title: Toluene/ter-butanol mixed solvent for the selective extraction of Cr(VI) from divalent heavy metals.
abstract: A solvent-extraction system comprising toluene/ter-butanol (ter-BuOH) mixed solvent as the organic phase was developed to selectively extract Cr(VI) from acidic chloride media in the presence of divalent metals, namely Cd(II), Co(II), Cu(II), Ni(II) and Zn(II) under 5 M CaCl2 salting-out conditions. Chromium(VI) was selectively extracted as a solvated ion-pair of [ter-BuOH2+ x CrO3Cl-] at ter-BuOH mole fractions of between 0.1 and 0.6 (9.0-57.2% in volume). Divalent metals were extracted at ter-BuOH mole fraction over 0.6 with extraction percents of Co (< 20%), Cu (< 15%), Ni (< 10%) and Zn (< 20%). The concentrations of Ca2+, water and ter-BuOH in the organic phase and ter-BuOH in the aqueous phase were determined to find out the effects on the extraction of Cr(VI). The chemical species of Cr(VI) in acidic chloride media containing 5 M CaCl2 and 0.1 M HCl was confirmed to be the CrO3Cl- species. The effects of the acid, salt concentrations in the aqueous phase and the solvent composition of a mixed organic solvent on the extraction of Cr(VI) were evaluated. Based on the above studies, the extraction mechanism was elucidated and the optimum extraction conditions were determined.
authors.affiliation: Department of Chemistry, Faculty of Science and Engineering, Saga University, Japan.
authors.forename: Sethsiri S
authors.initials: SS
authors.lastname: Samaratunga
authors.forename: Jun
authors.initials: J
authors.lastname: Nishimoto
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tabata
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D002122:Calcium Chloride / Q000737:chemistry; D002274:Carcinogens, Environmental / Q000032:analysis / Q000737:chemistry; D002413:Cations, Divalent / Q000737:chemistry; D002857:Chromium / Q000032:analysis* / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D005590:Fractional Precipitation; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000737:chemistry; D012462:Saline Solution, Hypertonic; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D014050:Toluene / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry; D020002:tert-Butyl Alcohol / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D002274:Carcinogens, Environmental; D002413:Cations, Divalent; D012462:Saline Solution, Hypertonic; D012996:Solutions; D012997:Solvents; D014867:Water; D002857:Chromium; C074702:chromium hexavalent ion; D014050:Toluene; D003035:Cobalt; D003300:Copper; D009532:Nickel; D015032:Zinc; D002122:Calcium Chloride; D020002:tert-Butyl Alcohol