Decolorisation of aqueous dye solutions by low‐cost adsorbents: a review

Effluent generated by the textile industry can be highly coloured. Before the waste is disposed into receiving waters, colour removal is an important consideration. Because of their complex molecular structures, dyes present in the textile wastewater are not removed easily by conventional wastewater treatment processes. They are fairly stable to light, as well as heat, and resist biodegradation, thus posing a challenge to conventional physico‐chemical and biological treatment methods. Although adsorption technology using activated carbon has been considered to be an effective and proven technology, it has its limitations as it is expensive and necessitates regeneration. As cost is an important consideration in most developing countries, efforts have been made to explore the possibility of using various low‐cost alternatives that are biodegradable, abundant, readily available, and are derived from waste materials. This article is a compilation of the investigations carried out by numerous researchers (from 2002 onwards) on the effective use of different kinds of low‐cost adsorbents for the removal of specific dyes from textile wastewater.