Removal of Mercury from Laboratory Wastewater by Iron Powder

Abstract

The removal of mercury from laboratory wastewater is very difficult, because it frequently contains various substances which stabilize Hg²⁺ as Hg(II) complexes. In this paper, the removal of mercury from wastewater containing some ligands has been *studied by a Fepowder method. The apparatus used is shown in Fig.1. The effluent from a Fe-column was aerated and both the volatilized mercury (Hg⁰) and the residual mercury after aeration were measured. The maximum recovery of mercury was obtained at pH 2, but a large amount of Hg⁰ was detected in the solution passed through the column in the range of pH 1 to 6(Fig.4). In the absence of ligands, 100 mg/l of Hg²⁺ in the influent was reduced to 33 μgl by the Fe-column treatment and the subsequent aeration. When the effluent from the column was aerated at pH 8, the residual mercury concentration in the filtrate was reduced to 4.4μgl (Fig.7). Even in the presence of any ligand used in our laboratory (Table 1), the recovery of mercury was over 93%, but in the case of some ligands, the residual mercury concentration in the solution after aeration at pH 2 was over the effluent standard value (Table 2). However, the residual mercury concentration in the filtrate was reduced to less than 2 μgl by aeration at pH 8 except for the case of KI or peptone (Table 2). These results led us to the conclusions that the Fe-column can efficiently recover the mercury contained in laboratory wastewater and that a large portion of the mercury remained in the effluent from the column can be removed by the aeration and precipitation at pH 8.