Adsorption of dyes and heavy metal ions by chitosan composites: A review

Various adsorbents have been used to remove different types of dyes and heavy metal ions from wastewater especially those that are harmful to mankind. Activated carbons, plant or lignocellulosic wastes, clays and biopolymers are among the common adsorbents used. Chitosan, a type of biopolymer, is a good adsorbent to remove various kinds of anionic and cationic dyes as well as heavy metal ions. Chemical modifications that lead to the formation of chitosan derivatives, grafting chitosan and chitosan composites have gained much attention, extensively studied and widely reported in the literatures. This review provides relevant literature of the past ten years on the application of chitosan composites for removing dyes and heavy metal ions. A list of chitosan composites with their adsorption capacity and the experimental conditions has been compiled. This review also includes the mechanisms that might be involved during adsorption process.