Review of Harmful Effects of Colloidal Silica after End Use Application in Environment

Abstract

Colloidal silica is a technologically important inorganic nanomaterial extensively used in coatings, catalysts, polishing agents, paper processing, construction materials, biomedical systems, and numerous advanced industrial formulations owing to its high surface area, chemical stability, tunable particle size, and versatile surface chemistry. Although generally regarded as a lowtoxicity and environmentally acceptable material, its increasing production and widespread discharge have prompted growing interest in its environmental fate and long-term impacts. Unlike bulk silica, colloidal silica remains highly dispersed in aqueous systems due to its small particle size and electrostatic stability, enabling prolonged transport and interaction with natural matrices. This review examines the behavior of colloidal silica in water, soil, sediment, and wastewater environments, highlighting how its physicochemical properties influence turbidity, light penetration, nutrient mobility, soil pore blockage, sediment modification, sludge generation, and treatment inefficiencies. Particular attention is given to indirect ecological effects on aquatic productivity, benthic habitats, microbial processes, and soil functionality, as well as occupational concerns associated with airborne dried residues and concentrated suspensions. Current mitigation strategies including coagulation–flocculation, membrane separation, process optimization, recovery and reuse, controlled discharge, and safe handling practices are also critically discussed. Overall, the environmental risks associated with colloidal silica arise less from acute toxicity and more from persistence, accumulation, and system-level physical interactions. A balanced understanding of these mechanisms is essential for developing sustainable management approaches that preserve the industrial advantages of colloidal silica while minimizing ecological and human health concerns.