Study on mechanisms of different sulfuric acid leaching technologies of chromite

Abstract

The extraction of chromate from chromite via the sulfuric acid leaching process has strong potential for practical use because it is a simple and environmentally friendly process. This paper aims to study the sulfuric acid leaching process using chromite as a raw material via either microwave irradiation or in the presence of an oxidizing agent. The results show that the main phases in Pakistan chromite are ferrichromspinel, chrompicotite, hortonolite, and silicate embedded around the spinel phases. Compared with the process with an oxidizing agent, the process involving microwaves has a higher leaching efficiency. When the mass fraction of sulfuric acid was 80% and the leaching time was 20 min, the efficiency could exceed 85%. In addition, the mechanisms of these two technologies fundamentally differ. When the leaching was processed in the presence of an oxidizing agent, the silicate was leached first and then expanded. By contrast, in the case of leaching under microwave irradiation, the chromite was dissolved layer by layer and numerous cracks appeared at the particle surface because of thermal shock. In addition, the silicate phase shrunk instead of expanding.

Keywords

chromite / leaching mechanisms / microwave leaching / sulfuric acid / microanalysis

References

[1] Zhang S.L., Zhang H.Z., Wang Z.L., Wang X.Z., Wang H.M. Research progress of cleaner production technology of chromate. Inorg. Chem. Ind., 2014, 46(2): 6.

[2] Jiang M.F., Zhao Q., Liu C.J., Shi P.Y., Zhang B., Yang D.P., Saxén H., Zevenhoven R. Sulfuric acid leaching of South African chromite. Part 2: optimization of leaching conditions. Int. J. Miner. Process., 2014, 130(10): 102.

[3] Li Z.Y. The current status and development suggestion of chromates industry. Inorg. Chem. Ind., 2006, 38(4): 1.

[4] Shi P.Y., Liu S.L. Experimental study on sulphur acid leaching of chromite. J. Chin. Rare Earth Soc., 2002, 20, 472.

[5] Ji Z. Development status of China’s chromates in recent 50 years. Inorg. Chem. Ind., 2010, 42(12): 1.

[6] Zhao Q., Liu C.J., Shi P.Y., Zhang B., Jiang M.F., Zhang Q.S., Zevenhoven R., Saxén H. Sulfuric acid leaching kinetics of South African chromite. Int. J. Miner. Metall. Mater., 2015, 22(3): 233.

[7] Ji Z. Present development situation for new technologies of sodium chromate in China: I. Inorg. Chem. Ind., 2014, 46(12): 1.

[8] Yang D.J., Wang S.N., Chen X.F., Zheng S.L., Li S.H. Removing vanadium from sodium chromate neutral liquid by non-calcium roasting technology with chromium salt. Chin. J. Nonferrous Met., 2014, 24(1): 279.

[9] Zhang Y., Zheng S.L., Xu H.B., Du H., Zhang Y. Phase equilibria in the NaOH–Na₂CrO₄–Na₂CO₃–H2O system. J. Chem. Eng. Data, 2010, 55(7): 2542.

[10] Yianatos J.B., Bergh L.G., Díaz F., Rodríguez J. Mixing characteristics of industrial flotation equipment. Chem. Eng. Sci., 2005, 60(8-9): 2273.

[11] Jafarifar D., Daryanavard M.R., Sheibani S. Ultra fast microwave assisted leaching for recovery of platinum from spent catalyst. Hydrometallurgy, 2005, 78(3-4): 166.

[12] Begum Z.A., Rahman I.M.M., Tate Y., Sawai H., Maki T., Hasegawa H. Remediation of toxic metal contaminated soil by washing with biodegradable aminopolycarboxylate chelants. Chemosphere, 2012, 87(10): 1161.

[13] Fedje K.K., Yillin L., Strömvall A.M. Remediation of metal polluted hotspot areas through enhanced soil washing-Evaluation of leaching methods. J. Environ. Manage., 2013, 128, 489.

[14] Huang J.H., Rowson N.A. Hydrometallurgical decomposition of pyrite and marcasite in a microwave field. Hydrometallurgy, 2002, 64(3): 169.

[15] Huang J.H., Rowson N.A. An application of microwave pre-oxidation in improving gold recovery of a refractory gold ore. Rare Met., 2000, 19(3): 161.

[16] Huang J.H., Rowson N.A. Heating characteristics and decomposition of pyrite and marcasite in a microwave field. Miner. Eng., 2001, 14(9): 1113.