A Comprehensive Review of Effective Adsorbents Used for the Removal of Dyes from Wastewater

Aim: The objective of the review paper aims to explore and provide insight into various low-cost adsorbents prepared and used in the removal of hazardous dye pollutants from the contaminated industrial effluents. Background: The major untreated discharge from the textile industries constitutes a wide range of organic contaminants with the enhanced concentration of biological oxygen demand and chemical oxygen demand in the water bodies. Dyes are considered the major water contaminants and this quest the researchers to adopt various technologies to remove the hazardous dye pollutants from the aquatic environment. Dyes are the chemical compounds that tend to adhere themselves to metal or salts by covalent bond formation or complexes by mechanical retention or physical adsorption so as to impart colours to which it is being applied. Objective: The use of numerous treatment methodologies which have been applied to the degradation of dyes. The current study has been focused on the distinct low cost and cost-effective adsorbents used in the removal of various dye pollutants. Moreover, the application of nanoparticles in the removal of the hazardous dye pollutants had received great interest because of its size and high reactive nature. Methods: The treatment technologies used in the removal of dye pollutants from wastewater have been listed as adsorption, coagulation, electrocoagulation, flocculation, membrane filtration, oxidation and biological treatment. Results: The complex structure of the dyes causes a great harmful impact on the aquatic environment. Though numerous treatment technologies have been applied, adsorption has been preferred by various researchers because of its cost-effective nature. Conclusion: The various adsorbents are used in the removal of cationic, anionic and non-ionic dyes. The different types of adsorbent from agricultural waste, activated carbons, nanomaterials and biomaterials have been discussed with the advantages and limitations.