Removal of paraquat herbicide from water by textile coated with anionic cyclodextrin polymer

The coating of anionic cyclodextrin polymer on polyethylene terephthalate (PET) textile was achieved by crosslinking between β-cyclodextrin (β-CD) and citric acid (CTR) to adsorb paraquat herbicide from aqueous solution. This coating performance (30 min, 170 °C) was 22.18% of weight gain which was corresponded to 0.51 mmol/g of ion exchange capacity (IEC). Then, the samples were characterized by scanning electron microscopy (SEM), attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) and thermogravimetric analysis (TGA). The appropriated pH was 6.5 and the equilibrium time was 420 min. At 30 °C, the adsorption capacity towards paraquat (PQ) was enhanced (4.5, 18.9 and 23.7 mg/g) when the initial concentration of paraquat was increased (10, 50 and 250 mg/L). The adsorption kinetics was fitted to the pseudo-second-order model and the adsorption isotherm was suitable to Langmuir model. For the thermodynamic studies, the negative ∆G° revealed a spontaneous process, the negative ∆H° showed an exothermic process and the positive ∆S° displayed an enhanced disorder. Finally, the reusability of functionalized textile in methanol was reached 78.6% after six regeneration cycles and the stability of sample in various solvents was also studied. Anionic cyclodextrin polymer coated on PET textile issued from the crosslinking between β-cyclodextrin and citric acid was used as an efficient adsorbent for paraquat removal from aqueous solution.