けん気的に安定化した汚泥からの水銀の抽出

Abstract

Mercury extraction was carried out using an anaerobically stabilized sludge originated from our laboratory wastewater treatment plant. Mercury in the sludge was not directly extracted not only with KI, KBr, Na2S2O3, ethylenediaminetetraacetate or cysteine solution at neutral pH, but also with 1.0 mol/l HCl. However, 20 per cent of mercury was extracted with 0.1 mol/l NaOH. On the other hand, 55 per cent of mercury was extracted with 0.1 mol/l KI at neutral pH when the anaerobic sludge was aerated for 6 days. Treatment of the aerated sludge with hydrogen peroxide solution, followed by treatment with KI solution, resulted in 85 per cent extraction of mercury. Most of mercury remaining in the sludge could be extracted by repeated treatment with KI solution. Mercury in the anaerobic sludge could also be extracted by aerating the sludge in 0.1 mol/l KI. Further more, when the anaerobic sludge was treated with Ca (OCl)2 at pH 8 and at pH lower than 2, 20 and 80 per cent of mercury were extracted. Other metal ions, such as Cu2+, Cd2+, Pb2+ and Zn2+, were scarcely extracted with 0.1 mol/l KI from the anaerobic sludge as well as aerobic or hydrogen peroxide treated sludges. From these results, it was clarified that KI was a specific chemical for the extraction of mercury in the sludge and that some oxidation process was essential for the effective extraction of mercury.