Rice Husk-Based Adsorbents for Removal of Metals from Aqueous Solutions

Adsorption is one of the main methods of water purification. Novel advanced, eco-friendly, cost-effective adsorbents with high adsorption capacity and selectivity are required to remove pollutants from aqueous solutions. Plant polymers are viewed as both prospective adsorbents and as raw materials to produce them instead of conventional adsorption materials. There is widespread interest in using rice husk as a universal sorbent to remove different contaminants from aqueous media because of its surplus availability, low cost, and high content of oxygen containing functional and silanol groups as active sites for adsorptive extraction. Different methods of heat and chemical treatments have been developed to improve the sorption properties of raw rice husk. Unmodified rice husk and rice-husk-based sorbents have been tested to uptake non-ferrous, ferrous, minor, precious, rare, and rare-earth metals and radionuclides from artificial and industrial solutions, natural contaminated water, and industrial wastewater. This review summarizes the results of numerous studies and characterizes the current state of work in this area, with recommendations for further development.

Automated summary

Adsorption is an important method for water purification, and the development of new, advanced, environmentally friendly, and cost-effective adsorbents with high adsorption capacity and selectivity is necessary. Plant polymers are considered promising adsorbents and can be used as raw materials for the production of adsorption materials. Rice husk is widely used as a universal sorbent due to its abundant availability, low cost, and high content of oxygen-containing functional and silanol groups. Various heat and chemical treatments have been developed to enhance the adsorption properties of rice husk.