Biopolymer-Clay Hybrid Hydrogels in Pharmaceutical Wastewater Treatment: A Critical Review of Modification, Mechanisms and Economic Viability

Abstract

The growing presence of pharmaceutical residues in aquatic ecosystems presents a pressing challenge for environmental and public health, underscoring the need for remediation technologies that are not only effective but also sustainable and economically feasible. Clay-based bio-hydrogels have recently emerged as promising candidates, owing to their adaptable physicochemical properties, natural biocompatibility, and low production costs. This review critically examines recent developments in the design and application of clay-based bio-hydrogel composites, synthesized through the integration of natural clays, their derivatives, and biopolymers such as chitosan, alginate, and lignin, for the adsorption of pharmaceutical contaminants from water. Particular attention is given to clay modification strategies that improve adsorption performance and selectivity, as well as the underlying mechanisms including ion exchange, hydrogen bonding, and π–π interactions that govern pollutant uptake. The review also considers the economic viability of these materials and highlights key research gaps, notably the need for testing under real wastewater conditions and the development of scalable regeneration techniques. By advancing the understanding and application of clay-based bio-hydrogels, this work supports the broader goal of developing green technologies that align with circular economy principles and contribute meaningfully to environmental remediation efforts.