Journal of Hazardous Materials B120 (2005) 113–118 Solvent extraction applied to the recovery of heavy metals from galvanic sludge J.E. Silva a, ∗ , A.P. Paiva b , D. Soares a , A. Labrincha c , F. Castro a a Mechanical Engineering Department, University of Minho, 4800-058 Guimar˜ aes, Portugal b Department of Chemistry and Biochemistry, Centre of Chemistry and Biochemistry, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal c Ceramics and Glass Engineering Department, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal Received 29 September 2004; received in revised form 7 December 2004; accepted 10 December 2004 Abstract In this study, a hydrometallurgical treatment involving the solvent extraction and recovery of some heavy metals from a sulphuric acid leach solution of galvanic sludge, using di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl)-phosphinic acid (Cyanex 272), both diluted in kerosene, has been investigated. The preliminary tests revealed the necessity to remove other metal species than zinc and nickel, contained in the leach solution, and therefore, processes to cement copper and precipitate chromium were then applied to finally obtain a Zn and Ni pregnant solution prior to solvent extraction. For the experimental conditions studied, Cyanex 272 showed a good recovery of Zn after the stripping stage using H 2 SO 4 , but D2EHPA effectively promoted a higher Zn extraction than Cyanex 272 did. The dependence of the solvent extraction method on variables such as pH, contact time and concentration of extractant, as well as the effect of different concentrations of sulphuric acid on stripping, are discussed. The discussion also includes the previous conditions developed to separate the main interfering metallic species from the leach solution in order to improve the extraction and recovery of zinc by solvent extraction. The final objective has been to achieve a solution as pure as possible to recover nickel sulphate. © 2004 Elsevier B.V. All rights reserved. Keywords: Galvanic sludge; Metals extraction; D2EHPA; Cyanex 272 1. Introduction It is extremely important to develop viable ways to recy- cle industrial sludge if either environmental or economical concerns are to be taken into account. Among the Portuguese industries, galvanic plants are usually those where the envi- ronmental problems caused by their effluents have serious repercussions. However, due to the actual economical condi- tion of the country and also to the fact that the majority of these enterprises exhibit a small or medium dimension, this matter has rarely been considered a national priority to solve. ∗ Corresponding author. Tel.: +351 253 510 220; fax: +351 253 516 007. E-mail addresses: eudes@dem.uminho.pt (J.E. Silva), appaiva@fc.ul.pt (A.P. Paiva), jal@cv.ua.pt (A. Labrincha). Nowadays, however, a lot of waste producers have begun to pay a greater attention to these effluent problems, trying to solve them as better as possible, due to the rising and stringent environmental regulations determined by an effective control policy. Unfortunately, the usual way to overcome the problem is frequently the disposal of the sludge as hazardous waste in special landfills located outside Portugal, since these residues do not have an accessible alternative treatment within the country. These wastes contain metals of interest like nickel, copper, zinc and others [1]. This disposal attitude leads to serious disadvantages, as it contributes to a great build up of environmentally hazardous materials on the earth’s crust; on the other side, it does not consider the recovery of the heavy metals for re-use, which might represent an economy of raw materials and potential 0304-3894/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2004.12.008