Determination of Total Mercury and Mercury Thermospecies in Cement and Cement Raw Materials

Cement manufacturing is the second largest anthropogenic source of Hg emissions in the environment. Therefore, the establishment of analytical methodologies that can be utilized in the determination of Hg concentration from cement raw materials and cement is of great importance. The total Hg and Hg thermospecies in cement raw materials and cements were determined by thermal desorption techniques with a Zeeman Hg analyzer. No chemical pre-treatment of samples is required for this technique prior to analysis. An optimum single-stage temperature program was applied to determine total Hg at an optimum heating rate of approximately 5 °C s−1 while Hg thermospecies were determined over four stages at an optimum heating rate of approximately 0.2 °C s−1 per stage from ambient temperature to 720 °C. Total mercury concentrations in cement raw materials ranged between 2.19 ng g−1 and 395 ng g−1, while in cement, concentrations ranged between 1.32 ng g−1 and 31.0 ng g−1. The highest Hg contents were found in dust return (580 ng g−1 and 679 ng g−1). Hg thermospecies determination showed that cement raw materials and cements contain one Hg thermospecies that is released at 20–180 °C while dust return contained one to four Hg thermospecies that could be released at 20–180 °C, 180–360 °C, 360–540 °C, and/or 540–720 °C, thus indicating that new Hg compounds are formed during cement production.