Adsorptive approaches for silicon recovery from industrial wastewater: materials, mechanisms, and recent advances

Different silicon-containing substances present in wastewater streams used in various industrial applications are reported to be responsible for membrane fouling, scaling, and operational difficulties, thus requiring appropriate removal processes. From different techniques, adsorption has proved to be an interesting method for this purpose, characterized by effectiveness, simplicity, and low-cost operation. This paper presents a critical review of recent developments in the field of adsorptive treatment of aqueous systems for their silicon removal. Different types of adsorbents such as activated carbons, metal oxides, clay minerals, zeolites, waste by-products, and nanomaterials are discussed from the point of view of their adsorptive performance and underlying adsorption mechanisms. Factors affecting silicon removal such as pH, temperature, contact time, adsorbent dose, and presence of competitive species are considered. In addition, several issues to be addressed in future studies such as investigation of practical wastewater, regeneration evaluation, and piloting trials are discussed.