Production of metallic nanoparticles, from industrial residues, by the use of different types of reduction gases

Abstract

The need to enhance and reuse existing materials on secondary sources of metals has had quite an impact in recent times. Several processes and technologies had being studied for recovery of raw materials from industrial waste generated. This study focuses on the possibility of waste reducing, from the galvanic floor covering industry, with the aim of obtaining micro or nano-particles of nickel or a nickel based alloy. Sludges from one galvanic treatment plant were used as base material in two conditions: as produced and after a hydrometallurgical treatment for metal concentration. Several reducing agents were used in this study: a synthesis gas from a polymer pyrolysis and solid polymer agents (PVC, HDPE and PP residues). Obtained products were characterised in terms of metallic particles production during the reduction treatment and by SEM/EDS analysis on the final products. A simultaneous differential thermal and thermogravimetric equipment (DSC/TGA) was used for the study of the reduction process with a reduction gas obtained from the pyrolysis of chlorine free PVC derived char. The obtained results show that it is possible to obtain small metallic particles, in the range of 60 to 240 nm, at 800 ºC. Reduction tests, by the use of a solid residue, were made in a laboratorial furnace with two independent heating zones. Best results were obtained with de-chlorinated PVC as a reduction agent with the production of metallic particles, in the range of 150 to 600 nm, at 800 ºC. For all the tested conditions the metallic particles were constituted by Ni and Cu with variable chemical composition.