Recovery of magnetite from waste ferrous sulfate using polyethylene glycol (PEG) as a dispersant

The effect of PEG dispersant on the magnetic separation of magnetite (Fe₃O₄) synthesized from ferrous sulfate solution via co-precipitation method with calcium hydroxide as the precipitant was investigated. The results indicated that a PEG dispersant could significantly affect Fe₃O₄ recovery. Adding PEG during the preparation of Fe₃O₄ was unfavorable for Fe₃O₄ recovery. When the PEG-6000 concentration was increased from 0 to 8 g/L, the iron grade and median particle size of the Fe₃O₄ product decreased from 65.58% and 2.35 μm to 57.79% and 1.35 μm, respectively. However, adding PEG during the wet milling of the mixed product promoted the subsequent recovery of Fe₃O₄. When the amount of PEG-200 increased from 0% to 4% of the powder mass, the grade of iron in the Fe₃O₄ product increased from 65.58% to 68.32%. While the relative molecular mass of PEG at an amount of 4% of the powder mass increased from 200 to 20000, the grade of iron was reduced from 68.32% to 66.70%.