Development of a Process for Copper Recovering from Galvanic Sludges

Abstract:

Galvanic coating processes are based on metal plating baths and are responsible for the production of large amounts of wastewaters. Subsequent physical-chemical treatment of the wastewaters generates solid wastes called galvanic sludges. These sludges have a hazardous character and are often disposed, mainly on landfills, without any economical or environmental benefits. The development of alternatives and viable ways to reduce the environmental impact and recover the valuable metals contained in those sludges such as copper, chromium, nickel or zinc, which content might reach 30% (wt.%, dry weight) are of utmost importance. The present work has been developed in the aim of the project VALMETAIS and proposes a hydrometallurgical process for copper recovery from galvanic sludges produced by Ni/Cr plating plants. This procedure has been developed on laboratory scale and is based on leaching of sludges in sulphuric acid solution followed by copper cementation step, using iron scrap as a precipitating agent. The sludge has been characterized for its chemical and physical properties. Chemical analysis showed a copper concentration of more than 10% (dry base). Preliminary leaching tests in both sulphuric acid and ammoniacal media were performed in order to determine the best operating conditions for this step of the process and to assure the best metal recovery conditions in subsequent separation methods. Sulphuric acid yielded much higher metal ion dissolution when compared with ammoniacal leaching. Optimal experimental leaching parameters were defined as follows: sulphuric acid solution 100 g/l, a solid to liquid ratio of 1:10, stirring speed of 400 rpm at room temperature and under atmospheric pressure. It was found that metals dissolution was almost complete in 30 minutes of reaction time. Extraction rates of 99% for Cu and Ni were obtained under the leaching conditions above mentioned. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO₄), and presents a metal content below 1%. The subsequent extraction of cooper from the obtained solution is achieved by a cementation step with iron scrap. Copper precipitation was performed at a pH of 2 which was achieved through adding new sludge to the filtered leaching solution. Such pH level led to insignificant precipitation of other metals present in the leaching solution, namely chromium. The recovery rate of copper is about 90% and the purity grade of the resulting copper cement enables its application as a commercial product.

• Periodical: Materials Science Forum (Volumes 730-732)
• Pages: 575-580
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.730-732.575
• Online since: November 2012
• Authors: Cândida Vilarinho, Fernando Castro, Filipa Carneiro, André Ribeiro
• Keywords: Galvanic Sludge, Hydrometallurgical Process, Metal Recovery

References

[1] A.M. Bernardes, I. Bohlinger, W. Wuth, Thermal treatment of galvanic sludges for environmental compatibility, J.O.M. (1996) 59-62.

DOI: 10.1007/bf03222894

[2] L. Magalhães, J.E. Silva, F.P. Castro, Labrincha J.A, Physical and chemical characterization of metal finishing industrial wastes, Journal of Environmental Management 75 (2005) 157-166.

DOI: 10.1016/j.jenvman.2004.09.011

[3] F.P Castro, Ecoinert—inertization of metallurgical wastes by stabilization in ceramic products, Technical Report CRAFT Project no. BE-S2-2260 (1999).

[4] J.M. Magalhães, Inertização de lamas galvânicas por incorporação em materiais cerâmicos: estudo dos mecanismos reaccionais, Tese de Doutoramento, Universidade do Minho (2002).

[5] J.M. Magalhães, J.E. Silva, F.P. Castro, J.A. Labrincha, Kinetic study of the immobilization of galvanic sludge in clay-based matrix, Journal of Hazardous Materials B121 (2005) 69–78.

DOI: 10.1016/j.jhazmat.2005.01.022

[6] M. Magalhães, J.E. Silva, F.P. Castro, J.A. Labrincha, Effect of experimental variables on the inertization of galvanic sludges in clay-based ceramics, Journal of Hazardous Materials 106B (2004) 139-147.

DOI: 10.1016/j.jhazmat.2003.11.001

[7] V. Bednarik, M. Vondruska, M. Koutny , Stabilization/solidification of galvanic sludges by asphalt emulsions, Journal of Hazardous Materials B122 (2005) 139–145.

DOI: 10.1016/j.jhazmat.2005.03.021

[8] D.C.R. Espinosa, J.A.S. Tenório, Laboratory study of galvanic sludge's influence on the clinkerization process Resources, Conservation and Recycling 31 (2000) 71–82.

DOI: 10.1016/s0921-3449(00)00072-0

[9] P.G. Ract, D.C.R. Espinosa, J.A.S. Tenório, Determination of Cu and Ni incorporation ratios in Portland cement clinker, Waste Management 23 (2003) 281–285.

DOI: 10.1016/s0956-053x(02)00061-2

[10] A.C. Silva, S.R.H. Castanho – Silicate glasses obtained from fine silica powder modified with galvanic waste addition, Journal non Cryst. Solids 308 (2004) 211-217.

DOI: 10.1016/j.jnoncrysol.2004.08.171

[11] G. Rossini, A.M. Bernardes, Galvanic sludge metals recovery by pyrometallurgical and hydrometallurgical treatment, Journal of Hazardous Materials 131 (2006) 210–216.

DOI: 10.1016/j.jhazmat.2005.09.035

[12] R.N. Szente, O.W. Bender, R.A. Shroeter, Treating electroplating residues with thermal plama, J.O.M. (1998) 32-35.

[13] M.K. Jha, V. Kumar, R.J. Singh, Review of hydrometallurgical recovery of zinc from industrial wastes, Resour. Conserv. Recycl. 33 (2001) 1–22.

DOI: 10.1016/s0921-3449(00)00095-1

[14] F. Veglio, R. Quaresima, P. Fornari, S. Ubaldini, Recovery of valuable metals from electronic and galvanic industrial wastes by leaching and electrowinning, Waste Management 23 (2003) 245–252.

DOI: 10.1016/s0956-053x(02)00157-5

[15] H.P. Rajcevic, A hydrometallurgical process for the treatment of industrial wastes, Plant. Surface Finishing (1990) 22-25.

[16] J.E. Silva, A.P. Paiva, D. Soares, A. Labrincha, F. Castro, Solvent extraction to the recovery of heavy metals from galvanic sludge, Journal of Hazardous Materials B120 (2005) 113-118.

DOI: 10.1016/j.jhazmat.2004.12.008

[17] J.E. Silva, D. Soares, A.P. Paiva, J.A. Labrincha, F. Castro, Leaching behaviour of a galvanic sludge in sulphuric acid and ammoniacal media, Journal of Hazardous Materials B121 (2005) 195–202.

DOI: 10.1016/j.jhazmat.2005.02.008