Recovery Ion Hg2+ dari Limbah Cair Industri Penambangan Emas Rakyat dengan Metode Presipitasi Sulfida dan Hidroksida

Abstract

Unlicensed gold mining activities (PETI) using mercury (Hg) as a gold element binder is called the amalgamation process. Mercury is a heavy metal toxic. The use of mercury can potentially cause pollution in environment, especially the aquatic environment. For overcoming the heavy metals mercury in liquid waste, it needs an alternative wastewater treatment method called chemical precipitation. This study is aimed to recover Hg2+ ions from liquid wastes by using sulphide precipitation and hydroxide methods. This research studied the effect of pH on Hg ions which is deposited in the precipitation process and found out the rate of Hg precipitation formation. Precipitation was done by using sodium sulphide (Na2S) 0.3 M and Ca(OH)2 0.004 M as a precipitation agent with rapid mixing speed for about 200 rpm for 3 minutes and continued with slow mixing for about 40 rpm for 30 minutes. Then, just let the liquid sample be for 24 hours to precipate the precipitate formed. The results show that precipitation method by using a Na2S solution can decrease the content of Hg in HgCl2 synthetic waste. An optimum mass of HgS precipitate of 0,0458 g was achieved pH 9 for 200 mL of wastewater liquid with a removal efficiency percentage up to 99.81%. The concentration of mercury can be derived from 130 ppm to 0.25 ppm. The rate of formation of HgS precipitate was obtained 0.0004g/ hour. While, hydroxide precipitation method can decrease mercury level up to 90,11% at pH 12 and mass of Hg (OH)2 precipitate obtained is 0,2784 g. However, the result of EDX analysis of the precipitate of Hg (OH)2 shows that the content of Hg precipitate is just 0.281%.