Advancement of hybrid coagulants for sustainable industrial effluents treatment: Insights and future directions

The growing complexity of industrial effluents necessitates advanced treatment technologies that are efficient, sustainable, and scalable. Among physicochemical methods, solid-liquid separation via coagulation-flocculation remains essential; however, conventional single-component coagulants face challenges such as pH sensitivity, excessive sludge generation, and limited sustainability. Hybrid coagulants, engineered by integrating inorganic salts with synthetic or natural polymers, provide synergistic charge neutralization, adsorption, and bridging functionalities, enhancing pollutant removal and operational performance. This review critically evaluates the evolution of hybrid coagulant design, emphasizing the relationships between synthesis strategies, underlying mechanisms, and treatment performance. The study was conducted through a comprehensive literature survey using multiple scientific databases and search engines, including Scopus, Web of Science, and Google Scholar. Relevant studies were identified using targeted keywords, and quantitative data were extracted and synthesized to assess coagulant and flocculant performance across diverse industrial effluents. Reported hybrid formulations typically achieve 80–100 % removal of turbidity and key contaminants in textile, tannery, petrochemical, pharmaceutical, and agro-industrial wastewaters. Despite these advances, challenges remain in process optimization, scalability, sludge minimization, and environmental impact management. Key considerations, such as life cycle assessment and sludge valorisation, are discussed to support industrial application. Emerging strategies that combine materials innovation with digital optimization provide a roadmap for the development of next-generation hybrid coagulants in sustainable industrial wastewater management.