Removal of an Azo Textile Dye from Wastewater by Cyclodextrin-Epichlorohydrin Polymers

Abstract

Native cyclodextrins (CDs), α-, β-and γ-CDs, were employed to synthetise three different cyclodextrin-based polymers using epichlorohydrin (EPI) as a cross-linker. These polymers were applied as adsorbent material to remove an azo textile dye, Direct Blue 78 (DB78), from water. The formation of inclusion complexes between the alone CDs and DB78 molecules were first studied in aqueous solutions. Then, adsorption experiments of the dye were performed by means of cyclodextrin/epichlorohydrin (CD/EPI) polymers. The effects of various parameters, such as contact time, adsorbent dosage, initial dye concentration, pH and temperature, were examined to determine the better adsorption conditions. The equilibrium isotherms and the adsorption kinetics were also analysed using opportune mathematic models. The chemical-physical characteristics and the morphology of the adsorbent polymers were, respectively, observed by differential scanning calorimetry and field emission scanning electron microscope. The CD/EPI polymers showed a very good ability in the removal of DB78 from aqueous solution; indeed, the maximum efficiencies in the dye removal were found to be about 99% for β-CD/EPI polymer and about 97% for γ-CD/EPI polymer, at pH 6 and 25°C conditions. It is possible to assume that the good adsorbent aptitude of CD/EPI polymers is due to their double peculiarity to include the dye in the inner cavity of CDs and to adsorb the dye on their porous surfaces by physical interaction.

Factors Affecting Synthetic Dye Adsorption; Desorption Studies: A Review of Results from the Last Five Years (2017–2021)

“…Chemical methods are: catalytic reduction, coagulation/flocculation, electrochemical reduction, photolysis/photochemical reduction, advance oxidation processes, ultraviolet irradiation ozonation, clay minerals and zeolites. Biological methods can be divided to phytoremediation and microbial remediation (bacterial, algae, fungi, mycoremediation, enzyme degradation and phycoremediation) [5,37,96].…”

“…Molecules 2021, 26, x FOR PEER REVIEW 10 of 32 methods can be divided to phytoremediation and microbial remediation (bacterial, algae, fungi, mycoremediation, enzyme degradation and phycoremediation) [5,37,96].…”

Nanomaterials for Potential Detection and Remediation: A Review of Their Analytical and Environmental Applications

“…All native CDs, α, β, and γ-CDs, were used as precursors to synthesize NSs, where epichlorohydrin (EPI) acted as a cross-linker [139]. The three cyclodextrin-based polymers were used as adsorbent materials to remove Direct Blue 78 from wastewater.…”

A Comprehensive Strategy for Stepwise Design of a Lab PROTOTYPE for the Removal of Emerging Contaminants in Water Using Cyclodextrin Polymers as Adsorbent Material

“…This results in both hydrophilic and hydrophobic properties attributed to the presence of glucose units (CDs) and primarily hydroxyl groups and, the methyl groups and ether bonds of the cross-linking agent, as well as CD-glyceryl bonds, respectively. Therefore, they have been widely applied for environmental purposes, in line with the One Health European strategy, particularly in the removal of heavy metals by complexation, electrostatic interactions, ion exchange, or via covalent bonding to external hydroxyl groups that provide an acidic media [ 28 , 29 , 30 ]; and other EPs recurrent in aqueous media such as dyes [ 31 , 32 , 33 ], pesticides [ 34 , 35 , 36 ] and other micropollutants [ 26 , 37 , 38 ]. Despite how successful the adsorption of ECs on CD polymers is, not many pilot-scale demonstrations have been published [ 38 ].…”