Acceleration of Hg0 Adsorption onto Natural Sphalerite by Cu2+ Activation during Flotation: Mechanism and Applications in Hg0 Recovery

Abstract

The rate of gaseous Hg-0 adsorption onto natural sphalerite increased by approximately 1.9-7.7 times after Cu2+ activation during flotation of the natural sphalerite to remove impurities. Via a new pathway involving CuS, physically adsorbed Hg-0 was oxidized by CuS to HgS on natural sphalerite after Cu2+ activation. In a similar intrinsic ZnS pathway, physically adsorbed Hg-0 was oxidized by ZnS to HgS. The rate of the CuS pathway for Hg-0 capture was generally significantly larger than that of the intrinsic ZnS pathway. Thus, Hg-0 adsorption onto natural sphalerite was notably accelerated after Cu2+ activation. However, the kinetic analysis indicated that the capacity of natural sphalerite for Hg-0 capture did not vary. Because the properties of the activated sphalerite for Zn smelting were barely degraded after Hg-0 capture, the spent activated sphalerite for Hg-0 capture can be reused for Zn smelting. Moreover, most of the gaseous Hg-0 captured by activated sphalerite can be recovered eventually as liquid Hg-0 in the condenser unit of Zn smelters. Thus, Hg-0 recovery by activated sphalerite is a cost-effective and environmentally friendly technology to recover Hg-0 from Zn smelting flue gas, thus replacing the complex and dangerous Boliden-Norzink process.