Efficient removal of manganese (II) ions from aqueous solution using biosorbent derived from rice husk

Abstract

Rice husk (RH), an abundant agricultural byproduct, presents significant environmental concerns due to its accumulation and potential leaching of hazardous manganese (Mn) ions. This study evaluates the feasibility of using rice husk as an eco-friendly and cost-effective biosorbent for removing Mn(II) from contaminated water. A modified adsorbent, nitric acid-functionalized rice husk (NT-RH) was synthesized and characterized using SEM-EDX, PXRD, and FTIR techniques to assess its structural properties. The NT-RH exhibited a porous, macro-structured network that enhanced its adsorption capacity. Batch experiments examined key Mn(II) removal variables, including adsorbent dosage, temperature, contact time, and pH. The results demonstrated a maximum removal efficiency of Mn(II) of 94.96 % under optimal conditions, which included a manganese concentration of 50 ppm, an adsorbent mass of 0.6 g, a temperature of 25°C, a pH of 7, and a contact time of 60 minutes. The adsorption process was spontaneous and exothermic, with kinetics described by a pseudo-second-order model and isotherms best represented by the Freundlich model. Therefore, this research highlights the potential of rice husk as a sustainable material for removing Mn(II), effectively addressing the dual challenges of agricultural waste management and water purification. In addition, the development of NT-RH represents a promising method for enhancing biosorbent materials within environmental management, materials science, and sustainable wastewater treatment technologies.