Effects of Na2O additions to copper slag on iron recovery and the generation of ceramics from the non-magnetic residue

Abstract

A novel process is proposed in this paper for a green and efficient utilization of copper slag. The basic premise involved the addition of different amounts of Na2O into molten copper slag and evaluation of the effects on the magnetic fraction and the properties of ceramics generated from the non-magnetic residue, and mechanisms of the effects were further studied by XRD, SEM, EDS, viscosity test, hysteresis loop and FTIR. The results showed that Na2O additions dropped the viscosity of the slag markedly, which promoted the growth of magnetite, but decrease quantity of magnetite due to oxidization of Fe2+ and precipitation of crystals containing Fe3+. With the addition of 4 % Na2O, solidification temperature of slag decreased from 1790 K to 1530 K, optimum iron recovery rate of 81.08 % was achieved. Na2O as flux in ceramics obviously reduced its sintering temperature and meantime decreased its bending strength because of insufficient crystallization of its main minerals. The non-magnetic residue from magnetic separation of slag with addition of 4% Na2O was converted into ceramics with a much low sintering temperature of 1268 K (995 °C) and qualified bending strength of 64.5 MPa.