Separation of Fe(III) and Al via tributyl phosphate and 2-octanol in the comprehensive recovery process of metals from hydrochloric acid leaching solution of fly ash

Abstract

The extraction of Fe(III), Al(III), Zn(II), Pb(II), Cu(II) and Hg(II) from hydrochloric acid leaching solution of fly ash by using solvent extraction with 25% (v/v) tributyl phosphate (TBP), 35% (v/v) 2-octanol and 40% (v/v) kerosene was investigated. To achieve the separation of Fe(III) from Al(III), Zn(II), Pb(II), Cu(II) and Hg(II), five-stage counter-current batch simulation test was conducted under the conditions of O/A = 2/1, 25°C, 5min, 3.66 mol/L of HCl, resulting in the extraction efficiencies of Fe(III) as 99.86%; and the separation coefficients, e.g. βFe/Al,βFe/Zn, βFe/Pb, βFe/Cu, βFe/Hgwere ~∞, 1.7 × 104, 1.8 × 104, 2.1 × 104, 6.7 × 103, respectively; in addition, over 99.9% of Fe(III) could be stripped in a six-stage counter-current batch simulation test using 0.1 mol/L HCl. The mechanism of Fe(III) extraction using tributyl phosphate and 2- octanol was discussed according to FT-IR spectra results.