Cyclodextrin-Based Nanosponges as an Environmentally Sustainable Solution for Water Treatment: A Review

Abstract

Over the past few decades, the disposal of various industrial pollutants such as organic dyes, heavy metal ions, pesticides, and phenolic compounds has led to the deterioration of the quality of freshwater; even with the 70% water coverage over the earth, there is meager access to freshwater sources. Against the drawbacks of conventional water purification methods such as sludge production and generation of toxic byproducts, the adsorption process is regarded as an efficient and economical strategy for the treatment of wastewater. Among various available adsorbents, cyclodextrin-based nanosponges have evolved as prominent adsorbents for treating wastewater and are considered a cost-effective option with minimal energy and time requirements. Owing to their porous nature, cone-like structure, cross-linked three-dimensional network, and special architecture of the hydrophilic and hydrophobic moieties wherein the hydrophobic core can form inclusion complexes with pollutants via host−guest interactions while hydrophilic edges interact with pollutants through hydrogen-bonding and electrostatic interactions, they are effective adsorbents for the removal of a variety of pollutants such as heavy metals, organic dyes, phenols, and pesticides. Additionally, the number of active sites in these nanosponges could be enhanced by hybridizing with other adsorbents or by functionalization with magnetic nanoparticles. This review deliberates various water purification methods and underlines the limitations of using other conventional methods over adsorption. The strategies to synthesize β-cyclodextrin-based nanosponges deploying various cross-linkers and their further modifications have been discussed in detail. Finally, the application of these nanosponges for the effective removal of assorted pollutants from wastewater highlighting the adsorption mechanism in certain cases is cogitated.

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“…Extraction of nanometallic pollutants can also be accomplished through strong host–guest interactions. Macrocyclic compounds like CD are strong complexing hosts for hydrophobic guest species . The hydrocarbon chain of the surfactant is an ideal hydrophobic guest for the CD cavity, and the strength of host–guest interactions depends on the best fit model.…”

Enhanced photocatalytic performance of a rGO-Ca2Fe2O5 nanocomposite for photodegradation of emergent pollutants

“…), pesticides, phenols, pharmaceuticals, and antibiotics and their metabolites have been shown to be exceedingly harmful. Due to challenges like low biodegradability, and a protracted lifespan of deterioration in the ecosystem, the resulting contaminants after the treatment are also considered hazardous [8][9][10][11] .Traditional wastewater treatment techniques, including filtration, adsorption, chemical coagulation, biological treatment, flocculation, etc., are typically ineffective at degrading aromatic and heterocyclic groups in their molecular structure. For instance, filtration (such as membrane and depth filtration) suffers from being clogged easily by foreign particles in the wastewater, and regular membrane replacement and filtration processes are often expensive.…”

“…), pesticides, phenols, pharmaceuticals, and antibiotics and their metabolites have been shown to be exceedingly harmful. Due to challenges like low biodegradability, and a protracted lifespan of deterioration in the ecosystem, the resulting contaminants after the treatment are also considered hazardous [8][9][10][11] .…”