Treatment of tannery wastewater by silica nanoparticles produced from rice husk ash via a green route.

Rice husk, which is one of the abundant agricultural biomasses in nature, contains organic and inorganic elements, spastically silica. This waste is frequently managed via incineration, resulting in the contamination of soil, water, and air due to emission of greenhouse gasses and ash. In the present investigation, the potential of silica powder obtained from the rice husk was demonstrated by the removal of Cr(III) from the tannery wastewater. Different combinations of sulfuric, hydrochloric, and acetic acids were used as precipitation agents to produce silica through the conventional and ultrasound-assisted techniques. The mesoporous silica fabricated via the sonication indicated the larger pores, 22 nm, compared to that produced via the conventional method by the employment of sulfuric acid, 10 nm, leading to achieve an adsorption capacity ~385 mg g. Although both of applied techniques could develop mesoporous structure, precipitation should be carried out under sonication in the presence of acetic acid for the green production of silica with the appropriate adsorption performance. The conversion of rice husk into silica powder with specific surface area ~62 m g could prevent the environmental pollution due to employment of acetic acid in the precipitation stage.