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

The rate of gaseous Hg0 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 Hg0 was oxidized by CuS to HgS on natural sphalerite after Cu2+ activation. In a similar intrinsic ZnS pathway, physically adsorbed Hg0 was oxidized by ZnS to HgS. The rate of the CuS pathway for Hg0 capture was generally significantly larger than that of the intrinsic ZnS pathway. Thus, Hg0 adsorption onto natural sphalerite was notably accelerated after Cu2+ activation. However, the kinetic analysis indicated that the capacity of natural sphalerite for Hg0 capture did not vary. Because the properties of the activated sphalerite for Zn smelting were barely degraded after Hg0 capture, the spent activated sphalerite for Hg0 capture can be reused for Zn smelting. Moreover, most of the gaseous Hg0 captured by activated sphalerite can be recovered eventually as liquid Hg0 in the condenser unit of Zn smelters. Thus, Hg0 recovery by activated sphalerite is a cost-effective and environmentally friendly technology to recover Hg0 from Zn smelting flue gas, thus replacing the complex and dangerous Boliden-Norzink process.