Rice Husk as A Versatile Biosorbent: A Systematic Review of Wastewater Treatment Applications

Rice husks, an abundant agricultural waste product, have emerged as a versatile and sustainable biosorbent for wastewater treatment applications. This systematic review comprehensively examined the effectiveness of rice husks and their derivatives in removing a wide range of pollutants, including heavy metals, organic compounds, inorganic anions, and emerging contaminants. Various modification strategies, such as chemical activation, thermal treatment, and nanostructuring, have enhanced the adsorption capacity and selectivity of rice husk adsorbents. This review highlights the potential of rice husks in addressing specific wastewater challenges, including BOD and COD reduction in dairy effluents, casein recovery, and nutrient removal. The adsorption process is influenced by several factors, such as pH, adsorbent dosage, contact time, and temperature, and conforms to well-established isotherm and kinetic models. Rice husk-based materials have demonstrated high removal efficiencies for heavy metals (e.g., Zn, Pb, Cu, and Ni), organic pollutants (e.g., phenols, dyes, and surfactants), and nutrients (e.g., ammonium and phosphate). Furthermore, the eco-friendly nature and cost-effectiveness of rice husks position them as sustainable alternatives to conventional adsorbents, aligning with the principles of a circular economy. However, despite significant progress has been made, further research is required to optimize modification techniques, explore new applications, and scale up these technologies for industrial use. This review underscores the promising role of rice husks in advancing sustainable wastewater treatment and resource recovery.