The potential of imperata cylindrica for phytomining and soil remediation of red mud waste

As industrialization accelerates, the demand for metals, particularly aluminium, continues to rise. This growth has also led to an increase in by-products from the bauxite ore refining process, namely red mud. The highly alkaline nature of red mud, combined with its heavy metal content, poses significant environmental challenges. However, red mud also contains rare earth elements (REEs) that can serve as valuable secondary resources. An environmentally friendly approach to recovering these metals is phytomining, which utilizes plants and simultaneously contributes to land remediation. This study aims to evaluate the potential of Imperata cylindrica in metal recovery and the remediation of red mud waste. The research began by conditioning the pH of red mud through the addition of citric acid, fertilizers, and by adjusting the red mud composition to levels of 40% based on the optimum result using Response Surface Methodology. Phytomining was initiated once the pH of the substrate (a mixture of red mud and soil) reached an optimal range of 8.0–8.5. The results demonstrated that Imperata cylindrica was capable of absorbing several rare earth metals, including gadolinium (Gd), neodymium (Nd), and cerium (Ce), with concentrations of 119.5 mg/kg, 16.5 mg/kg, and 6.67 mg/kg, respectively, in its roots. Additionally, the plant showed the ability to absorb major components such as iron (Fe) and titanium (Ti), with the metals distributed throughout the plant's roots, stems, and leaves.