Cleaning Up Mercury Waste

Cleaning Up Mercury Waste

Author: Stuart Beardsworth

Mercury pollution threatens the environment and human health across the globe. Mercury is a highly toxic substance that has found uses in many places throughout industry, including coal mining, small-scale gold mining, some agricultural activities, and various metallurgic processes.

Justin M. Chalker, Flinders University, Bedford Park, Australia, and colleagues have developed a porous polymer as a low-cost sorbent for mercury. The team combined elemental sulfur and common cooking oils, including olive oil, canola oil, and sunflower oil. In the first step, sulfur was heated to 180 °C to initiate a ring-opening polymerization. Then, an equal mass of oil was added and stirred vigorously to ensure homogenous mixing. The process produces a polymer that ensures enough sulfur availability for mercury capture, while not being too brittle. The synthesis could be easily scaled to give 40 g of polymer. According to the researchers, larger, industrial-size batches should also be possible.

The mercury-capture properties of the sulfur/canola oil polymer were tested. In solution (2 g of polymer to 5 mL aqueous solution of HgCl2), on average, 90 % of the mercury was removed after 24 hours. In a test of pure liquid mercury, 1 g of the polymer could remove 99 % (99 of 100 mg) mercury, producing metacinnabar, a non-toxic, non-water-soluble form of mercury. Another common pollution problem is mercury waste within soil. For this, the polymer was shown to effectively remove mercury traces within 24 hours from mercury-treated soil samples. The polymer particles could be separated afterward by simple filtration.

Further studies were undertaken after preparing a more porous version of the polymer by synthesis in the presence of a sodium chloride porogen. This material was able to remove up to 67 % mercury from Hg-containing nitrogen flows. It was also effective (up to 81 %) in removing mercury bound to organic matter, as well as from aqueous solutions of organomercury fungicides. This shows promise for applications as a soil additive to prevent mercury leaching from agriculture into wastewater. Neither the polymer itself nor the mercury-bound polymer are toxic to human cells.


 

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