title: Selective extraction of zinc(II) over iron(II) from spent hydrochloric acid pickling effluents by liquid-liquid extraction.
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 70.2g/L of Zn, 92.2g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9g/L of Fe and 2M 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.
authors.affiliation: Department Engenharia Metalúrgica e de Materiais, Universidade Federal de Minas Gerais, Rua Espírito Santo, 35, # 2 andar, Centro, 30130-090 Belo Horizonte, MG, Brazil. sdrocha@demin.ufmg.br
authors.forename: Marcelo Borges
authors.initials: MB
authors.lastname: Mansur
authors.forename: Sônia Denise Ferreira
authors.initials: SD
authors.lastname: Rocha
authors.forename: Fernando Silva
authors.initials: FS
authors.lastname: Magalhães
authors.forename: Jeaneth dos Santos
authors.initials: Jdos S
authors.lastname: Benedetto
mesh_terms: D006851:Hydrochloric Acid / Q000737:chemistry*; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D008669:Metallurgy; D010755:Organophosphates / Q000737:chemistry; D009946:Organothiophosphorus Compounds / Q000737:chemistry; D010721:Phosphinic Acids / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: C523127:Cyanex 272; C523128:Cyanex 302; D007220:Industrial Waste; D010755:Organophosphates; D009946:Organothiophosphorus Compounds; D010721:Phosphinic Acids; D014874:Water Pollutants, Chemical; C513643:bis(2,4,4-trimethylpentyl)dithiophosphinic acid; C009524:tributyl phosphate; D007501:Iron; D015032:Zinc; D006851:Hydrochloric Acid