New residue-free processing of copper slag from smelter

Deposited copper slag originated from a region Mansfeld (Saxony-Anhalt, Germany) was characterized from mineralogical, chemical and structural point of view for purpose of its sustained processing and removal. Subsequently hydrometallurgical processing of copper slag was investigated because of extraction of metals as Zn, Cu, Ni, Co, Mo, Cr, V and Fe in total content about 5%. Although the slags with their mineralogical composition of calcium, magnesium, aluminum, and iron silicates are perfectly suitable as building materials, their cumulative heavy metal content prevents this. Novel residue-free recycling process for copper smelter slag was developed which consists of sorting, roasting, leaching with HCl, carbonate precipitation, precipitate complexation and solvent extraction of metals steps. This process solves the problem with calcium silicate matrix which enclosed dissolved metals. By setting pH of leaching process to ∼2.5, 80-90% of Cu can be extracted and dissolution of silicate matrix can be prevented. Mass balance of process strategy indicates the proceeds from four marketable products: blasting agent, cement additive, metal salts solution, and fertilizer, which make the process more economical with sustainable benefits. Economic evaluation of new process is also done and confirmed its utility and favourable balance.