Removal of Mercury from Aqueous Solutions with Calcium Silicon

Abstract

Calcium silicon proved to be very effective in removing mercury from aqueous solutions of 0.1 to 10000 ppm Hg.
The mercury removal rate increased with decreasing particle size of calcium silicon, and calcium silicon particles of 250 to 590, μm in diameter yielded the best results. The removal of mercury was conducted satisfactorily in acid solutions, but it is recommended to adjust the pH of the solutions at about 4 to prevent the consumption of calcium silicon by acid.
Hg²⁺ ion in the solutions was reduced chiefly by the calcium moiety to Hg²⁺ ion and Hg which precipitated from the solutions. A part of the Hg volatilized into the air. The volatilization fraction of Hg decreased with increasing mercury concentration and amount of calcium silicon.
The removal of mercury was also affected by other factors than reduction with calcium silicon. The maximum mercury removal capacity of calcium silicon was as large as 40 m-atom Hg/g calcium silicon, which was much larger than theoretical values calculated from the amount of dissolution of calcium and silicon. Residual mercury concentrations were found to be lower than the solubilities of the reaction products.
When a calcium silicon packed column was used, the problem of clogging of column due to disintegration of calcium silicon was noticed.