Utilization of secondary agricultural products for the preparation of value added silica materials and their important applications: a review

Abstract

Silica and its compounds are widely used in the industries like pharmaceutical, chemical, agricultural, and research sectors. Generally, silica is obtained from natural precursors available in the form of silicates. Extensive use of silica makes it necessary to find the new sources and methods of synthesis. Secondary agricultural products and by-products like rice husk, sugar cane bagasse, corn cabs, wheat straw, rice straw, grasses, and coconut husk contains considerable amount of silica. The methods for the extraction of silica includes burning of materials to make it ash, acid treatment, base treatment, ionic liquids, and sol-gel methods. Among all the methods, sol-gel is an important method of silica synthesis. Highly pure and desirable silica materials can be synthesized by the chemical leaching process, where metallic impurities can be removed by the acid treatment. This review describes the selected secondary agricultural products and their utilization for the value-added silica synthesis.