Effectiveness of mossy tin filters to remove mercury from aqueous solutionby Hg(0) reduction and Hg(0) amalgamation

Reduction of bivalent mercury (Hg(II)) by mossy tin combined with Hg(0) air stripping has been recently proposed as a method to remove Hg from groundw ater. We investigated the effectiveness of mossy tin to remove Hg(II) from aqueous solution at different flow rates and determined the retention of Hg through the formation of HgSn amalgams Results show that mossy tin layers of only 2 cm thickness can reduce 100% of 800 mu g Hg(II) l(-1) at a how ra te of about 1 Volume of drainable porosity min(-1) (Vol min(-1)), and even 100% of 5000 mu g 1(-1) at 0.125 Vol min(-1), 89% and 97% of the Hg(0) were retained in the filter through amalgamation. No Hg was remobilized from th e loaded tin filters by chloride (10-50 mg Cl- I-1) or dissolved organic ca rbon DOC (0.5-6 mg DOC l(-1)). The capacity of mossy tin to adsorb Hg was f ound to be at least 5-6% of the weight of the filter. The study shows that mossy tin has a high capacity to remove Hg effectively from aqueous solutio n. Disadvantages arise from the release of tin from the filters exceeding l egal limits of 20 mu g 1(-1) in most cases but occurred as mostly insoluble tin particles or Sn hydroxide. (C) 2000 Elsevier Science Ltd. All rights r eserved.