Lignin and Chitosan-Based Materials for Dye and Metal Ion Remediation in Aqueous Systems

In view of dwindling fresh water sources, water pollution due to dyes and toxic metals is cause for concern. The increase in industrial activity around the world results in the emission of dyes and toxic metals into the aquatic environment and exerts pressure on water treatment plants. The removal of these contaminants is problematic because they can be available in very low concentrations, and water treatment plants are not designed to remove them effectively. A number of approaches including coagulation, precipitation, membrane filtration, and activated carbon adsorption, have been used for the remediation of contaminated water, but these methods are generally limited by high cost and poor selectivity. Lignin- and chitosan-based nanocomposites are potentially useful for these applications because they have minimal environmental footprints, are cost effective, and are compatible with a wide range of materials in composites. Laboratory scale experiments carried out to evaluate these materials have shown that the composites of these materials have remarkable dye and heavy metal (HM) removal capacities, thus making the technology accessible and potentially manageable at a large scale. Using Web of Science, Scopus, Sciencedirect, Springer, and Google Scholar, we evaluated literature on (1) the prevalence and environmental and health impact of pollution due to dye- and metal-laden effluents, (2) available remediation technologies, (3) the synthetic pathways for different chitosan-based nanocomposites, and (4) the potential of chitosan-based nanocomposites for dye and HM removal. There has been a gradual increase in the research of the use of lignin/chitosan-based adsorbent, showing the rapid interest and potential in the materials.