Sustainable Technologies for the Sequestration of Aqueous and Gaseous Pollutants: Role of Chitosan Based Biomaterials

The increasing pollution in aquatic systems with harmful substances and the persistent build up of greenhouse gases in the atmosphere have emerged as major environmental concerns, necessitating sustainable and efficient remediation strategies. The aquatic pollutants in question are highly toxic, persistent, and not easily removed by conventional treatment methods and are therefore a serious threat to aquatic ecosystems and human health. At the same time, carbon dioxide (CO2) levels in the atmosphere have risen, which have led to a strengthening of global warming and climate change. A number of physical, chemical and biological technologies have been developed to remove the aqueous pollutants and to capture CO2, but because of high operating costs, energy consumption, generation of secondary waste, fouling of membranes, and poor regeneration, they are not widely used. Of all the available methods, adsorption is proven to be a simple and efficient method, as it is easily applicable to a wide range of contaminants, is energy efficient, and has a high removal efficiency. This review gives a brief overview of the major pollutants in the aqueous and gas phase, focusing on CO2, their sources, environmental implications, and remediation technologies. The different classes of adsorbent material are discussed with respect to their use in the environment. A particular attention is given to chitosan, which is a renewable, biodegradable biopolymer extracted from abundant biomass containing chitin in nature. Different types of modification methods are discussed in the context of enhancing the adsorption capacity, stability, selectivity and reusability. New composites and hybrid biomaterials for heavy metals, dyes, surfactants, pharmaceuticals and CO2 capture are also discussed. It illustrates the tremendous potential of modified chitosan and other biomaterial based adsorbents as sustainable materials for the removal of pollutants .