An optimization on heavy metals extraction and stripping process using ionic liquids and octanol

Abstract

lonic liquids are regarded as green solvents due to their nonvolatile and stable properties. In this work, 1-Butyl-2,3-dimethylimidazolium chloride and tri-n-octylphosphine oxide were used as carrier and octanol as diluent for extraction of nickel and cadmium ions. The results of face centered composite design (FCCD) revealed that after 6 hours of extraction using 1- butyl-2,3-dimethylimidazolium chloride, 43% cadmium and 18% of nickel were extracted when feed phase pH was set up at 2, but tri-n-octylphosphine oxide showed better efficiency for cadmium extraction, extracting 65% of cadmium ions at pH 2 for the same operational time. However, it was revealed that tri-n-octylphosphine oxide in octanol cannot be considered as a good extractant, resulting in only 8% of nickel ions extraction. Nickel and cadmium stripping condition were analyzed and optimized using NaOH as stripping agent. It was revealed that at 10.5<pH<11 up to 93% of metal can be stripped off from the organic phase, due to precipitation and decomplexation.