Thiacalix[4]arene-functionalized magnetic xanthan gum (TC4As-XG@Fe3O4) as a hydrogel adsorbent for removal of dye and pesticide from water medium

Abstract

A novel thiacalixarene-functionalized biopolymer nanocomposite hydrogel was designed and prepared as an efficient adsorbent system to elimination of aquatic areas from chlorpyrifos (CPF) and crystal violet (CV). This adsorbent system was conducted by multi-step including; preparation of Fe3O4@XG hydrogel through in-situ magnetization of XG, amine modification of Fe3O4@XG hydrogel by using 3-aminopropyltriethoxysilane (APTES) to get Fe3O4@XG-NH2, the synthesis of TC4As supramolecule, its functionalization with epichlorohydrin (ECH) and eventually covalently attachment of ECH-modified TC4As onto as-prepared Fe3O4@XG-NH2 to obtain the TC4As-XG@Fe3O4 nanocomposite hydrogel. Several characterization techniques including FTIR, XRD, FESEM, VSM, TGA, and BET demonstrated the successful synthesis of TC4As-functionalized XG nanocomposite hydrogel. The result of characterization demonstrated that the TC4As-XG@Fe3O4 adsorbent system showed superparamagnetic property with magnetic saturation (Ms) of 9.10 emu/g and high thermal stability with 73 % char yields. The XRD pattern of TC4As-XG@Fe3O4 nanocomposite showed characteristic peaks of Fe3O4 MNPs and XG, but with enhanced crystallinity in compared to neat XG as result of in-situ magnetization of XG as well as its functionalization with TC4As. The BET surface area of Fe3O4@XG and TC4As-XG@Fe3O4 hydrogels was measured approximately 45.32 and 17.30 m2/g, which was higher than neat XG. Then, the constructed adsorbent system was assessed for removing a CPF as an organophosphorus pesticide and CV as cationic dye from aqueous. The batch adsorption experiments were conducted to optimize the effective adsorption parameter i.e., solution pH, adsorbent dosage, contact time, CPF and CV initial concentration. Furthermore, Freundlich isotherm mode was well-fitted model and by utilizing prepared adsorbent, and the maximum adsorption capacities of CPF and CV (at optimum conditions: 298 K, pH 7.0 and 9.0) were found to be about 769.230 and 833.33 mg/g, respectively. The adsorption kinetic study revealed that experimental data were well-fitted by the pseudo-second-order model. Based on proposed mechanism, the CPF and CV were adsorbed onto hydrogel nanocomposite mainly through π–π interactions, electrostatic interaction and hydrogen bonding. The regeneration experiments up to three cycles were best achieved for two studied pollutants.