Dye Removal from Aqueous Solution using Low Cost Bioadsorbents Derived from Agricultural Waste: A Review

Abstract

Dyes are the chemical substances which impart color upon the application to the substrate by mechanical retention, physical adsorption, covalent bond formation and complexation with salts. Different approaches for dye removal include chemical approach (electrochemical destruction, ozonation, and Fenton-like oxidation), physical approach (filtration, coagulation, adsorption and ion-exchange) and biological approach (aerobic and anaerobic oxidation, microbial cultures). However, adsorption onto low cost bioadsorbents derived from agricultural wastes in beneficial over other techniques due to sludge free procedure, recovery of adsorbent, more efficient, technically easy and non-polluting characteristics. Agricultural wastes are chemically modified using alkali, acids, oxidizing agents, surfactants; and are modified by physical activation and biological treatments to alter its pore size, physic-chemical properties, chemical composition and surface area to enhance its adsorption potential. This review focuses on various adsorbents derived from agricultural wastes as such and in its chemically modified form for the uptake of dyes from aqueous solution, different factors affecting the uptake of dyes from aqueous solution and thermodynamic parameters for the adsorption process. Mechanism for the dye removal and different adsorption isotherms applicable to its are also presented.