Environmental exposure and flux of thallium by industrial activities utilizing thallium-bearing pyrite

Abstract

Thallium (Tl) is a typical toxic heavy metal, with higher toxicity to mammals than Hg, Cd, and Pb. Accurate assessments of its environmental exposure and flux are central to effective management and control of Tl pollution. This paper first presents in detail the environmental exposure and flux of Tl by typical industrial activities utilizing Tl-bearing pyrite minerals to produce sulfuric acid. For this purpose, sequential extraction and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were used to investigate total content and geo-chemical partitioning of Tl in raw pyrite ores and solid roasting wastes, thereby uncovering Tl distribution and transformation during the production process. Results showed that some portions of Tl bearing in the minerals went into vapor, which transferred Tl into different processes; and some portions of Tl went into water during the gas washing procedure, leaving some other portions remained in the solid slags. More importantly, detailed investigation revealed that 40% of Tl in the pyrite minerals was active, among which 25% of Tl originally in the pyrite minerals was washed into water during gas cleaning process and 15% of active Tl retained in the slags. The latter portion of active Tl could be possibly transferred to the soil or water with the slag deposal or being reused; and 60% of Tl remained relatively stable in the residual phase.