title: Recovery of Cu(II) by chemical reduction using sodium dithionite: effect of pH and ligands.
abstract: Wastewaters containing Cu(II) and ligands are ubiquitous in various industrial sectors, and efficacy of copper removal processes, especially precipitation, is greatly compromised by ligands. Chemical reduction, being commonly employed for production of metal nanoparticles, is also effective for metal removal. Adjustment of pH and addition of ligands are important to control the particle size in metallic nanoparticle production. Exploiting the fact that ligands and metals coexist in many wastewaters, chemical reduction was employed to treat ligand-containing wastewater in this study. The experimental result shows that depending on pH, type of ligands, and copper:ligand molar ratio, copper could be removed by either the reduction or precipitation mechanism. Almost complete copper removal could be achieved by the reduction mechanism under optimal condition for solutions containing either EDTA (ethylenediaminetetraacetic acid) or citrate ligands. For solutions containing ammonia, depending on pH and Cu:ammonia molar ratio, copper was removed by both precipitation and reduction mechanisms. At pH of 9.0, formation of nano-sized particles, which readily pass through a 0.45 μm filter used for sample pretreatment before residual copper analysis, results in the lowest copper removal efficiency. Both cuprous oxide and metallic copper are identified in the solids produced, and the possible explanations are provided.
authors.affiliation: Department of Water Resources and Environmental Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui district, New Taipei City, 25137, Taiwan E-mail: chiwang@mail.tku.edu.tw.
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Chou
authors.affiliation: Department of Water Resources and Environmental Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui district, New Taipei City, 25137, Taiwan E-mail: chiwang@mail.tku.edu.tw.
authors.forename: Jui-Hsuan
authors.initials: JH
authors.lastname: Yu
authors.affiliation: Department of Water Resources and Environmental Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui district, New Taipei City, 25137, Taiwan E-mail: chiwang@mail.tku.edu.tw.
authors.forename: Yang-Min
authors.initials: YM
authors.lastname: Liang
authors.affiliation: Department of Water Resources and Environmental Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui district, New Taipei City, 25137, Taiwan E-mail: chiwang@mail.tku.edu.tw.
authors.forename: Pin-Jan
authors.initials: PJ
authors.lastname: Wang
authors.affiliation: Department of Water Resources and Environmental Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui district, New Taipei City, 25137, Taiwan E-mail: chiwang@mail.tku.edu.tw.
authors.forename: Chi-Wang
authors.initials: CW
authors.lastname: Li
authors.affiliation: Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Road, Taipei 106, Taiwan.
authors.forename: Shiao-Shing
authors.initials: SS
authors.lastname: Chen
mesh_terms: D011232:Chemical Precipitation; D003300:Copper / Q000737:chemistry / Q000302:isolation & purification*; D004227:Dithionite / Q000737:chemistry*; D004492:Edetic Acid / Q000737:chemistry; D005374:Filtration; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D010084:Oxidation-Reduction; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification
chemical_list: D003300:Copper; D004227:Dithionite; D004492:Edetic Acid; D008024:Ligands; D062065:Wastewater; D014874:Water Pollutants, Chemical