Enhanced removal of organic matter from oxygen-pressure leaching solution by modified anode slime

Abstract

Organic matter has become a typical harmful impurity, posing a serious problem and catastrophic effects in the hydrometallurgical extraction of zinc. The highly efficient and inexpensive method for the removal of organics from the leaching solution is of great practical significance for the efficient operation of zinc hydrometallurgy. For this reason, the removal of organic matter from oxygen-pressure leaching solution using modified anode slime was investigated by TOC analysis, FTIR spectroscopy, XRD, GCMS, and other characterization methods, and its mechanism was also discussed. The results show that the removal of organic matter using anode slime modified with sulfuric acid was significantly improved, and the removal of TOC reached 57.83% for anode slime modified at a temperature of 80 °C with a ratio of sulfuric acid to anode slime of 14 mL/100 g, which was more than 2.7 times that of untreated anode slime. The good removal effect of organic matter using the modified anode slime could be attributed to the transformation of inert α-MnO2 to active MnOOH by concentrated sulfuric acid-mediated modification. It was also found that the acid–solid ratio and temperature exhibited a significant effect on the modification of anode slime. The XPS analysis results of Mn 2p, Mn 3s, and O 1s, combined with the XRD patterns of the modified products indicated that the modification of anode slime led to the conversion of MnO2 in anode slime to MnOOH in the presence of H2SO4. However, MnO2 was further converted into high crystallinity MnOOH, even MnSO4 when the temperature exceeded 80 °C or the acid–solid ratio exceeded 18 mL/100 g, resulting in the decreased degradation performance for organic matter. The characterization results of FTIR spectroscopy and GCMS show that modified anode slime does not exhibit a degradation effect on all types of organic substances in leaching solution; however, it is very effective for some alcohols, olefins, and esters.