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Remediation of chromite ore processing residue using ferrous sulfate and calcium polysulfide
Mahmoud Wazne,Deok Hyun Moon,Santhi Chandra Jagupilla,Sarath Chandra Jagupilla,Christos Christodoulatos,Dimitris Dermatas,Maria Chrysochoou 한국지질과학협의회 2007 Geosciences Journal Vol.11 No.2
Batch tests were conducted to assess the potential use of ferrous sulfate and calcium polysulfide for the remediation of chromite ore processing residue (COPR). The remediation process entails addition of ferrous sulfate or calcium polysulfide to chemically reduce hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] in slurry form and pH adjustment to precipitate Cr(III) as chromium hydroxide. The present study investigates the effects of COPR particle size, treatment pH, and chemical dosage on the performance of the treatment. Smaller particle size resulted in increases in alkaline digestion and Toxicity Characteristic Leaching Procedure (TCLP) Cr(VI) concentrations for the untreated samples. The chemical reduction of Cr(VI) with ferrous iron and sulfides was non-stoichiometric. Four times the stoichiometric amount of ferrous iron or two times the stoichiometric amount of polysulfide were needed to meet both the New Jersey Department of Environmental Protection (NJDEP) regulatory limit of 240 mg/kg for Cr(VI) and EPA TCLP regulatory limit of 5 mg/L for chromium [Cr]. pH adjustment was necessary to prevent the formation of ettringite, a swell causing mineral, upon the introduction of sulfate to the COPR material via ferrous sulfate or calcium polysulfide. The slow hydration of some COPR minerals caused the pH of the treated COPR to creep upward during the curing period. However, when sufficient acid was added, the pH value was controlled at less than 9.27 for a curing period of 1.5 years, which prevented the formation of ettringite.
Impact of brownmillerite hydration on Cr(VI) sequestration in chromite ore processing residue
문덕현,Mahmoud Wazne 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.3
Experimental and modeling studies were conducted to delineate the reaction progress of chromite ore processing residue (COPR) upon hydration and the roles of brownmillerite and calcium aluminum chromium oxide hydrates (CAC) in the scavenging of hexavalent chromium. A kinetic study was conducted by preparing slurry samples with both synthetic brownmillerite and actual COPR samples at ambient temperatures. The hydration reaction of brownmillerite using synthetic brownmillerite was very fast (within 1 hour) and was completed within 2 days. However, the hydration of brownmillerite embedded in COPR to its hydration byproducts was not clearly observed after 7 days of aging. Newly formed Ca_4Al_2O_6(CrO_4)•14H_2O (CAC-14) was observed after 1 hour of aging in both samples. However, the rate of formation of CAC-14 with synthetic brownmillerite was much faster than the COPR embedded brownmillerite. The reaction progress of synthetic brownmillerite and COPR upon chromate influx was simulated by a reaction path modeling program. The phase transformation of both samples can be predicted by the constructed model. Moreover, the formation of CACs upon chromate addition was predicted by the model, suggesting an effective sink for Cr(VI)
Stabilization of As-, Pb-, and Cu-contaminated soil using calcined oyster shells and steel slag.
Moon, Deok Hyun,Wazne, Mahmoud,Cheong, Kyung Hoon,Chang, Yoon-Young,Baek, Kitae,Ok, Yong Sik,Park, Jeong-Hun Ecomed 2015 Environmental Science and Pollution Research Vol.22 No.14
<P>In this study, As-, Pb-, and Cu-contaminated soil was stabilized using calcined oyster shells (COS) and steel slag (SS). The As-contaminated soil was obtained from a timber mill site where chromate copper arsenate (CCA) was used as a preservative. On the other hand, Pb- and Cu-contaminated soil was obtained from a firing range. These two soils were thoroughly mixed to represent As-, Pb-, and Cu-contaminated soil. Calcined oyster shells were obtained by treating waste oyster shells at a high temperature using the calcination process. The effectiveness of stabilization was evaluated by 1-N HCl extraction for As and 0.1-N HCl extraction for Pb and Cu. The treatment results showed that As, Pb, and Cu leachability were significantly reduced upon the combination treatment of COS and SS. The sole treatment of SS (10 wt%) did not show effective stabilization. However, the combination treatment of COS and SS showed a significant reduction in As, Pb, and Cu leachability. The best stabilization results were obtained from the combination treatment of 15 wt% COS and 10 wt% SS. The SEM-EDX results suggested that the effective stabilization of As was most probably achieved by the formation of Ca-As and Fe-As precipitates. In the case of Pb and Cu, stabilization was most probably associated with the formation of pozzolanic reaction products such as CSHs and CAHs.</P>
Effects of Natural and Calcined Oyster Shells on Antimony Solubility in Shooting Range Soil
Mahtab Ahmad,옥용식,문덕현,Mahmoud Wazne,김휘중,이영한 한국응용생명화학회 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.4
Waste oyster shells (OS) and calcined oyster shells (COS) were used to treat metal-contaminated shooting range soil,where antimony (Sb) leachability was assessed. Changes in soil pH induced by the amendments strongly influenced Sb leachability. Sb was immobilized by COS most likely due to calcium antimonate precipitation. This is the first time to our knowledge to report that COS can effectively immobilize Sb in the soil.
Effects of Natural and Calcined Oyster Shells on Antimony Solubility in Shooting Range Soil
Ahmad, Mahtab,Moon, Deok Hyun,Wazne, Mahmoud,Kim, Hee Joung,Lee, Young Han,Ok, Yong Sik The Korean Society for Applied Biological Chemistr 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.4
Waste oyster shells (OS) and calcined oyster shells (COS) were used to treat metal-contaminated shooting range soil, where antimony (Sb) leachability was assessed. Changes in soil pH induced by the amendments strongly influenced Sb leachability. Sb was immobilized by COS most likely due to calcium antimonate precipitation. This is the first time to our knowledge to report that COS can effectively immobilize Sb in the soil.
Assessment of soil washing for Zn contaminated soils using various washing solutions
Deok Hyun Moon,Ju-Ry Lee,Mahmoud Wazne,박정훈 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.2
Bench-scale soil washing experiments were conducted to remove Zn from contaminated soils. Various washing solutions including hydrochloric acid (HCl), nitric acid (HNO3), sodium hydroxide (NaOH), oxalic acid (HOOCCOOH2H2O), sulfuric acid (H2SO4), phosphoric acid (H3PO4), and tartaric acid (C4H6O6) were used. The concentration of the washing solutions used in this study ranged from 0.1 M to 2 M with a liquid to solid ratio of 10. The soil washing results showed the following order of washing solution decreasing effectiveness for the removal of Zn: HCl > HNO3 > H2SO4 > H3PO4 > C4H6O6 > HOOCCOOH2H2O > NaOH.