Insight of chitosan-based nanocomposite for removal of hexavalent chromium from wastewater- a review

Chromium occurs in a variety of oxidation states, including hexavalent chromium as a natural contamination of high toxic quality and portability. The release of chromium into the aqueous medium through effluents from industries such as tanneries, textiles, mining, painting, printing, photography and medicinal industries. Clean removal of chromium from the industrial wastewater treatment process is a challenge due to improper selection of technologies from economic, technical and environmental aspects. Adsorption is a very promising and efficient technology for the removal of hexavalent chromium from wastewater. Chitosan as the only polycation coming from renewable resources is endowed with intrinsic valuable properties, such as: biocompatibility, biodegradability, low cost, easy availability, and high reactivity due to plenty of the reactive functional groups (-NH2 and-OH). Due to its solubility in a slightly acidic environment, its ability as an adsorbent for wastewater treatment is hindered. The preparation of nanocomposites with organic and inorganic nanomaterials inhibits the solubility of chitosan in the acid media and could be used to remove Cr(VI) with high adsorption efficiency, non-toxicity, biodegradability and availability. This review outlines recent advances in polymer-grafted chitosan, magnetic chitosan, clay-chitosan, and carbon (multiwall carbon nanotube and graphene oxide)-chitosan nanocomposites and their use in removing toxic Cr (VI) from solution and wastewater. Special emphasis was given to their adsorption capacity, kinetics and adsorption isotherm of Cr (VI) removal. By analysing the various process mechanisms and variables, we appear to demonstrate that nanocomposites can overcome chitosan 's limitations as an adsorbent.