title: Use of complexing agents for effective ion-exchange separation of Co(II)/Ni(II) from aqueous solutions.
abstract: Cation-exchange separation of Co(2+)/Ni(2+) from aqueous solutions using water-soluble complexing agents of ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), and citrate was experimentally studied at 298 K. Experiments were carried out as a function of initial aqueous pH (1.0-6.0), concentration of total metals (1.5-45.0 mol/m(3)), the concentration ratio of two metals (0.1-10) and of complexing agent to the total metals (0-1). It was shown that the exchange selectivity strongly depended on solution pH and was not completely related to the affinity of any metal with the complexing agents. When a certain level of complexing agent was present, highly effective separation could be achieved at an appropriate pH range (for an equimolar metal solution, e.g., pH 2-3 with EDTA and NTA as well as pH>3 with IDA and citrate). The application potential of this method was highlighted for the separation of Co(2+) from binary mixtures in the presence of trace amount of Ni(2+) due to its high selectivity and the smaller amount of the complexing agents needed.
authors.affiliation: Department of Chemical Engineering, Yuan Ze University, Chung-Li 320, Taiwan. cejuang@ce.yzu.edu.tw
authors.forename: Ruey-Shin
authors.initials: RS
authors.lastname: Juang
authors.forename: Yi-Chieh
authors.initials: YC
authors.lastname: Wang
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D002852:Chromatography, Ion Exchange / Q000379:methods*; D003035:Cobalt / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
chemical_list: D002614:Chelating Agents; D014874:Water Pollutants, Chemical; D003035:Cobalt; D009532:Nickel