Cost-effective adsorbents for dye remediation: Recent breakthroughs and future prospects

Water pollution caused by synthetic dyes from textile, pharmaceutical, paper, and tannery industries remains a major environmental challenge due to persistence, toxicity, and complex chemical structures of these compounds. It is estimated that approximately 700,000 tons of dyes are produced annually worldwide, with 10-15% being discharged into aquatic environments as industrial effluents. Unlike previous reviews that mainly emphasize adsorption capacity, this review addresses critical practical gaps by evaluating economic viability, regeneration capability, scalability, and technology readiness of cost-effective adsorbents for dye remediation. Recent advances in low-cost adsorbents, including biochar, industrial by-products, agricultural wastes, activated carbons, and nanomaterials are systematically analyzed regarding synthesis methods, surface modification approaches, and performance under realistic conditions. Comparative assessment reveals that biochar-based adsorbents typically achieve 85–95% dye removal at costs 60–70% lower than commercial activated carbon, while nanomaterial-based systems demonstrate superior removal efficiencies (>98%) but encounter scalability, cost, and recovery challenges. By integrating performance metrics with economic and practical considerations, this review offers guidance for developing sustainable and commercially viable adsorption-based technologies for industrial dye wastewater treatment.