Phytomining of scandium using <i>Chrysopogon zizanioides</i> in red mud with addition of domestic sludge

Abstract Red mud is an industrial waste generated from the alumina production process which has increased every year. This waste is hazardous because it has a high pH and contains heavy metals, one of which is scandium (Sc). Scandium is a rare metal that is widely used in various industries, so it has a high economic value. Phytomining is an innovative technology that utilizes plants to extract metals from contaminated soil or waste. This research aims to determine the ability of Chrysopogon zizanioides plants to absorb scandium from red mud using domestic sludge as a planting medium and to investigate the effect of pH on scandium uptake. The research was conducted using an experimental method with a completely randomized design. The results showed that Chrysopogon zizanioides were able to absorb scandium from red mud, with the highest absorption occurring in the roots. The addition of domestic sludge as a planting medium can increase the availability of nutrients in the soil, help improve soil structure, and can lower the pH value from 10.85 on day 0 to 10.19 on day 28. Furthermore, this study found that decreasing the pH of the red mud can significantly increase the amount of scandium uptake by the plants with the total uptake value 7.7 mg/kg on day 28. This indicates that pH plays a crucial role in the bioavailability of scandium in red mud.