Development of poly(vinyl alcohol) / chitosan / aloe vera gel electrospun composite nanofibers as a novel sorbent for thin-film micro-extraction of pesticides in water and food samples followed by HPLC-UV analysis

Herein, a novel composite of poly(vinyl alcohol) (PVA)/citric acid (CA)/ chitosan (CS)/ aloe vera gel (AV) was fabricated via the electrospinning technique followed by a thermal treatment. The resultant composite...

Colorimetric Detection of Acidic Pesticides in Water

A water-stable, porphyrin-based metal-organic framework (MOF) produces a distinct colour change in response to acids’ pKa and concentrations. This colour change is associated with the protonation of the N-atoms within...

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 β-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 β-CD content, 96.4% swelling, 94.5% paraquat removal, 0.1766 m2 g−1 specific surface area, and 5.2 × 10−4 cm3 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 R2 = 0.9998) and Langmuir isotherm (with R2 = 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.

Removal of selected pesticides from water using granular activated carbon

Pesticides are intensively used for the protection of field crops, orchards and vineyards, but they are also used in the removal of undesirable stands on non-agricultural land (railway embankments, playgrounds, handling areas, etc.), in water management (in coastal management, destruction of growths in irrigation canals), in forestry, etc. Regular application of pesticides increases their content in the aquatic environment and agricultural products. Their occurrence in water is relatively common and it follows that these substances are used in large quantities. Residues of these substances can persist in soils for 2 to 12 weeks. Due to their good solubility in water, they are easily transported from the soil to aquifers. Several methods can be used to remove pesticides from water, e.g., coagulation, filtration, precipitation, ozonation, adsorption, ion exchange, nanofiltration, reverse osmosis and advanced oxidation processes. Their effectiveness varies considerably and depends mainly on the chemical nature of the pesticide being removed. This article studies adsorption on two granular activated carbons Filtrasorb 400 and Norit 1240. Mixture of the pesticide standards (acetochlor, alachlor, dimethachlor, propachlor, metazachlor and metolachlor) was added to drinking water with concentration of approximately 1 µg/L. The experiments were performed in the glass bottles with the volume of 200 mL of water. The granular activated carbons (200 mg) were added to the bottles. Subsequently these bottles were regularly stirred, and the samples were taken out at times 0, 30, 60, 90, 120, 180, 240 and 360 minutes. Samples were taken by pipette into the 40 ml glass vials with added thiosulphate for preservation. Analyses of target pesticides were performed in laboratories of ALS Czech Republic in Prague. LC-MS using the internal standard method was used to determine chlorinated pesticides in water samples. The adsorption efficiency of pesticides removal and the adsorption capacity of granular activated carbon depends on the time of contact of water with the material. The results showed that the efficiency of selected pesticides removal and adsorption capacity for two granular activated carbons used varied. Filtrasorb F400 proved to be a better sorption material than Norit 1240. The efficiency of this material ranged from 18 to 60%, while the efficiency of Norit 1240 was significantly lower. Adsorption capacity of activated carbons for selected pesticides and reaction kinetics of 0th, 1st, 2nd and 3rd order was also studied.