Patricio Pinto - Academia.edu (original) (raw)

Papers by Patricio Pinto

Research paper thumbnail of Isotope ratio mass spectrometry and spectroscopic techniques for microplastics characterization

Talanta, 2021

Micro- and nano-scale plastic particles in the environment result from their direct release and d... more Micro- and nano-scale plastic particles in the environment result from their direct release and degradation of larger plastic debris. Relative to macro-sized plastics, these small particles are of special concern due to their potential impact on marine, freshwater, and terrestrial systems. While microplastic (MP) pollution has been widely studied in geographic regions globally, many questions remain about its origins. It is assumed that urban environments are the main contributors but systematic studies are lacking. The absence of standard methods to characterize and quantify MPs and smaller particles in environmental and biological matrices has hindered progress in understanding their geographic origins and sources, distribution, and impact. Hence, the development and standardization of methods is needed to establish the potential environmental and human health risks. In this study, we investigated stable carbon isotope ratio mass spectrometry (IRMS), attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy, and micro-Raman spectroscopy (μ-Raman) as complementary techniques for characterization of common plastics. Plastic items selected for comparative analysis included food packaging, containers, straws, and polymer pellets. The ability of IRMS to distinguish weathered samples was also investigated using the simulated weathering conditions of ultraviolet (UV) light and heat. Our IRMS results show a difference between the δ13C values for plant-derived and petroleum-based polymers. We also found differences between plastic items composed of the same polymer but from different countries, and between some recycled and nonrecycled plastics. Furthermore, increasing δ13C values were observed after exposure to UV light. The results of the three techniques, and their advantages and limitations, are discussed.

Research paper thumbnail of Sources, transport, measurement and impact of nano and microplastics in urban watersheds

Reviews in Environmental Science and Bio/Technology, 2020

The growing and pervasive presence of plastic pollution has attracted considerable interest in re... more The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small (< 5 mm) plastic particles known as 'microplastics' (MPs). Their widespread presence may pose a threat to marine organisms globally. Most of the nano and microplastic (N&MP) pollution in marine environments is assumed to originate from land-based sources, but their sources, transport routes, and transformations are uncertain. Information on freshwater and terrestrial systems is lacking, and data on nanoplastic pollution are particularly sparse. The shortage of systematic studies of freshwater and terrestrial systems is a critical research gap because estimates of plastic release into these systems are much higher than those for oceans. As most plastic pollution originates in urban environments, studies of urban watersheds, particularly those with high population densities and industrial activities, are especially relevant with respect to source apportionment. Released plastic debris is transported in water, soil, and air. It can be exchanged between environmental compartments, adsorb toxic compounds, and ultimately be carried long distances, with potential to cause both physical and chemical harm to a multitude of species. Measurement challenges and a lack of standardized methods has slowed progress in determining the environmental prevalence and impacts of N&MPs. An overall aim of this review is to report the sources and abundances of N&MPs in urban watersheds. We focus on urban watersheds, and summarize monitoring methods and their limitations, knowing that identifying N&MPs and their urban/industrial sources is necessary to reduce their presence in all environments.

Research paper thumbnail of Comparison of the efficiency of chitinous and ligneous substrates in metal and sulfate removal from mining-influenced water

Journal of environmental management, 2018

Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high me... more Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high metal content, but also due to its presence in remotely located mine sites with difficult surrounding environments. An alternative to common remediation technologies, is the use of sulfate-reducing bacteria (SRB) to achieve simultaneous sulfate reduction and metal removal in on-site anaerobic passive systems. In these systems, the organic carbon source (substrate) selection is critical to obtaining the desired effluent water quality and a reasonable treated volume. In this study, we evaluated the use of two different substrates: a chitinous product obtained from crushed crab shells, and a more traditional ligneous substrate. We put the substrates, both with and without water pretreatment consisting of aeration and pH adjustment, in anaerobic experimental columns. The treatment with the chitinous substrate was more effective in removing metals (Al, Cu, Fe, Cd, Mn, Zn) and sulfate for a long...

Research paper thumbnail of Assessing metal mobilization from industrially lead-contaminated soils located at an urban site

Applied Geochemistry, 2017

A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), S... more A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), Controlled Acidity Leaching Protocol (CALP), Acid Neutralization Capacity (ANC), and sequential extraction) were applied to three different soils to study the potential mobility of metals into groundwater. Two of these soils were lead (Pb)-contaminated soils (Hotspot 1 and Hotspot 2) collected from an urban site associated with lead smelting and other industrial operations. The third sample (Stockpile) was soil affected by previous contamination in the area, removed from residential properties, stockpiled, and selected to be used as fill material in the studied site. The TCLP and CALP showed that Pb could be released from both hotspots, but were not released in the acidic rainfall extraction fluid of the SPLP. The sequential extraction showed that Pb in the hotspot soils was associated with the carbonate fraction, while As was associated with the Fe and Mn oxides. The stockpile released traces of Pb or As in the TCLP and CALP, but the ANC only released Pb under acidic conditions and the SPLP did not release Pb or As. Overall, the projected repository with Stockpile would not pose imminent danger to groundwater because, under the expected environmental conditions, Pb and As tend to remain in the solid phase.

Research paper thumbnail of Assessing the Impact of Removing Select Materials from Coal Mine Overburden, Central Appalachia Region, USA

Mine Water and the Environment, 2017

The exposure of readily soluble components of overburden materials from surface coal mining to ai... more The exposure of readily soluble components of overburden materials from surface coal mining to air and water results in mineral oxidation and carbonate mineral dissolution, thus increasing coal mine water conductivity. A conductivity benchmark of 300 μS/cm for mine water discharges in the Appalachian region has been suggested to protect aquatic life and the environment. A USGS screening-level leach test was applied to individual strata from three cores collected from a surface mine site in the Central Appalachian region to generate preliminary conductivity rankings, which were used to classify strata for two disposal scenarios: (i) Unmodified Scenario, which included all extracted strata and (ii) Modified Scenario, which excluded 15% (by mass) of the overburden materials with the highest conductivities. We evaluated overburden leaching conductivity using EPA Method 1627 in 18 dry-wet cycles, generating conductivities of 1,020-1,150 μS/cm for the Unmodified Scenario and 624-979 μS/cm for the Modified Scenario. Hence, overburden segregation was successful in reducing the leachate conductivity, but did not reach the proposed benchmark. The leachate was dominated by sulfate in the first four cycles and by bicarbonates in cycles 5-18 in columns with higher sulfur content, while bicarbonates were dominant throughout experiments with lower sulfur content in overburden. The use of conductivity rankings, isolation of potentially problematic overburden strata, and appropriate materials management could reduce conductivity in Central Appalachian streams and other surface mining areas.

Research paper thumbnail of Mechanisms and effectivity of sulfate reducing bioreactors using a chitinous substrate in treating mining influenced water

Chemical Engineering Journal, 2017

Mining-influenced water (MIW) is one of the main environmental challenges associated with the min... more Mining-influenced water (MIW) is one of the main environmental challenges associated with the mining industry. Passive MIW remediation can be achieved through microbial activity in sulfatereducing bioreactors (SRBRs), but their actual removal rates depend on different factors, one of which is the substrate composition. Chitinous materials have demonstrated high metal removal rates, particularly for the two recalcitrant MIW contaminants Zn and Mn, but their removal mechanisms need further study. We studied Cd, Fe, Zn, and Mn removal in bioactive and abiotic SRBRs to elucidate the metal removal mechanisms and the differences in metal and sulfate removal rates using a chitinous material as substrate. We found that sulfate-reducing bacteria are effective in increasing metal and sulfate removal rates and the duration of operation in SRBRs, and that the main mechanism involved was metal precipitation as sulfides. The solid residues provided evidence of the presence of sulfides in the bioactive column, more specifically ZnS, according to XPS analysis. The feasibility of passive treatments with a chitinous substrate could be an important option for MIW remediation.

Research paper thumbnail of Bench-Scale and Pilot-Scale Treatment Technologies for the Removal of Total Dissolved Solids from Coal Mine Water: A Review

Mine Water and the Environment, 2015

Coal mine water (CMW) is typically treated to remove suspended solids, acidity, and soluble metal... more Coal mine water (CMW) is typically treated to remove suspended solids, acidity, and soluble metals, but high concentrations of total dissolved solids (TDS) have been reported to impact the environment at several CMW discharge points. Consequently, various states have established TDS wastewater regulations and the US EPA has proposed a benchmark conductivity limit to reduce TDS impacts in streams near mining sites. Traditional CMW treatment effectively removes some TDS components, but is not effective in removing major salt ions due to their higher solubility. This paper describes the basic principles, effectiveness, advantages, and disadvantages of various TDS removal technologies (adsorption, bioremediation, capacitive deionization, desalination, distillation, electrochemical ion exchange, electrocoagulation, electrodialysis, ion exchange, membrane filtration, precipitation, and reverse osmosis) that have at least been tested in benchand pilot-scale experiments.

Research paper thumbnail of Biosorption of heavy metals from mining influenced water onto chitin products

Chemical Engineering Journal, 2011

Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due t... more Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due to its impact on water contamination caused by low pH and the presence of high concentrations of toxic metals. Chitorem SC-20 ® (raw crushed crab shells containing 40% (w/w) CaCO 3 , 30% protein, 20% chitin, 7% moisture, and 3% ash) and Chitorem SC-80 ® (the chitin polymer containing 88% chitin and 12% moisture) were used to evaluate heavy metals removal from MIW. It was found that SC-20 was very effective at neutralizing the strong acidity of MIW, even at loads as low as 1 g/L the equilibrium pH was neutral. At a load of 2 g/L, SC-20 showed a final pH of 7.94 with almost complete (>99.8%) removal of iron (120 mg/L), lead (1.1 mg/L) and zinc (79 mg/L), along with partial removal of cadmium (96% of 1.3 mg/L), cobalt (54% of 0.78 mg/L), copper (42% of 72 mg/L), and manganese (64% of 52 mg/L) from MIW. Metal removal was achieved primarily by neutralization and precipitation mainly due to the dissolution of the CaCO 3 from the SC-20. SC-80 was used to differentiate the effect of alkalinity and the amount of metal adsorption achievable by the chitin polymer. Lead (up to 1.24 mg/g), cadmium (up to 1.81 mg/g), and cobalt (up to 0.93 mg/g) from single-metal solutions were adsorbed onto the chitin polymer (SC-80). Metal adsorption onto the chitin polymer seemed to have a minor role as a mechanism of metal removal from MIW. Overall, this study demonstrated that crab-shell products can be an important alternative for MIW remediation.

Research paper thumbnail of Evaluation of metal partitioning and mobility in a sulfidic mine tailing pile under oxic and anoxic conditions

Journal of Environmental Management, 2014

Mining-influenced water emanating from mine tailings and potentially contaminating surface water ... more Mining-influenced water emanating from mine tailings and potentially contaminating surface water and groundwater is one of the most important environmental issues linked to the mining industry. In this study, two subsets of Callahan Mine tailings (mainly comprised of silicates, sulfides, and carbonates) were collected using sealed containers, which allowed keeping the samples under anoxic conditions during transportation and storage. Among the potential contaminants, in spite of high concentrations of Cu, Mn, Pb, and Zn present in the solid mine tailings, only small amounts of Mn and Zn were found in the overlying pore water. The samples were subjected to leaching tests at different reduction-oxidation (redox) conditions to compare metal and S mobilization under oxic and anoxic conditions. It was observed that Cd, Cu, Mn, Pb, S, and Zn were mobilized at higher rates under oxic conditions, while Fe was mobilized at a higher rate under anoxic conditions in comparable constant pH experiments. These results suggest that metal mobilization is significantly impacted by redox conditions. When anoxic metal mobilization assessment is required, it is recommended to always maintain anoxic conditions because oxygen exposure may affect metal mobilization. A sequential extraction performed under oxic conditions revealed that most of the metals in the samples were associated with the sulfidic fraction and that the labile fraction was associated with Mn and moderate amounts of Pb and Zn.

Research paper thumbnail of Influence of trace metal distribution on its leachability from coal fly ash

Fuel, 2008

The risks associated with the reuse of coal fly ash in natural environmental settings in terms of... more The risks associated with the reuse of coal fly ash in natural environmental settings in terms of their mobility and ecotoxicological significance is largely determined by: (1) the physicochemical conditions the fly ash is placed under; (2) the total leachable metal content in fly ash and; (3) the distribution or mineralogical fractionation of metals. In this study, we report the mobility of As, Cr, Pb, Fe, Cu and Zn from a single Class F fly ash (CFFA). The influence of pH on metal release was compared to the total leachable metal content, as determined by single and sequential chemical extractions. The results show that the CFFA sample is environmentally safe under natural pH conditions, with metal leaching less than the mandated RCRA limits. The elements Fe, Pb and Cr were moderately soluble at acidic pH and sparingly soluble beyond neutral pH. Arsenic release from CFFA was higher under aggressive pH conditions (pH < 4 and pH > 9) and consistent with its oxyanionic behavior. Partial dissolution of the acid soluble (exchangeable) fraction at acidic pH; desorption of oxyanions at alkaline pH; adsorption and or co-precipitation of metals with iron (hydr) oxides at neutral pH appeared to be the probable mechanisms controlling metal release. While simple EDTA extractions provided good indications of the total leachable amounts, a direct correlation with pH leaching data was impossible as the mineralogical distribution of the metals in the fly ash appeared to play a significant role in their leachability. In the case of Class F fly ash, metal association with Fe-oxide appeared to play a more dominant role in metal release.

Research paper thumbnail of Biosorption of heavy metals from mining influenced water onto chitin products

Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due t... more Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due to its impact on water contamination caused by low pH and the presence of high concentrations of toxic metals. Chitorem SC-20 ® (raw crushed crab shells containing 40% (w/w) CaCO 3 , 30% protein, 20% chitin, 7% moisture, and 3% ash) and Chitorem SC-80 ® (the chitin polymer containing 88% chitin and 12% moisture) were used to evaluate heavy metals removal from MIW. It was found that SC-20 was very effective at neutralizing the strong acidity of MIW, even at loads as low as 1 g/L the equilibrium pH was neutral. At a load of 2 g/L, SC-20 showed a final pH of 7.94 with almost complete (>99.8%) removal of iron (120 mg/L), lead (1.1 mg/L) and zinc (79 mg/L), along with partial removal of cadmium (96% of 1.3 mg/L), cobalt (54% of 0.78 mg/L), copper (42% of 72 mg/L), and manganese (64% of 52 mg/L) from MIW. Metal removal was achieved primarily by neutralization and precipitation mainly due to the dissolution of the CaCO 3 from the SC-20. SC-80 was used to differentiate the effect of alkalinity and the amount of metal adsorption achievable by the chitin polymer. Lead (up to 1.24 mg/g), cadmium (up to 1.81 mg/g), and cobalt (up to 0.93 mg/g) from single-metal solutions were adsorbed onto the chitin polymer (SC-80). Metal adsorption onto the chitin polymer seemed to have a minor role as a mechanism of metal removal from MIW. Overall, this study demonstrated that crab-shell products can be an important alternative for MIW remediation.

Research paper thumbnail of Isotope ratio mass spectrometry and spectroscopic techniques for microplastics characterization

Talanta, 2021

Micro- and nano-scale plastic particles in the environment result from their direct release and d... more Micro- and nano-scale plastic particles in the environment result from their direct release and degradation of larger plastic debris. Relative to macro-sized plastics, these small particles are of special concern due to their potential impact on marine, freshwater, and terrestrial systems. While microplastic (MP) pollution has been widely studied in geographic regions globally, many questions remain about its origins. It is assumed that urban environments are the main contributors but systematic studies are lacking. The absence of standard methods to characterize and quantify MPs and smaller particles in environmental and biological matrices has hindered progress in understanding their geographic origins and sources, distribution, and impact. Hence, the development and standardization of methods is needed to establish the potential environmental and human health risks. In this study, we investigated stable carbon isotope ratio mass spectrometry (IRMS), attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy, and micro-Raman spectroscopy (μ-Raman) as complementary techniques for characterization of common plastics. Plastic items selected for comparative analysis included food packaging, containers, straws, and polymer pellets. The ability of IRMS to distinguish weathered samples was also investigated using the simulated weathering conditions of ultraviolet (UV) light and heat. Our IRMS results show a difference between the δ13C values for plant-derived and petroleum-based polymers. We also found differences between plastic items composed of the same polymer but from different countries, and between some recycled and nonrecycled plastics. Furthermore, increasing δ13C values were observed after exposure to UV light. The results of the three techniques, and their advantages and limitations, are discussed.

Research paper thumbnail of Sources, transport, measurement and impact of nano and microplastics in urban watersheds

Reviews in Environmental Science and Bio/Technology, 2020

The growing and pervasive presence of plastic pollution has attracted considerable interest in re... more The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small (< 5 mm) plastic particles known as 'microplastics' (MPs). Their widespread presence may pose a threat to marine organisms globally. Most of the nano and microplastic (N&MP) pollution in marine environments is assumed to originate from land-based sources, but their sources, transport routes, and transformations are uncertain. Information on freshwater and terrestrial systems is lacking, and data on nanoplastic pollution are particularly sparse. The shortage of systematic studies of freshwater and terrestrial systems is a critical research gap because estimates of plastic release into these systems are much higher than those for oceans. As most plastic pollution originates in urban environments, studies of urban watersheds, particularly those with high population densities and industrial activities, are especially relevant with respect to source apportionment. Released plastic debris is transported in water, soil, and air. It can be exchanged between environmental compartments, adsorb toxic compounds, and ultimately be carried long distances, with potential to cause both physical and chemical harm to a multitude of species. Measurement challenges and a lack of standardized methods has slowed progress in determining the environmental prevalence and impacts of N&MPs. An overall aim of this review is to report the sources and abundances of N&MPs in urban watersheds. We focus on urban watersheds, and summarize monitoring methods and their limitations, knowing that identifying N&MPs and their urban/industrial sources is necessary to reduce their presence in all environments.

Research paper thumbnail of Comparison of the efficiency of chitinous and ligneous substrates in metal and sulfate removal from mining-influenced water

Journal of environmental management, 2018

Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high me... more Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high metal content, but also due to its presence in remotely located mine sites with difficult surrounding environments. An alternative to common remediation technologies, is the use of sulfate-reducing bacteria (SRB) to achieve simultaneous sulfate reduction and metal removal in on-site anaerobic passive systems. In these systems, the organic carbon source (substrate) selection is critical to obtaining the desired effluent water quality and a reasonable treated volume. In this study, we evaluated the use of two different substrates: a chitinous product obtained from crushed crab shells, and a more traditional ligneous substrate. We put the substrates, both with and without water pretreatment consisting of aeration and pH adjustment, in anaerobic experimental columns. The treatment with the chitinous substrate was more effective in removing metals (Al, Cu, Fe, Cd, Mn, Zn) and sulfate for a long...

Research paper thumbnail of Assessing metal mobilization from industrially lead-contaminated soils located at an urban site

Applied Geochemistry, 2017

A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), S... more A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), Controlled Acidity Leaching Protocol (CALP), Acid Neutralization Capacity (ANC), and sequential extraction) were applied to three different soils to study the potential mobility of metals into groundwater. Two of these soils were lead (Pb)-contaminated soils (Hotspot 1 and Hotspot 2) collected from an urban site associated with lead smelting and other industrial operations. The third sample (Stockpile) was soil affected by previous contamination in the area, removed from residential properties, stockpiled, and selected to be used as fill material in the studied site. The TCLP and CALP showed that Pb could be released from both hotspots, but were not released in the acidic rainfall extraction fluid of the SPLP. The sequential extraction showed that Pb in the hotspot soils was associated with the carbonate fraction, while As was associated with the Fe and Mn oxides. The stockpile released traces of Pb or As in the TCLP and CALP, but the ANC only released Pb under acidic conditions and the SPLP did not release Pb or As. Overall, the projected repository with Stockpile would not pose imminent danger to groundwater because, under the expected environmental conditions, Pb and As tend to remain in the solid phase.

Research paper thumbnail of Assessing the Impact of Removing Select Materials from Coal Mine Overburden, Central Appalachia Region, USA

Mine Water and the Environment, 2017

The exposure of readily soluble components of overburden materials from surface coal mining to ai... more The exposure of readily soluble components of overburden materials from surface coal mining to air and water results in mineral oxidation and carbonate mineral dissolution, thus increasing coal mine water conductivity. A conductivity benchmark of 300 μS/cm for mine water discharges in the Appalachian region has been suggested to protect aquatic life and the environment. A USGS screening-level leach test was applied to individual strata from three cores collected from a surface mine site in the Central Appalachian region to generate preliminary conductivity rankings, which were used to classify strata for two disposal scenarios: (i) Unmodified Scenario, which included all extracted strata and (ii) Modified Scenario, which excluded 15% (by mass) of the overburden materials with the highest conductivities. We evaluated overburden leaching conductivity using EPA Method 1627 in 18 dry-wet cycles, generating conductivities of 1,020-1,150 μS/cm for the Unmodified Scenario and 624-979 μS/cm for the Modified Scenario. Hence, overburden segregation was successful in reducing the leachate conductivity, but did not reach the proposed benchmark. The leachate was dominated by sulfate in the first four cycles and by bicarbonates in cycles 5-18 in columns with higher sulfur content, while bicarbonates were dominant throughout experiments with lower sulfur content in overburden. The use of conductivity rankings, isolation of potentially problematic overburden strata, and appropriate materials management could reduce conductivity in Central Appalachian streams and other surface mining areas.

Research paper thumbnail of Mechanisms and effectivity of sulfate reducing bioreactors using a chitinous substrate in treating mining influenced water

Chemical Engineering Journal, 2017

Mining-influenced water (MIW) is one of the main environmental challenges associated with the min... more Mining-influenced water (MIW) is one of the main environmental challenges associated with the mining industry. Passive MIW remediation can be achieved through microbial activity in sulfatereducing bioreactors (SRBRs), but their actual removal rates depend on different factors, one of which is the substrate composition. Chitinous materials have demonstrated high metal removal rates, particularly for the two recalcitrant MIW contaminants Zn and Mn, but their removal mechanisms need further study. We studied Cd, Fe, Zn, and Mn removal in bioactive and abiotic SRBRs to elucidate the metal removal mechanisms and the differences in metal and sulfate removal rates using a chitinous material as substrate. We found that sulfate-reducing bacteria are effective in increasing metal and sulfate removal rates and the duration of operation in SRBRs, and that the main mechanism involved was metal precipitation as sulfides. The solid residues provided evidence of the presence of sulfides in the bioactive column, more specifically ZnS, according to XPS analysis. The feasibility of passive treatments with a chitinous substrate could be an important option for MIW remediation.

Research paper thumbnail of Bench-Scale and Pilot-Scale Treatment Technologies for the Removal of Total Dissolved Solids from Coal Mine Water: A Review

Mine Water and the Environment, 2015

Coal mine water (CMW) is typically treated to remove suspended solids, acidity, and soluble metal... more Coal mine water (CMW) is typically treated to remove suspended solids, acidity, and soluble metals, but high concentrations of total dissolved solids (TDS) have been reported to impact the environment at several CMW discharge points. Consequently, various states have established TDS wastewater regulations and the US EPA has proposed a benchmark conductivity limit to reduce TDS impacts in streams near mining sites. Traditional CMW treatment effectively removes some TDS components, but is not effective in removing major salt ions due to their higher solubility. This paper describes the basic principles, effectiveness, advantages, and disadvantages of various TDS removal technologies (adsorption, bioremediation, capacitive deionization, desalination, distillation, electrochemical ion exchange, electrocoagulation, electrodialysis, ion exchange, membrane filtration, precipitation, and reverse osmosis) that have at least been tested in benchand pilot-scale experiments.

Research paper thumbnail of Biosorption of heavy metals from mining influenced water onto chitin products

Chemical Engineering Journal, 2011

Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due t... more Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due to its impact on water contamination caused by low pH and the presence of high concentrations of toxic metals. Chitorem SC-20 ® (raw crushed crab shells containing 40% (w/w) CaCO 3 , 30% protein, 20% chitin, 7% moisture, and 3% ash) and Chitorem SC-80 ® (the chitin polymer containing 88% chitin and 12% moisture) were used to evaluate heavy metals removal from MIW. It was found that SC-20 was very effective at neutralizing the strong acidity of MIW, even at loads as low as 1 g/L the equilibrium pH was neutral. At a load of 2 g/L, SC-20 showed a final pH of 7.94 with almost complete (>99.8%) removal of iron (120 mg/L), lead (1.1 mg/L) and zinc (79 mg/L), along with partial removal of cadmium (96% of 1.3 mg/L), cobalt (54% of 0.78 mg/L), copper (42% of 72 mg/L), and manganese (64% of 52 mg/L) from MIW. Metal removal was achieved primarily by neutralization and precipitation mainly due to the dissolution of the CaCO 3 from the SC-20. SC-80 was used to differentiate the effect of alkalinity and the amount of metal adsorption achievable by the chitin polymer. Lead (up to 1.24 mg/g), cadmium (up to 1.81 mg/g), and cobalt (up to 0.93 mg/g) from single-metal solutions were adsorbed onto the chitin polymer (SC-80). Metal adsorption onto the chitin polymer seemed to have a minor role as a mechanism of metal removal from MIW. Overall, this study demonstrated that crab-shell products can be an important alternative for MIW remediation.

Research paper thumbnail of Evaluation of metal partitioning and mobility in a sulfidic mine tailing pile under oxic and anoxic conditions

Journal of Environmental Management, 2014

Mining-influenced water emanating from mine tailings and potentially contaminating surface water ... more Mining-influenced water emanating from mine tailings and potentially contaminating surface water and groundwater is one of the most important environmental issues linked to the mining industry. In this study, two subsets of Callahan Mine tailings (mainly comprised of silicates, sulfides, and carbonates) were collected using sealed containers, which allowed keeping the samples under anoxic conditions during transportation and storage. Among the potential contaminants, in spite of high concentrations of Cu, Mn, Pb, and Zn present in the solid mine tailings, only small amounts of Mn and Zn were found in the overlying pore water. The samples were subjected to leaching tests at different reduction-oxidation (redox) conditions to compare metal and S mobilization under oxic and anoxic conditions. It was observed that Cd, Cu, Mn, Pb, S, and Zn were mobilized at higher rates under oxic conditions, while Fe was mobilized at a higher rate under anoxic conditions in comparable constant pH experiments. These results suggest that metal mobilization is significantly impacted by redox conditions. When anoxic metal mobilization assessment is required, it is recommended to always maintain anoxic conditions because oxygen exposure may affect metal mobilization. A sequential extraction performed under oxic conditions revealed that most of the metals in the samples were associated with the sulfidic fraction and that the labile fraction was associated with Mn and moderate amounts of Pb and Zn.

Research paper thumbnail of Influence of trace metal distribution on its leachability from coal fly ash

Fuel, 2008

The risks associated with the reuse of coal fly ash in natural environmental settings in terms of... more The risks associated with the reuse of coal fly ash in natural environmental settings in terms of their mobility and ecotoxicological significance is largely determined by: (1) the physicochemical conditions the fly ash is placed under; (2) the total leachable metal content in fly ash and; (3) the distribution or mineralogical fractionation of metals. In this study, we report the mobility of As, Cr, Pb, Fe, Cu and Zn from a single Class F fly ash (CFFA). The influence of pH on metal release was compared to the total leachable metal content, as determined by single and sequential chemical extractions. The results show that the CFFA sample is environmentally safe under natural pH conditions, with metal leaching less than the mandated RCRA limits. The elements Fe, Pb and Cr were moderately soluble at acidic pH and sparingly soluble beyond neutral pH. Arsenic release from CFFA was higher under aggressive pH conditions (pH < 4 and pH > 9) and consistent with its oxyanionic behavior. Partial dissolution of the acid soluble (exchangeable) fraction at acidic pH; desorption of oxyanions at alkaline pH; adsorption and or co-precipitation of metals with iron (hydr) oxides at neutral pH appeared to be the probable mechanisms controlling metal release. While simple EDTA extractions provided good indications of the total leachable amounts, a direct correlation with pH leaching data was impossible as the mineralogical distribution of the metals in the fly ash appeared to play a significant role in their leachability. In the case of Class F fly ash, metal association with Fe-oxide appeared to play a more dominant role in metal release.

Research paper thumbnail of Biosorption of heavy metals from mining influenced water onto chitin products

Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due t... more Mining influenced water (MIW) emanating from mine sites poses a major environmental concern due to its impact on water contamination caused by low pH and the presence of high concentrations of toxic metals. Chitorem SC-20 ® (raw crushed crab shells containing 40% (w/w) CaCO 3 , 30% protein, 20% chitin, 7% moisture, and 3% ash) and Chitorem SC-80 ® (the chitin polymer containing 88% chitin and 12% moisture) were used to evaluate heavy metals removal from MIW. It was found that SC-20 was very effective at neutralizing the strong acidity of MIW, even at loads as low as 1 g/L the equilibrium pH was neutral. At a load of 2 g/L, SC-20 showed a final pH of 7.94 with almost complete (>99.8%) removal of iron (120 mg/L), lead (1.1 mg/L) and zinc (79 mg/L), along with partial removal of cadmium (96% of 1.3 mg/L), cobalt (54% of 0.78 mg/L), copper (42% of 72 mg/L), and manganese (64% of 52 mg/L) from MIW. Metal removal was achieved primarily by neutralization and precipitation mainly due to the dissolution of the CaCO 3 from the SC-20. SC-80 was used to differentiate the effect of alkalinity and the amount of metal adsorption achievable by the chitin polymer. Lead (up to 1.24 mg/g), cadmium (up to 1.81 mg/g), and cobalt (up to 0.93 mg/g) from single-metal solutions were adsorbed onto the chitin polymer (SC-80). Metal adsorption onto the chitin polymer seemed to have a minor role as a mechanism of metal removal from MIW. Overall, this study demonstrated that crab-shell products can be an important alternative for MIW remediation.