Dye sequestration from aqueous phase using natural and synthetic adsorbents in batch mode: present status and future perspectives

The progressive use of dyes in various industrial sectors, such as textiles, paints, paper, and personal care products, has posed a severe threat to humankind. Different research groups in the last couple of decades have contributed significantly to providing some solution to such dye contamination. Such reports exhibit varying degrees of removal depending upon experimental constraints. This review article summarizes the dye removal efficiency offered by natural and synthetic adsorbents with a comparative discussion. Natural adsorbents, including plant-based materials, are known for their easy availability, cost-effectiveness, non-toxicity, sustainability, biodegradability, and eco-friendliness. On the other hand, synthetic adsorbents enjoy an edge over natural ones with high surface area, up-scale production, high efficiency, water stability, and specificity. This review comprehensively summarizes the effects of various physicochemical factors, kinetics, and isotherms on adsorption, along with related thermodynamic interpretations. Mechanistic forces that are responsible for adsorbate–adsorbent binding have been interpreted. A comparative study of natural and synthetic adsorbents adds flavor to the entire article. The scope of future work has been suggested with possible solutions. Graphical abstract