Textile dyes removal from wastewater using recent promising composites: A review

Abstract

Dyes are widely used in many fields such as textiles, leather, paper, and plastics. The industries which used dyes consume a large amount of water, and in some textile dyeing operations, as much as 15-20% of dyes used do not attach to the fibers, so they are lost to wastewater, and the resulting colored effluents can represent a serious water pollution problem due to their color content and toxic components which, over time, are directly involved in the degradation of our ecosystem. The usual effluent treatment involves biological systems like activated sludge; however, conventional treatment has not efficiently removed the effluent dye due to the recalcitrant nature of the dyes and the diverse composition of the effluent. Some conventional methods which have been largely used to eliminate dyes ions from various industrial effluents are often costly, especially in removing dye ions from dilute solutions. Adsorption is considered quite attractive in terms of its efficiency of removal from dilute solutions. Recently, various composites have received wide attention due to their outstanding properties in wastewater treatment. However, non-biodegradable synthetic polymers are largely applied as the organic components of these composites, leading to negative environmental impacts. In this paper, after a brief description of textile dyes, their toxicity and the conventional physic-chemical processes used in the degradation of dyes, we have focused on some of the work published over the past 5 years using the most promising composites for environmental purposes. Overall, the biopolymers and magnetic-based composites have demonstrated outstanding removal capabilities for a large range of dyes.