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Calugaru I.L.,Technology Center for Industrial Waste Center Technologique des Residus Industriels | Calugaru I.L.,University of Quebec at Abitibi - Témiscamingue | Neculita C.M.,University of Quebec at Abitibi - Témiscamingue | Genty T.,Technology Center for Industrial Waste Center Technologique des Residus Industriels | And 3 more authors.
Journal of Hazardous Materials | Year: 2016

Intensive research is ongoing for developing low-cost and highly efficient materials in metal removal from contaminated effluents. The present study evaluated dolomite [CaMg(CO3)2], both raw and modified by thermal activation (charring), for Ni and Zn treatment in contaminated neutral drainage (CND). Batch adsorption testing (equilibrium and kinetics) were conducted at pH 6, to evaluate the performance of initial vs. modified dolomite, and to assess potential mechanisms of metal removal. Charring of dolomite led to a rigid and porous material, mainly consisting of CaCO3 and MgO, which showed a sorption capacity increased sevenfold for Zn and doubled for Ni, relative to the raw material. In addition, Freundlich model best described the sorption of the both metals by dolomite, whereas the Langmuir model best described their sorption on charred dolomite. Plausible mechanisms of metal removal include cation exchange, surface precipitation and sorption processes, with carbonate ions and magnesium oxides acting as active centers. Based on these results, charred dolomite seems a promising option for the efficient treatment of Ni and Zn in CND. © 2016 Elsevier B.V.


Gonzalez-Merchan C.,University of Quebec at Abitibi - Témiscamingue | Genty T.,Technology Center for Industrial Waste Center Technologique des Residus Industriels | Bussiere B.,University of Quebec at Abitibi - Témiscamingue | Potvin R.,Technology Center for Industrial Waste Center Technologique des Residus Industriels | And 3 more authors.
Journal of Environmental Chemical Engineering | Year: 2016

The control of cyanide (CN-) concentrations in gold mine effluents, through degradation and recovery/recycling processes, is generally efficient. However, derivatives and by-products, such as thiocyanates (SCN-) and ammonia nitrogen (NH3-N), are poorly treated, and additional steps are required for their complete removal. Although the Fenton-based processes are well known for using environmentally friendly oxidants, their performance in SCN- and NH3-N treatment, with respect to the catalyst type and the generated by-products in mine effluents, is little known. In this context, the objective of the present study was to assess the performance of Fenton/Fenton-like processes for SCN- and/or NH3-N degradation. The role of the reaction time, temperature, molar ratios, and by-products generated was assessed. The treatability testing was performed with three synthetic effluents (solutions) contaminated with NH3-N (42 ± 2 mg/L) and/or SCN- (121 ± 3 mg/L), at 21 °C. One SCN- contaminated solution was also assessed at 4 °C. The results showed that the oxidation kinetics of SCN- and NH3-N were approximately 1.5 times faster for the Fe(III) catalyst relative to Fe(II). At 21 °C, the optimal SCN-:H2O2:Fe(III) molar ratio of 1:3:0.8 led to 84% and 22% of SCN- and NH3-N removal, respectively, whereas at 4 °C the efficiency of SCN- degradation decreased to 73%. In addition, the oxidation of 1 mol of SCN- produced 1.1 and 0.84 mol of SO4 2- and CN-, respectively. Overall, the Fenton-based processes efficiently removed SCN-, but the complete degradation of NH3-N still requires additional treatment. © 2016 Elsevier Ltd. All rights reserved.


Couvidat J.,INSA Lyon | Neculita C.M.,University of Quebec at Abitibi - Témiscamingue | Benzaazoua M.,INSA Lyon | Benzaazoua M.,University of Quebec at Abitibi - Témiscamingue | And 3 more authors.
Journal of Soils and Sediments | Year: 2016

Purpose: Metal mobility in contaminated marine sediments is largely controlled by low-soluble sulfides. In dredged sediments exposed to air and water, geochemical and microbial-mediated processes may enhance the weathering and leaching of hazardous contaminants, especially trace metals. The objective of the present study was to thoroughly characterize and assess the biogeochemical reactivity of marine-dredged sediments. Materials and methods: Two samples of dredged sediments, one stored (to preserve anoxic conditions) and another exposed to the air, were assessed in the perspective of their long-term management. Biogeochemical reactivity was evaluated, especially by a qualitative assessment of aerobic iron- and sulfur-oxidizing bacteria activity. Results and discussion: Despite the high content of total sulfides (2 to 3.5 wt.% S), the acid-volatile fraction was low (4.3 × 10−3 vs. 9.4 × 10−5 g S kg−1 in raw and weathered sediments, respectively), as an indication of the high degree of crystallinity of sulfide minerals present in samples. The raw sediment was reactive, particularly to aerobic bacteria that decreased the pH from 7.0 to 4.2, for neutrophilic sulfur-oxidizing bacteria, and from 4.5 to 2.5, for acidophilic iron-oxidizing, within only 18 days. Even though only neutrophilic sulfur-oxidizing bacteria seem reactive in the aged sediment, they countered the major buffering effect due to the high amount of carbonates. Important differences in the temporal evolution of pH and Eh of the raw and aged sediments support these results. Conclusions: Neutrophilic sulfur-oxidizing bacteria showed to be the most reactive in both sediments. Finally, despite the sharp pH decrease over time, acidophilic bacteria activity does not seem to be particularly enhanced. © 2016 Springer-Verlag Berlin Heidelberg


PubMed | Technology Center for Industrial Waste Center Technologique des Residus Industriels and University of Quebec at Abitibi - Témiscamingue
Type: | Journal: Journal of hazardous materials | Year: 2016

Intensive research is ongoing for developing low-cost and highly efficient materials in metal removal from contaminated effluents. The present study evaluated dolomite [CaMg(CO3)2], both raw and modified by thermal activation (charring), for Ni and Zn treatment in contaminated neutral drainage (CND). Batch adsorption testing (equilibrium and kinetics) were conducted at pH 6, to evaluate the performance of initial vs. modified dolomite, and to assess potential mechanisms of metal removal. Charring of dolomite led to a rigid and porous material, mainly consisting of CaCO3 and MgO, which showed a sorption capacity increased sevenfold for Zn and doubled for Ni, relative to the raw material. In addition, Freundlich model best described the sorption of the both metals by dolomite, whereas the Langmuir model best described their sorption on charred dolomite. Plausible mechanisms of metal removal include cation exchange, surface precipitation and sorption processes, with carbonate ions and magnesium oxides acting as active centers. Based on these results, charred dolomite seems a promising option for the efficient treatment of Ni and Zn in CND.

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