Advances in nanocomposite and nanostructured chitosan membrane adsorbents for environmental remediation: A review

Chitosan (CS), as a biopolymer, presents unparalleled capabilities for chemical and mechanical modifications to create innovative features, functions, and applications, particularly in preparation of the state-of-the-art membrane adsorbents. CS-based membrane adsorbents have emerged as effective and promising engineering tools for the removal of different pollutants such as dyes and heavy metals from aqueous environments. To date, a great deal of research has been oriented to enhance the adsorptive properties, permeability, physicochemical stability, and sustainability of CS-based membranes by using different types of nanoparticles (NPs). Moreover, NPs can be utilized to tailor the structure and functionality of the nanostructured and nanofibrous CS-based membranes. The current review is focused on the application of different types of NPs, including four main classes of metal-based, carbonic (carbon-based), non-carbon mineral, and MOFs in CS-based membrane adsorbents, applied for liquid phase separations. Literature survey disclosed that researchers have shown an increased interest in non-carbon mineral NPs, while MOFs have emerged as a promising modifier in recent applications. Preparation techniques together with the effects of the NPs inclusion on the chemistry, morphology, adsorption kinetics, and removal capacity of CS-based membranes have also been reviewed and discussed. This review can be a guideline for the researchers to select suitable NP modifiers as well as preparation methods for synthesizing nanocomposite CS membrane adsorbents for various applications. Also, possible interactions of different NPs with the polymeric background have been spotlighted. Thus, this work can help better understanding of the adsorption mechanisms proposed by the CS-based membranes modified with NPs.