Removal of mercury from spent carbon sorbents

Waste active carbon (sampled from landfill sites A and B), 1.1 g, was treat ed (i) with 40 cc 0.11 M AcOH, shaked 12 h, and filtered; (ii) the solid re sidue was treated with 40 cc 0.1 M NH2OH . HCl at pH 2, shaked 12 h and fil tered; (iii) the solid residue was treated with 20 cc 8.8 M H2O2, heated tw ice to 358 K treated 2 h with 50 cc 1 M AcONH4 and filtered, and (IV) the s olid residue was microwave-mineralized in (a) HNO3 or (b) in aqua regia. St eps (i)-(iii) removed in total less Hg than 0.2% of the sorbent A or B weig ht; Hg is thud believed to occur as sparingly soluble compounds and HgS is thought to be absent. Medium b was the more efficient and allowed to remove up to 96% of total Hg (i.e., of 4.56% and 5.86% in A and B, resp., Table 1 ). Cementation of waste carbons A and B and their subsequent deposition on landfill sites is considered to be safe.