Stabilization/solidification of mercury contaminated soil of traditional gold mining in Kulon Progo Yogyakarta, Indonesia using a mixture of Portland cement and tras soil

Traditional gold mining activity is one of the source of mercury contamination. Total mercury concentration around the tailing ponds in Kulon Progo ranged from 0.30 to 22.51 mg/kg, which the exceeded the quality standard values set by the government of Indonesia No. 101 of 2014 which is 0.3 mg/kg. One method that can be applied is stabilization/solidification (S/S). This study aims to determine the optimum composition of Portland cement and tras soil used in S/S with contaminated soil. The study at first step, Portland cement and tras soil compositions was used by variations of the weight value of 100: 0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90. At second step, contaminated-soil samples were added into optimum from first step, with a variation composition of binder: soil iare 50:50, 40:60, 30:70, 20:80, and 10:90. Toxicity Characteristic Leaching Procedure was applied based on US EPA method 1311. First test result in optimum composition of Portland cement: tras soil (10:90), with the compressive test value of 96 kg/cm2. The second result of compressive test values of binder: contaminated soil (10:90) was 6 kg/cm2 is with mercury concentrations in the TCLP test of 0.0011 mg/L. The result of compressive test met the quality standards of US EPA for the management of contaminated soil at 3.5 kg/cm2. The result of TCLP test met the quality standards for products of S/S in accordance with Government Regulation 101 Year 2014 at 0.05 mg/L.