Copper waste processing under the combustion mode

In the work the possibility of processing of copper waste of wiring industry (Iran) under the combustion mode and preparation of copper powder have been studied. The copper waste used in this study represents mainly copper (I) oxide with small amount of metallic copper and having plate-like form of particles with linear size up to 2.5 mm (0.4-1.0 mm - 70 wt.%). Earlier the possibility of copper (II) oxide reduction under the combustion mode has been shown by using polystyrene (PS) as well as other organic compounds as reducer [1]. The same approach was used in [2] for preparation of copper powder from the mixtures of CuO/Cu2O and CuO/Cu. It should be emphasized that because of low exothermicity of Cu2OPS reaction, the reduction of pure copper (I) oxide by polystyrene in combustion mode is impossible (maximum value of Tad=460oC at PS/Cu2O=0.05-0.06). By this reason combustion limit exist for CuO-Cu2O-PS system at 40 wt.% content of Cu2O [2]. For increasing the exothermic effect of Cu2O-PS reaction and reduction of copper waste (hereinafter Cu2O) to metallic Cu in combustion mode the reactions thermal coupling approach was applied [3]. Namely, the weakly exothermic (Cu2O-PS) reaction was coupled with high exothermic NH4NO3-PS (hereinafter Nt-PS) one. Determination of optimal conditions of the process was based on the results of preliminary thermodynamic calculations for the above-mentioned system. The experiments were performed with the initial mixtures (Cu2O+0.06PS)+x(Nt+0.06PS).The burned samples were examined by XRD analysis and sieve analysis. According to XRD analysis results, at x> 0.2 complete reduction of copper takes place. The results obtained showed the possibility of using polystyrene with high caloric (Nt-PS) mixture for reducing copper waste to metallic copper under the combustion mode. Optimumconditions for obtaining powdered copper with certain microstructure were found out.