Papers by Rafael M Santos
Land
As a principal part of the atmosphere–lithosphere interface, soil plays a key role in regulating ... more As a principal part of the atmosphere–lithosphere interface, soil plays a key role in regulating the atmospheric CO2 concentration and global climate. Comprising two major pools (carbonate in soils and bicarbonate in groundwater), soil inorganic carbon (SIC) is deemed as the primary carbon (C) sink and source in areas with low mean annual rainfall. SIC may originate from soil parent material or from the formation of secondary carbonate when divalent cations from an extraneous source are supplied. The latter may result in pedogenic carbonate (PC) formation, increasing soil C content and sequestering atmospheric carbon. Since the sequestration of atmospheric CO2 through formation of pedogenic carbonate is gaining popularity as a method to support climate change mitigation efforts and to claim carbon credits, the mechanisms influencing the formation and migration of pedogenic carbonate need to be well understood. The present review provides an overview of the available literature on po...
Crystals, 2021
Canada’s mineral reserves can play a very important role in curbing climate change if natural alk... more Canada’s mineral reserves can play a very important role in curbing climate change if natural alkaline minerals are used for the process of mineral carbonation. In this work, the potential of using two Canadian natural silicates for accelerated carbonation is experimentally assessed: kimberlite mine tailing (Mg0.846Al0.165Fe0.147Ca0.067SiO3.381) from the Northwest Territories, and mined wollastonite ore (Ca0.609Mg0.132Al0.091Fe0.024SiO2.914) from Ontario. The aim of this work was to evaluate the weathering reactivity and CO2 uptake capacity via carbonation of these two comminuted rocks, both of which are made up of a mixture of alkaline minerals, under process conditions that spanned from milder to intensified. Research questions addressed include: does kimberlite contain a sufficient amount of reactive minerals to act as an effective carbon sink; is dehydroxylation necessary to activate kimberlite, and to what extent does it do this; do secondary phases of wollastonite hinder its r...
Abstract. Inorganic waste materials that have the suitable inherent characteristics could be used... more Abstract. Inorganic waste materials that have the suitable inherent characteristics could be used as precursors for the synthesis of micro- and mesoporous materials, which present great potential to be re-utilized as sorbent materials for heavy metal remediation. Three inorganic waste materials were studied in the present work: water treatment residuals (WTRs) from an integrated drinking water/wastewater treatment plant, and fly ash and bottom ash samples from a municipal solid waste incinerator (MSWI). These wastes were converted into three sorbent materials: ferrihydrite-like materials derived from drying of WTRs, hydroxyapatite-like material derived from ultrasound assisted synthesis of MSWI fly ash with phosphoric acid solution, and a zeolitic material derived from alkaline hydrothermal conversion of MSWI bottom ash. The performance of these materials, as well as their equivalent commercially available counterparts, was assessed for the adsorption of multiple heavy metals (As, C...
For many decades, X-ray diffraction (XRD) has been used for material characterization. With the r... more For many decades, X-ray diffraction (XRD) has been used for material characterization. With the recent development in material science understanding and technology, various new materials are being developed, which requires upgrading the existing analytical techniques such that intricate problems can be solved. Although, XRD is a well-established non-destructive technique, it still requires further improvements in its characterization capabilities, especially when dealing with complex mineral structures. The present review conducts comprehensive discussions on atomic crystal structure, XRD principle, its applications, uncertainty during XRD analysis, and required safety precautions, all in one place. It further discusses the future research directions, especially the use of artificial intelligence and machine learning tools for improving the effectiveness and accuracy of XRD technique for mineral characterization. It has been focused that how XRD patterns can be utilized for a thorou...
Education for Chemical Engineers, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACS Omega, 2020
The combination of chemical enhanced oil recovery (CEOR) and low salinity water (LSW) flooding is... more The combination of chemical enhanced oil recovery (CEOR) and low salinity water (LSW) flooding is one of the most attractive enhanced oil recovery (EOR) methods. While several studies on CEOR have been performed to date, there still exists a lack of mechanistic understanding on the synergism between surfactant, alkali and LSW. This synergism, in terms of fluid− fluid interactions, is experimentally investigated in this study, and mechanistic understanding is gained through fluid analysis techniques. Two surfactants, one cationic and one anionic, namely an alkyltrimethylammonium bromide (C 19 TAB) and sodium dodecylbenzenesulfonate (SDBS), were tested, together with NaOH used as the alkali, diluted formation brine used as the LSW, and the crude oil was collected from an Iranian carbonate oil reservoir. Fluids were analyzed using pendant drop method for interfacial tension (IFT) measurement, and Fourier transform infrared spectroscopy for determination of aqueous and oleic phase chemical interaction. The optimum concentration of LSW for IFT reduction was investigated to be 1000 ppm. Additionally, both surfactants reduced IFT significantly, from 28.86 mN/m to well below 0.80 mN/m, but in the presence of optimal alkali concentration the IFT dropped further to below 0.30 mN/m. IFT reduction by alkali was linked to the production of three different types of in situ anionic surfactants, while in the case of anionic and cationic surfactants, saponification reactions and the formation of the C 19 TAOH alcohol, respectively, were linked to IFT reduction. The critical micelle concentration and optimal alkali concentration when using cationic C 19 TAB were significantly lower than with the anionic surfactant; respectively: 335 vs 5000 ppm, and 500 vs 5000 ppm. However, it was found that SDBS was more compatible with NaOH than C 19 TAB, due to occurrence of alkali deposition with the latter beyond the optimal point.
Minerals, 2020
In the world of construction, cement plays a vital role, but despite its reputation and affordabl... more In the world of construction, cement plays a vital role, but despite its reputation and affordable prices, the cement industry faces multiple challenges due to pollution and sustainability concerns. This study aimed to assess the possibility of utilizing carbonated kimberlite tailings, a waste product from diamond mining, as a partial cement substitute in the preparation of concrete bricks. This is a unique opportunity to help close the gap between fundamental research in mineral carbonation and its industrial implementation to generate commercial products. Kimberlite was subjected to a mild thin-film carbonation process in a CO2 incubator at varying levels of CO2 concentration (10 vol% and 20 vol% at ambient pressure), kimberlite paste moisture content (10 wt% to 20 wt%), and chamber temperature (35 and 50 °C). The formation of magnesium carbonates, in the form of nesquehonite and lansfordite, was verified by X-ray diffraction analysis, and total CO2 uptake was quantified by therma...
Reaction Chemistry & Engineering, 2020
A CO2 mineralisation process using brine solutions with a catalyst was investigated from experime... more A CO2 mineralisation process using brine solutions with a catalyst was investigated from experimental and modelling perspectives.
Open Agriculture, 2019
Loss of phosphorus from agricultural land through water runoff causes serious detrimental effects... more Loss of phosphorus from agricultural land through water runoff causes serious detrimental effects on the environment and on water quality. Phosphorous runoff from excessive use of fertilizers can cause algal blooms to grow in nearby water systems, producing toxins that contaminate drinking water sources and recreational water. In this study, a risk analysis of the algal toxin micro-cystin-LR and the mitigation of phosphorus from agriculture runoff is discussed. A risk analysis was performed on the algal bloom toxin microcystin-LR considering the Lake Erie algal bloom event of 2011 as a case study. Toxicity risk analysis results show that relatively low concentrations of microcystin-LR compared to recent case studies pose an acute health risk to both children and adults, and a significant increase in the risk of developing cancer is suggested but subject to further study given the assumptions made. This study investigated the potential of using wollastonite to mitigate phosphorus pol...
ACS Omega, 2019
To lock atmospheric CO 2 at anthropogenic timescale, fast weathering silicates can be applied to ... more To lock atmospheric CO 2 at anthropogenic timescale, fast weathering silicates can be applied to soil to speed up natural CO 2 sequestration via enhanced weathering. Agricultural lands offer large area for silicate application, but expected weathering rates as a function of soil and crop type, and potential impacts on the crops, are not well known. This study investigated the role of plants on enhanced weathering of wollastonite (CaSiO 3) in soils. Using rooftop pot experiments with leguminous beans (Phaseolus vulgaris L.) and nonleguminous corn (Zea mays L.), CO 2 sequestration was inferred from total inorganic carbon (TIC) accumulation in the soil and thermogravimetric analysis, and mineral weathering rate was inferred from alkalinity of soil porewater. Soil amendment with wollastonite promoted enhanced plant growth: beans showed a 177% greater dry biomass weight and corn showed a 59% greater plant height and a 90% greater dry biomass weight. Wollastonite-amended soil cultivated with beans showed a higher TIC accumulation of 0.606 ± 0.086%, as compared to that with corn (0.124 ± 0.053%). This demonstrates that using wollastonite as a soil amendment, along with legume cultivation, not only buffers the soil against acidification (due to microbial nitrogen fixation) but also sequesters carbon dioxide (12.04 kg of CO 2 /tonne soil/month, 9 times higher than the soil without wollastonite amendment).
Journal of CO2 Utilization, 2018
Carbonation of lime (CaO) using ethanol is studied for direct atmospheric CO 2 capture. The param... more Carbonation of lime (CaO) using ethanol is studied for direct atmospheric CO 2 capture. The parameters that control the carbonation of lime using air and ethanol are determined, and operational conditions that enhance the CO 2 uptake are investigated. A mixture of lime and ethanol was exposed to air within a fume hood, allowing ethanol evaporation for a defined period. Results reveal that the carbonation occurs after ethanol has evaporated, when the remaining powder is exposed to the atmosphere. After contact with ethanol, the CO 2 uptake of lime is enhanced because the specific surface area of the powder increases. Increasing the time of exposure to the atmosphere results in an increase in the carbonation conversion (from 0.03 gCO 2 /gCaO for 1 day of exposure, up to 0.44 gCO 2 /gCaO for 60 days of exposure). Milling the solvent-lime slurry, before exposing it to the atmosphere, also enhances the carbonation yield through the effect of size reduction and mechanical activation (from 0.30 gCO 2 /gCaO with 5 min of pre-milling, to 0.60 gCO 2 /gCaO with 10 min of pre-milling). Another way to increase the carbonation yield is through the use of alkaline wastewater. Combining the wastewater with ethanol, or milling a slurry of CaO/wastewater before exposure to the atmosphere, increases the carbonation yield further to 90.2% (0.70 gCO 2 /gCaO) and 96.2% (0.75 gCO 2 /gCaO), respectively. This study reveals that ethanol/alkaline wastewater treatments, along with their different enhancement options, represent an effective viable route for sequestering CO 2 from the atmosphere, which could be applied to pure lime or potentially to lime-containing wastes.
E3S Web of Conferences, 2013
Inorganic waste materials that have the suitable inherent characteristics could be used as precur... more Inorganic waste materials that have the suitable inherent characteristics could be used as precursors for the synthesis of micro-and mesoporous materials, which present great potential to be re-utilized as sorbent materials for heavy metal remediation. Three inorganic waste materials were studied in the present work: water treatment residuals (WTRs) from an integrated drinking water/wastewater treatment plant, and fly ash and bottom ash samples from a municipal solid waste incinerator (MSWI). These wastes were converted into three sorbent materials: ferrihydrite-like materials derived from drying of WTRs, hydroxyapatite-like material derived from ultrasound assisted synthesis of MSWI fly ash with phosphoric acid solution, and a zeolitic material derived from alkaline hydrothermal conversion of MSWI bottom ash. The performance of these materials, as well as their equivalent commercially available counterparts, was assessed for the adsorption of multiple heavy metals (As, Cd, Co, Ni, Pb, Zn) from synthetic solutions, contaminated sediments and surface waters; and satisfactory results were obtained. In addition, it was observed that the combination of sorbents into sorbent mixtures enhanced the performance levels and, where applicable, stabilized inherently mobile contaminants from the waste derived sorbents.
Valorisation of thermal residues by intensified mineral carbonation
Proceedings of the …, 2011
... It is a natural process in the global carbon cycle, producing carbonate minerals that are sta... more ... It is a natural process in the global carbon cycle, producing carbonate minerals that are stable over geologic timescales, and have minimal leakage risk [1]. Typical virgin materials used for mineral carbonation include: olivine (Mg,Fe)2SiO4; serpentine/chrysotile (Mg,Fe)3Si2O5 ...
SMaRT-Pro² is an Industrial Knowledge Platform on the Sustainable Materialization of Residues fro... more SMaRT-Pro² is an Industrial Knowledge Platform on the Sustainable Materialization of Residues from Thermal Processes into Products. It consists of three research institutions and more than 25 partners from industry, government and civil society. The Platform brings together expertise from chemical technology, materials and metallurgical engineering, civil engineering and building technology, applied mineralogy, economy, organization psychology and law. As such it is able to consider the whole implementation chain of sustainable valorization of waste materials, in particular solid residues and carbon dioxide, the two largest and most important waste products from thermal processes. This Knowledge Platform focuses on different types of waste-to-product valorization such as the production of a carbon sink, construction materials, and sorbents. After an introduction to the Platform, the paper will focus on the theme of carbon sink. An overview will be given of the work performed in the ...
In this work, we explore a novel mineral processing approach using carbon dioxide to promote mine... more In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO2 partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation
Environmental Science & Technology, 2021
With no single carbon capture and sequestration solution able to limit the global temperature ris... more With no single carbon capture and sequestration solution able to limit the global temperature rise to 1.5−2.0°C by 2100, additional climate stabilization measures are needed to complement current mitigation approaches. Urban farming presents an easy-to-adopt pathway toward carbon neutrality, unlocking extensive urban surface areas that can be leveraged to grow food while sequestering CO 2. Urban farming involves extensive surface areas, such as roofs, balconies, and vertical spaces, allowing for soil presence and atmospheric carbon sequestration through air-to-soil contact. In this viewpoint we also advocate the incorporation of enhanced rock weathering (ERW) into urban farming, providing a further opportunity for this recognized negative emissions technology that is gaining momentum worldwide to gain greater utilization.
Journal of Environmental Health Science and Engineering, 2019
Production and usage of green and sustainable building materials realizes the desire to integrate... more Production and usage of green and sustainable building materials realizes the desire to integrate more biodegradable, natural, recycled, and renewable resources into the construction industry. The aim is to replace traditionally available construction industry materials due to their environmental impacts through air emissions and waste generation. An observed trend is the production of insulation materials by recycling of industrial, agriculture, construction and demolition (C&D), and municipal solid wastes, thus reducing the environmental burdens of these wastes. While thermal insulation is important in saving energy, sound insulation has drawn much attention in recent years. There are various waste materials that have good thermal and sound properties, enabling effective replacement of traditional materials. This review investigates the use of industrial, agricultural, C&D, and municipal solid wastes to produce innovative thermal and acoustic insulating building materials. The performance of these insulating materials, and the influence of several materials parameters (density, thermal conductivity, sound absorption coefficient) on thermal and acoustic performance are reported after a brief description of each material.
Application of commercial zwitterionic surfactants and ionic liquids to reduce interfacial tension and alter wettability in a carbonate reservoir
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Interfacial tension (IFT) reduction and wettability alteration are major mechanisms to chemically... more Interfacial tension (IFT) reduction and wettability alteration are major mechanisms to chemically enhanced oil recovery (CEOR) in carbonate reservoirs. The purpose of this research was to investiga...
Particle size characterization in mineral carbonation for understanding reaction fundamentals".
Wollastonite is a natural silicate mineral that can be used as an agricultural soil amendment. On... more Wollastonite is a natural silicate mineral that can be used as an agricultural soil amendment. Once in the soil, this mineral undergoes weathering and carbonation reactions, and, under certain soil and field crop conditions, our previous work has shown that this practice leads to accumulation of inorganic carbon (calcium carbonate). Mineral carbonation is the carbon sequestration approach with the greatest potential for sequestration capacity and permanency. Agricultural lands offer vast areas onto which such minerals can be applied, while benefiting crops. This work illustrates a technique to separate wollastonite-containing soils into different fractions. These fractions are characterized separately to determine organic and inorganic content, as well as to determine the chemical and mineral composition. The aim is to detect the fate of wollastonite in agricultural soils, and the fate of weathering/carbonation products in the soil. The soils used in the study were collected from soybean and potato farmlands in Southern Ontario, and from an experimental pilot plot. Soil fractionation was done using sieving, and soil fractions were analyzed by a calcimeter, X-ray diffraction, and loss-on-ignition. Acid digested samples were measured by Inductively Coupled Plasma Mass Spectrometry. Carbonates and wollastonite were enriched by fractionation.
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Papers by Rafael M Santos