Abstract:
The selective extraction of Cr(VI) from spent pickling solution of the stainless steel-cold rolled plate process by hollow fiber supported liquid membrane (HFSLM) was investigated. The effects of types of organic extractants, i.e., metyl trioctylammonium chloride (Aliquat 336), tri-n-octylamine (TOA), tri-n-butyl phosphate (TBP) and the mixture of Aliquat 336 and TBP; concentration of the selected extractant; types of stripping solutions (NaCl and NaOH); pH and concentration of the selected stripping solution; and the operating temperature were studied. The feed and stripping solutions flowed counter-currently.
Of the extractants used in this study, Aliquat 336 is a specific carrier to selectively extract Cr(VI) ions. The results show that the coexisting contamination of Fe(III) and Ni(II) ions has no significant effect on Cr(VI) extraction. The percentage of Cr(VI) extraction slightly increases with the concentration and pH of NaCl stripping solution, and temperature (0.1-1 M, 7-12 and 20- 50 ℃). By using the optimum conditions of 5%(v/v) Aliquat 336, 0.5 M NaCl with pH 7 at room temperature, about 70% Cr(VI) is extracted. In addition, the calculated diffusion energy of Cr(VI) extraction is 15.14 kJ/mol.