Adsorption of Paraquat by Poly(Vinyl Alcohol)-Cyclodextrin Nanosponges

The contamination of hydrosoluble pesticides in water could generate a serious problem for biotic and abiotic components. The removal of a hazardous agrochemical (paraquat) from water was achieved by adsorption processes using poly(vinyl alcohol)-cyclodextrin nanosponges, which were prepared with various formulations via the crosslinking between citric acid and beta-cyclodextrin in the presence of poly(vinyl alcohol). The physicochemical properties of nanosponges were also characterized by different techniques, such as gravimetry, thermogravimetry, microscopy (SEM and Stereo), spectroscopy (UV-visible, NMR, ATR-FTIR, and Raman), acid-base titration, BET surface area analysis, X-ray diffraction, and ion exchange capacity. The C10D-P2 nanosponges displayed 60.2% yield, 3.14 mmol/g COOH groups, 0.335 mmol/g beta-CD content, 96.4% swelling, 94.5% paraquat removal, 0.1766 m(2) g(-1) specific surface area, and 5.2 x 10(-)(4) cm(3) g(-)(1) pore volume. The presence of particular peaks referring to specific functional groups on spectroscopic spectra confirmed the successful polycondensation on the reticulated nanosponges. The pseudo second-order model (with R-2 = 0.9998) and Langmuir isotherm (with R-2 = 0.9979) was suitable for kinetics and isotherm using 180 min of contact time and a pH of 6.5. The maximum adsorption capacity was calculated at 112.2 mg/g. Finally, the recyclability of these nanosponges was 90.3% of paraquat removal after five regeneration times.

Automated summary

The study successfully removed a hazardous agrochemical from water using poly(vinyl alcohol)-cyclodextrin nanosponges, displaying good physicochemical properties and high recyclability after multiple regenerations. The adsorption process followed the pseudo second-order kinetics and Langmuir isotherm, with a maximum adsorption capacity of 112.2 mg/g.