Pengolahan Tailing Sianidasi Bijih Emas dengan Proses Oksidasi-Presipitasi

The alternative gold ore processing in small-scale gold mining to replace the amalgamation process is cyanidation. Both processes harm the environment, however, cyanidation is relatively easier to control. In addition, obtaining gold by cyanidation is higher than amalgamation increase the economic value even though the process is more complex than amalgamation. Cyanidation produces tailing containing cyanide and heavy metals, the concentration of which is highly dependent on the composition of the ore and the conditions of the cyanidation process. The effort to treat cyanidated tailing by the oxidation-precipitation process using SO2 sourced from Na2S2O5, O2 from the air, and Cu(II) as a catalyst was carried out to reduce the concentration of cyanide and dissolved heavy metals in tailing. The trial stages of the oxidation-precipitation process carried out are determining the process parameters on a one-liter scale and followed by testing the application of process parameters on 20 liters scale. The process parameters for the oxidation-precipitation of cyanide and heavy metals in tailing were determined sequentially, that: catalyst concentration Cu(II), initial pH, time, and Na2S2O5/CN- weight ratio. The Application test of process parameters at a catalyst concentration of Cu(II) 50 mg/L, initial pH 9, the processing time of 5 hours, and the ratio by weight of Na2S2O5/CN-75 was able to reduce the concentration of free cyanide, WAD cyanide, and total cyanide in both the liquid and solid phases of tailing significantly. The oxidation-precipitation process parameters were also able to reduce the concentration of dissolved heavy metals in the liquid phase of tailing with various decreasing values. The quality of the liquid phase of tailing for the concentration of cyanide ion and the total concentration of dissolved heavy metals such as Cu, Zn, and Pb treated by the oxidation-precipitation process has been able to meet the specified quality standard values.