Recovery and characterization of nickel particles by chemical reduction method from wastes generated in electroless industry

The discarded solutions by the chemical nickel industry have high amounts of nickel, this is why they are considered hazardous wastes for the health and the environment. On the other side, Ni particles can have potential applications in the developing of magnetorheological fluids currently being used to improve the performance of mechanical devices. The present study raises the treatment of a residual effluent from a chemical nickel industry by applying a chemical precipitation which uses sodium hypophosphite as a reducer, and varying the order of the reagents involved in the conditioning of the reaction with respect to the reducer. The recovered solids were studied using different material characterization techniques to recognize the chemical composition (X-Ray Fluorescence, Inductively Coupled Plasma Mass Spectrometry), crystallinity and morphology (X-Ray Diffraction, Scanning Electron Microscope), surface charge and size distribution (Dynamic Light Scattering). By the chemical reduction treatment it was possible to decrease the amount of nickel in the residual between 97.25% and 99.50%, obtaining Ni particles that were then tested to be used in magnetic fluids. To this purpose a suspension was prepared by mixing the Ni particles with silicone oil in a constant solid/liquid ratio, and the rheological behavior of this suspension was evaluated as a function of the magnetic field and the deformation applied, revealing an interesting magnetorheological behavior.