BC/nTiO2)US (57.3% vs. 24.8%). The composite (BC/nTiO2)P had higher arsenate oxidation than (BC/nTiO2)US by about 3.5 times. Arsenite oxidati...

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Threshold electrolyte concentration for dispersive soils in relation to CROSS

Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium... more Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium adsorption ratio (SAR) is used to parameterise soil sodicity and the effects of sodium on soil structure. However, some natural soils in Australia, and others irrigated with recycled water, have elevated concentrations of potassium and/or magnesium. Therefore, there is a need to derive and define a new ratio including these cations in place of SAR, which will indicate the dispersive effects of Na and K on clay dispersion, and Ca and Mg on flocculation. Based on the differential dispersive effects Na and K and the differential flocculation powers of Ca and Mg, we propose the concept of 'cation ratio of soil structural stability' (CROSS), analogous to SAR. This paper also gives the results of a preliminary experiment conducted on three soils varying in soil texture on hydraulic conductivity using percolating waters containing different proportions of the cations Ca, Mg, K, and Na....

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Potassium in winery waste waters used for irrigation and soil structural decline

Long-term application of winery waste water containing high levels of potassium will lead to buil... more Long-term application of winery waste water containing high levels of potassium will lead to build-up of exchangeable potassium in soils which can cause soil structural problems similar to exchangeable sodium. Conflicting reports on the effect of exchangeable potassium, being either equal to or less than that of sodium, are found in the literature. We investigated the dispersive and flocculating powers of cations viz. Na, K, Mg and Ca on the basis of our concept that the degree of ionicity (or covalency) of clay-cation bonds determine the dispersion and flocculation of soil clays. Our experimental results were in conformity with the theoretical values of flocculating powers of cations. Compared to Na=1, the flocculating power of the other common cations would be K=1.8, Mg=27, and Ca=45. Flocculating power gives the inverse of dispersive effects. Based on these notions, a ratio analogous to the SAR (sodium adsorption ratio), but which incorporates the differential effects of Na and K...

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Threshold electrolyte concentration and dispersive potential in relation to CROSS in dispersive soils

Soil Research, 2012

We have used the newly developed concept of CROSS (cation ratio of soil structural stability) ins... more We have used the newly developed concept of CROSS (cation ratio of soil structural stability) instead of SAR (sodium adsorption ratio) in our study on dispersive soils. CROSS incorporates the differential dispersive powers of Na and K and the differences in the flocculating effects of Ca and Mg. The CROSS of the dispersed soil solutions, from the differently treated soils of three soil types varying in clay content, mineralogy, and organic matter, was highly correlated with the amount of clay dispersed. The relation between CROSS and exchangeable cation ratio depended on soil type, and particularly organic matter and the content and mineralogy of clay. Threshold electrolyte concentration of the flocculated suspensions was significantly correlated with CROSS of the dispersed suspensions. The cationic flocculating charge of the flocculated suspensions, which incorporates the individual flocculating powers of the cations, was significantly correlated with CROSS. However, these types of...

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Nature of the clay - cation bond affects soil structure as verified by X-ray computed tomography

Soil Research, 2012

Non-destructive X-ray computed tomography (µCT) scanning was used to characterise changes in pore... more Non-destructive X-ray computed tomography (µCT) scanning was used to characterise changes in pore architecture as influenced by the proportion of cations (Na, K, Mg, or Ca) bonded to soil particles. These observed changes were correlated with measured saturated hydraulic conductivity, clay dispersion, and zeta potential, as well as cation ratio of structural stability (CROSS) and exchangeable cation ratio. Pore architectural parameters such as total porosity, closed porosity, and pore connectivity, as characterised from µCT scans, were influenced by the valence of the cation and the extent it dominated in the soil. Soils with a dominance of Ca or Mg exhibited a well-developed pore structure and pore interconnectedness, whereas in soil dominated by Na or K there were a large number of isolated pore clusters surrounded by solid matrix where the pores were filled with dispersed clay particles. Saturated hydraulic conductivities of cationic soils dominated by a single cation were depend...

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Cation ratio of soil structural stability (CROSS)

Soil Research, 2011

Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium... more Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium adsorption ratio (SAR) is used to parameterise soil sodicity and the effects of sodium on soil structure. However, some natural soils in Australia, and others irrigated with recycled water, have elevated concentrations of potassium and/or magnesium. Therefore, there is a need to derive and define a new ratio including these cations in place of SAR, which will indicate the dispersive effects of Na and K on clay dispersion, and Ca and Mg on flocculation. Based on the differential dispersive effects Na and K and the differential flocculation powers of Ca and Mg, we propose the concept of ‘cation ratio of soil structural stability’ (CROSS), analogous to SAR. This paper also gives the results of a preliminary experiment conducted on three soils varying in soil texture on hydraulic conductivity using percolating waters containing different proportions of the cations Ca, Mg, K, and Na. The rel...

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Influence of organic matter, clay mineralogy, and pH on the effects of CROSS on soil structure is related to the zeta potential of the dispersed clay

Soil Research, 2013

The high proportion of adsorbed monovalent cations in soils in relation to divalent cations affec... more The high proportion of adsorbed monovalent cations in soils in relation to divalent cations affects soil structural stability in salt-affected soils. Cationic effects on soil structure depend on the ionic strength of the soil solution. The relationships between CROSS (cation ratio of soil structural stability) and the threshold electrolyte concentration (TEC) required for the prevention of soil structural problems vary widely for individual soils even within a soil class, usually attributed to variations in clay mineralogy, organic matter, and pH. The objective of the present study was to test the hypothesis that clay dispersion influenced by CROSS values depends on the unique association of soil components, including clay and organic matter, in each soil affecting the net charge available for clay–water interactions. Experiments using four soils differing in clay mineralogy and organic carbon showed that clay dispersion at comparable CROSS values depended on the net charge (measure...

Clay behaviour in suspension is related to the ionicity of clay–cation bonds

Applied Clay Science, 2011

The behaviour of four clays viz. an illite, a bentonite and two soil clays in relation to their d... more The behaviour of four clays viz. an illite, a bentonite and two soil clays in relation to their dispersivity, zeta potential and mean particle size was investigated to test the hypothesis that water interaction with clays is dictated by the degree of ionicity of clay–cation bonds. The clay particle being considered as an anion with large size and high charge compared to the cations, the polarizability of the cations determine the degree of ionicity or covalency in a clay–cation bond. The ionicity indices of the cations Li+, Na+, K+, Mg2+, Ca2+, Sr2+ and Ba2+ were derived using their ionisation potentials and charge. In all homoionic clays, high and significant relationships between ionicity indices of cations in clay–cation bonds and the clay behaviour such as dispersibility (measured as turbidity of suspensions) and zeta potential confirm that the degree of ionicity in these bonds dictate the water interaction with clay particles leading to their separation from the clay aggregates. This is further confirmed by the relationship between the mean particle sizes of homoionic clays, measured in four types of clays, and the ionicity indices. Transmission electron micrographs of homoionic illites confirm the aggregation of particles in relation to the ionicity of clay–cation bonds. The strong relationship between relative zeta potential and relative turbidity suggests that the surface charge on clays is responsible for the variations in correlations between ionicity indices and clay behaviour among the four types of clays. The derived ionicity indices in the present study predict the clay behaviour in water better than either ionic potentials or Misono softness parameters.

The nature of clay-cation association dictates clay behaviour in aqueous suspensions

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Understanding Clay Mineralogy and Net Negative Charge in Relation to Soil Specific Threshold Electrolyte Concentrations

Exploring interactions of arbuscular mycorrhizal fungi (AMF), rhizobia and root-lesion nematode (Pratylenchus thornei) in mung bean-Could a lack of AMF be a cause of nodulation failure in mung bean?

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Effect of cations on structural stability of salt-affected soils

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Iron modification to silicon-rich biochar and alternative water management to decrease arsenic accumulation in rice (Oryza sativa L.)

Environmental pollution, 2021

Production of rice grains at non-toxic levels of arsenic (As) to meet the demands of an ever-incr... more Production of rice grains at non-toxic levels of arsenic (As) to meet the demands of an ever-increasing population is a global challenge. There is currently a lack of investigation into integrated approaches for decreasing As levels in rice agro-ecosystems. By examining the integrated iron-modified rice hull biochar (Fe-RBC) and water management approaches on As dynamics in the paddy agro-ecosystem, this study aims to reduce As accumulation in rice grains. The rice cultivar, Ishikari, was grown and irrigated with As-containing water (1 mg L-1 of As(V)), under the following treatments: (1) Fe-RBC-flooded water management, (2) Fe-RBC-intermittent water management, (3) conventional flooded water management, and (4) intermittent water management. Compared to the conventional flooded water management, grain weight per pot and Fe and Si concentrations in the paddy pore water under Fe-RBC-intermittent and Fe-RBC-flooded treatments increased by 24%-39%, 100%-142%, and 93%-184%, respectively...

Effect of cation ratio on soil structural stability is related to the zeta potential of dispersed clay

Water interaction with soil aggregates leads to clay swelling and dispersion, resulting in the de... more Water interaction with soil aggregates leads to clay swelling and dispersion, resulting in the deterioration of soil structure with reduction in soil porosity, aeration and water movement. The integrity of soil aggregates depends on the degree of ionicity of clay-cation bonds which determines the interaction of polar water molecules. Based on this, Rengasamy and Marchuk (2011) have proposed, instead of using sodium absorption ratio (SAR), the use of cation ratio of soil structural stability (CROSS) which takes into account the differential effects of Na and K in dispersing soil clays, and the differential effects of Ca and Mg in flocculating soil clays. CROSS (mol0.5 m-1.5) is defined as (Na+0.56K). (Ca+0.6Mg) -0.5. It is calculated from the concentrations of Na, K, Mg and Ca in soil-water extracts. Spontaneously dispersed clay from a number of soils collected from different locations in South Australia containing varying amounts of Na, K, Mg and Ca was highly correlated with CROSS ...

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IONICITY OF CLAY–CATION BONDS IN RELATION TO DISPERSIVE BEHAVIOR OF Mg AND K SOIL CLAYS AS INFLUENCED BY pH

Clays and Clay Minerals

The dispersive behavior dynamics of clay determine soil characteristics such as permeability and ... more The dispersive behavior dynamics of clay determine soil characteristics such as permeability and aggregate stability, and, consequently, crop productivity. Soil dispersion is heavily influenced by the ionicity of clay–cation bonds and has been shown to be related to the net negative charge and pH of the system. Little work has been done, however, which considers these factors together, especially for K and Mg clays. The objective of the present study was to investigate the effect of changing pH on the dispersive behavior of Mg and K homoionic clays, in comparison to Ca and Na clays under equivalent pH conditions. The clay fractions used here were extracted from three soils and have distinctly different mineralogies. These clays were treated to become homoionic with regard to Na, K, Ca, and Mg. Excess salts were removed by dialysis and pH was adjusted to 3, 4, 5, 6, 7, 8, 9, 10, and 11 for all clays, except Mg (pH range 3–7). Clay dispersion-flocculation dynamics were investigated, and the net negative charge, pH, electrical conductivity (EC), and turbidity were measured. Mg has a similar but less flocculative effect than Ca, while K has a similar but less dispersive effect than Na, under similar pH conditions. The dispersive behavior of Na, K, Mg, and Ca homoionic clays was correlated well with the ionicity of clay–cation bonds at equivalent pH, with the degree of clay dispersion being explained by the pH, EC, ionicity, ζ-potential, and mean particle size of the clay–cation system. A predictive model for dispersion was developed with its applicability and limitations discussed.

Inorganic arsenic species removal from water using bone char: A detailed study on adsorption kinetic and isotherm models using error functions analysis

Journal of Hazardous Materials

A fast analytical protocol for simultaneous speciation of arsenic by Ultra-High Performance Liquid Chromatography (UHPLC) hyphenated to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) as a modern advancement in liquid chromatography approaches

Talanta

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) hyphenated to High Performance Liquid Chrom... more Inductively Coupled Plasma Mass Spectrometry (ICP-MS) hyphenated to High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC) are widely used for simultaneous speciation of arsenic (As). Longer retention time resulting in a slow separation is the major drawback of these existing approaches. Besides, fast separations achieved from HPLC based methods have always resulted in poor resolution and baseline separation between peaks. For the first time, the present study aimed to improve the existing HPLC related methods in order to develop a fast analytical protocol based on Ultra-High Performance Liquid Chromatography (UHPLC) hyphenated to ICP-MS detection for simultaneous separation and quantification of arsenite (As(III)), arsenate (As(V)), dimethylarsonate (DMA(V)) and monomethylarsenate (MMA(V)). Two types of ammonium-based mobile phases (i.e. NH4H2PO4 and NH4NO3) were examined at different eluent concentrations and pH to choose the most effective eluent system. Results demonstrated that the mixed mobile phase containing 8.5 mM of NH4H2PO4 and NH4NO3 (1:1) at pH 6.0 is the most effective eluent achieving the separation of As species with improved resolutions within 5 min which is almost a double saving in analysis time per sample compared to the existing methods (9-15 min). Faster separation is analytically cost effective in terms of ICP-MS running cost and energy consumption. Unlike HPLC, UHPLC did not generate a higher column back pressure with increasing flow rate up to 2.5 mL/min resulting in a faster separation with excellent resolution of peaks. Limits of detection for As species were in the range of 0.3-0.5 μg/L. The proposed method was applied to quantify As species present in commercially available rice varieties in Australia and Sri Lanka. Results of speciation analysis indicated that As(III) is the dominant species, ranging from 53 to 100% in the rice grains. The proposed analytical protocol based on UHPLC-ICP-MS provided an accurate and reliable identification and quantification of As species with the advantages of rapid separation, excellent resolution, and low detection limits. Such a recent trend in fundamental research could be a turning point for future environmental and biological research to further improve this strategy for the speciation of other toxic metal(loid)s in food, water and biological samples.

Alla Marchuk

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