Morphological analysis of mercury in solid wastes from natural gas processing plants: optimization of a...

Determination of mercury species over solid waste from natural gas processing plants is a prerequisite for solid waste decontamination and mercury recycling. The temperature-programmed decomposition and desorption method (TPDD) is a promising technique to determine the mercury species over solid waste. Mercury species over solid wastes with complex components and similar desorption temperature, however, cannot always be determined using only the TPDD method. In the present study, the EPA 3200 method was applied to optimize the TPDD process for speciation of the mercury compound over solid wastes collected from a natural gas processing plant, including four spent adsorbents and three sludges. The mercury species with similar desorption temperatures over solid wastes were completely separated by the EPA 3200 method optimized TPDD process. The mercury species over spent adsorbents and sludges could be determined based on the fingerprints of the mercury compounds. The mercury compounds over spent adsorbents were specified to be Hg⁰ and/or M-Hg amalgam, HgS(black) and HgO(red), of which HgS(black) was the primary mercury compound. However, the mercury species over sludge were analyzed to be Hg⁰ and/or M-Hg amalgam, HgCl₂(minor), HgS(black), HgO(yellow) and HgS(red). The mercury recovery rates of solid wastes ranged from 73% to 120%. With the above results, it was considered that the EPA 3200 method optimized TPDD process was a promising method to specify and semi-quantify the mercury compounds in solid waste.