Nickel Recovery And Comprehensive Application Of Electroplating Sludge Containing Nickel

More and more electroplating wastewater is generated with rapid development of electroplating industry. The electroplating sludge is one kind of solid wastes from disposal of electroplating wastewater, including various heavy metallic elements. The direct landfill of electroplating sludge not only endangers environment,brings hazard to human health but also results in huge waste of resources. The nickel-plating is widely utilized in industrial production because its high uniformity, wear-resistance and causticity-resistance et al.. During 47 sorts of hazardous wastes specified in China"National Catalogue of Hazardous Wastes", the electroplating sludge containing nickel is listed in the seventeenth, whose sound disposal and resource utilization is focused on presently. Based on the principle of recycling heavy metals of electroplating sludge and achieving sludge harmlessness, this paper studied on nickel recovery and application from the electroplating sludge caused in Mg-Al alloy nickel-plating production process in an enterprise, and put forward two valid technologies of treating the electroplating sludge containing nickel. The first one is to prepare NiCl₂ as nickel-plating raw material, and the second one is to obtain Ni/Cu/Al₂O₃/ZrO₂ composite ceramics and use nickel and copper to realize ceramics toughening.At first, this paper researched components and acid-base property of the electroplating sludge. It indicates:â‘ pH value of the sludge is 8, alkalescence.â‘¡for elements content of the electroplating sludge, Ni is 11.77%, Cu comes second. Also they are mostly in the form of oxides.NiCl₂ was prepared by selective separation method. Firstly, NH4HCO3 solution was used to selectively leach Ni²⁺ and Cu²⁺ of the sludge into coordination ions in the solution. Further, HCl and TAA as selective precipitator was added to make Cu²⁺ precipitated so NiCl₂ solution was gotten. Finally, evaporating and crystallizing the solution derived NiCl₂ crystal. The purity reaches 95.36% and the recovery rate of nickel comes to 92.5%. The preparative NiCl₂ meets the requirement of national electroplating industry, which can be served as nickel-plating electrolyte or nickel anode activator.In view of Cu and Al content being high in the electroplating sludge except Ni, Ni/Cu/Al₂O₃/ZrO₂ composite powder was attained through co-precipitation compound precursor-hydrothermal processing where not only Ni but Cu and Al were recycled. The recovery rate of nickel is up to 95.5%. The fracture toughness of sintered ZrO₂-based composite ceramics Ni/Cu/Al₂O₃/ZrO₂ is 8.52 MPa·m^1/2 and the compressive strength is 51 MPa, which increase by 2.54 times and 1.5 times compared with those of pure ZrO₂ ceramics, respectively. The nickel and copper particles toughen ZrO₂ ceramics.