Crosslinked cyclodextrin as potent composite for removal of wastewater pollutants

Abstract

Purpose of Review: Pollution from wastewater is a perpetual environmental issue worldwide that negatively impacts the ecosystem and human beings. The use of natural-based compounds such as cyclodextrin (CD) to remove pollutants from water and wastewater systems has been reported by various researchers. Nevertheless, its direct use in wastewater treatment is hampered by its water-soluble properties. Beta-cyclodextrin (ß-CD) is a cyclic oligosaccharide compound that can effectively trap pollutants from wastewater by the formation of truncated inclusion complex with various molecules. Hence, it is the motivation of this article to review the effectiveness and the recent strategies of crosslinked-ß-CD toward remediation of various pollutants from wastewater. Recent Findings: The crosslinked-ß-CD was found as an improvement for native ß-CD in the purpose of wastewater pollutant remediation. Strategies in chemical crosslinking include the choice of suitable crosslinkers, the type of support materials, and surface modifications. It was observed that different strategies resulted in various degrees of performance of the composite ß-CD adsorbents. The efficiency of adsorption process was influenced by the operational parameters such as pH, contact time, and initial pollutant concentration, whereby it was characterized by the recyclability, adsorption capacity, and mechanical strength. The emergence of nanotechnology has led to a great improvement to the existing composite-ß-CD adsorbent by providing a large surface area, where it can be easily functionalized and modified toward the targeted molecules. Summary: Crosslinking is a versatile method for developing a composite-ß-CD adsorbent for pollutant uptake as it employs a simple technique and performs a simple separation process with moderate operational conditions. Graphical Abstract: The 3D structure of ß-cyclodextrin resembles a truncated cone, having characteristics of hydrophilic surface and hydrophobic cavity and capable to trap molecules inside its cavity. The graphical abstract shows the flows of this review paper. The crosslinking strategies, the operational parameters, and the adsorption performance of the composite CD-adsorbents were reviewed and discussed.