Progress in lignin hydrogels and nanocomposites for water purification: Future perspectives

Lignin is one of the most abundant natural polymers after cellulose and has attracted great attention in academia as well as in industry for miscellaneous applications. Lignin also exhibits very high potential as a renewable sustainable resource for a galaxy of high value biochemicals. Due to the typical structure of lignin, it can be converted into different types of useful products. From a ligno-cellulose bio-refinery prospective point of view, it can be regarded as an economic bio product and can also be used as filler in several polymers to form blends or composites. Recently lignin-based hydrogels have shown excellent performance for removal of various pollutants from water. The adsorption properties of lignin based hydrogels can further be improved by using a combination of nanomaterials and lignin that results in promising hydrogel nanocomposites. In nature, the most abundant structures are formed by the combination of lignin, cellulose and hemicelluloses. In this article, we have attempted to comprehensively review the research work carried out in the direction of usage of lignin-based hydrogel for removal of toxic pollutants including metal ions and dyes.