Development of a hydrometallurgical process for the recovery of pure alumina from black dross and synthesis of magnesium spinel

In order to recover pure alumina and synthesize magnesium spinel from black dross, a hydrometallurgical process was developed. This process consisted of 1) NaOH leaching of the mechanically activated black dross, 2) removal of silicate(IV) from the leaching solution by adsorption followed by coagulation, 3) precipitation of aluminum hydroxide from the purified leaching solution, 4) synthesis of magnesium spinel. Continuous experiments on the above-mentioned steps at optimum conditions were performed. Magnesium spinel was synthesized at 1000 °C for 5 hs by the co-precipitation method. The purity of spinel was 99.99 % and its characteristics were analyzed by XRD and SEM. Mass balance of the whole process indicated that the recovery percentage of alumina from the black dross was only 34 % owing to low leaching percentage. Further work on the pretreatments of black dross to improve its dissolution behavior is needed.