Affiliation: | aDept. Engenharia Metalúrgica e de Materiais, Universidade Federal de Minas Gerais, Rua Espírito Santo, 35, 2° andar, Centro, 30130-090 Belo Horizonte, MG, Brazil bDept. Engenharia de Minas, Universidade Federal de Minas Gerais, Rua Espírito Santo, 35, 7° andar, Centro, 30130-090 Belo Horizonte, MG, Brazil cCentro de Desenvolvimento da Tecnologia Nuclear (CDTN), CNEN, Campus da UFMG, Pampulha, P.O. Box 941, 30123-970 Belo Horizonte, MG, Brazil |
Abstract: | The selective removal of zinc(II) over iron(II) by liquid–liquid extraction from spent hydrochloric acid pickling effluents produced by the zinc hot-dip galvanizing industry was studied at room temperature. Two distinct effluents were investigated: effluent 1 containing 70.2 g/L of Zn, 92.2 g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9 g/L of Fe and 2 M HCl. The following extractants were compared: TBP (tri-n-butyl phosphate), Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid], Cyanex 301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid] and Cyanex 302 [bis(2,4,4-trimethylpentyl) monothiophosphinic acid]. The best separation results were obtained for extractants TBP and Cyanex 301. Around 92.5% of zinc and 11.2% of iron were extracted from effluent 1 in one single contact using 100% (v/v) of TBP. With Cyanex 301, around 80–95% of zinc and less than 10% of iron were extracted from effluent 2 at pH 0.3–1.0. For Cyanex 272, the highest extraction yield for zinc (70% of zinc with 20% of iron extraction) was found at pH 2.4. Cyanex 302 presented low metal extraction levels (below 10%) and slow phase disengagement characteristics. Reactions for the extraction of zinc with TBP and Cyanex 301 from hydrochloric acid solution were proposed. |