Optimization of Plant Species and Chelating Agents in Phytoextraction of Gold from Small-Scale Gold Mine Tailings

摘要

The disposal of small-scale gold mine tailings into agricultural land has caused a decline in crop production in the District of Sekotong, Lombok Regency of Indonesia. One of the technologies that can be developed for remediation of soil contaminated by small-scale gold mine tailings is phytoextraction. This study was conducted in two steps. The first step was aimed to study the effect of various doses of fertilizer and soil amendment on the production of biomass of two plant species studied previously, i.e. Paspalum conjugatum and Cyperus kyllingia. Each seedling of the two plant species was grown for 9 weeks on the tailing disposal dam in a 1 × 1 m plot. Treatments tested were (1) plant species (two species), and (2) dose of NPK fertilizer (50, 100, and 150 kg/ha), and (3) dose of organic matter (5, 10, and 15 t/ha). The second step was to study the effect of the type and dose of chelating agents on the best plant species resulted from the first step of this study. The treatments tested consisted of three types of chelating agent (ammonium thiosulphate, sodium thiosulphate and sodium cyanide) and three doses of each chelating agent (1, 1.5, 2 g/kg). At the time of harvest (9 weeks), shoot and root of each plant were separated for the analysis of Au accumulation. The results showed that type of plant, dose of organic matter, and optimal applied fertilizer that generated the highest growth and biomass production of the accumulator plants was a combination of P. conjugatum, 10 kg NPK fertilizer/ha, and 10 t organic matter/ha. The type and dose of chelating agents applied to the combined treatment affected Au accumulation. The best combination of type and dose of chelating agent was 2 g of ammonium thiosulphate /ha. Overall, the combination of plant species, fertilizer dose, organic matter dose, type of chelating agent, and dose of chelating agent was P. conjugatum with 100 kg NPK fertilizer/ha, 10 t organic matter/ha and 2 g ammonium thiosulphate/kg.