Treatment technology for jewelry wastes

Residues of jewelry are of different types depending from the cycle of production utilised. Precision casting residues disposal is a very influential problem; as a matter of fact, this process is carried out from a lot of firms. The aim of the present experimental work was devoted to investigate alternative process, for solid residues disposal (plaster-cast) coming from precision casting, with two scope: to dispose residues and to recover precious metals; in fact, gold recovery would involve the decrease of the costs for disposal of the residues. The investigation has been carried out at laboratory scale, on samples collected from selected firms from main goldsmith areas: precision casting residues were submitted to treatment operations including gold recovery section. By X-Ray Diffraction Spectrometry it was determined that main components were anhydrite (CuSO4), quartz and cristobalite (SiO2). Quantitative chemical analyses have been conducted by plasma-mass spectrometer: the content of toxic-metals was determined; average of gold content was of 2.5 g/t Au. Finally a technical feasibility study has been carried out to perform low environmental impact process and a flow-sheet for gold recovery has been designed.