Fine treatment of industrial sludges by high gradient magnetic separation

High gradient magnetic separation for the treatment of industrial waste sludges was tested on several synthetic slurries. These sludges were made up of chemical reagents of α-Fe2O3, Cr(OH)3and SiO2, which are weakly magnetic with the particle size less than about 20μm. These samples were prepared in slurry and tested individually and in mixture using a cyclic SALA-HGMS® 10-15-20 separator. In this report the change of magnetic capture through one cycle of separation was defined as a "magnetic capture process". Some experimental data were obtained in terms of the magnetic capture process. This process includes initial magnetic capture, build-up and breakthrough phenomena. Separation tests of paramagnetic or weakly magnetic α-Fe2O3from a diamagnetic SiO2were successful with the separation efficiency of more than 90 percent. Some theoretical approaches of the experimental data were conducted by using the particle trajectory model. The results show that the experimental data of the initial magnetic capture of α-Fe2O3and Cr(OH)3could be predicted appropriately by this model.