Degradation of boscalid, pyraclostrobin, fenbuconazole, and glyphosate residues by an advanced oxidative process utilizing ultraviolet light and hydrogen peroxide

Effect of tannic acid binding on the thermal degradation behavior and product toxicity of boscalid

The effect of tannic acid (TA) binding on the thermal degradation of boscalid was studied in this work. The results revealed that TA binding has a significant impact on boscalid degradation. The degradation rate constant of bound boscalid was reduced, and its corresponding half-life was significantly prolonged compared to the free state. Four identical degradation products were detected in both states through UHPLC-Q-TOF-MS, indicating that degradation products were not affected by TA binding. Based on DFT and MS analysis, the degradation pathways of boscalid included hydroxyl substitution of chlorine atoms and cleavage of CN and CC bonds. The toxicity of B2 and B3 exceeded that of boscalid. In summary, the binding of TA and boscalid significantly affected the thermal degradation rate of boscalid while preserving the types of degradation products. This study contributed to a fundamental understanding of the degradation process of bound pesticide residues in complex food matrices.

Ferrihydrite-loaded water hyacinth-derived biochar for efficient removal of glyphosate from aqueous solution

Ferrihydrite-loaded water hyacinth-derived biochar (FH/WHBC) was prepared by in-situ precipitation method to treat glyphosate-containing wastewater. The adsorption properties and mechanism, and actual application potential were deeply studied. Results showed that the adsorption performance of FH/WHBC was closely related with the precipitation pH condition, and the adsorbent prepared at pH 5.0 possessed the highest adsorption capacity of 116.8 mg/g for glyphosate. The isothermal and kinetic experiments showed that the adsorption of glyphosate was consistent with Langmuir model, and the adsorption process was rapid and could be achieved within 30 min. The prepared FH/WHBC was more suitable for application under high acidity environment, and could maintain the great adsorption performances in the presence of most co-existing ions. Besides, it also possessed a good regenerability. Under dynamic condition, the adsorption performance of FH/WHBC was not affected even at high flow rate and high glyphosate concentration. Furthermore, the FH/WHBC can keep excellent removal efficiency for glyphosate in wastewater treatment, and the concentration of glyphosate can be reduced to 0.06 mg·L^-1, which was lower than the groundwater quality of class II mandated in China. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) characterization indicated that the adsorption of glyphosate on FH/WHBC was mainly accomplished through electrostatic adsorption and the formation of inner-sphere complexes. In brief, the prepared sorbent FH/WHBC was expected to be used in the treatment of industrial glyphosate wastewater.

Feasibility of a Heterogeneous Nanoscale Zero-Valent Iron Fenton-like Process for the Removal of Glyphosate from Water

Glyphosate is a widely used herbicide, and it is an important environmental pollutant that can have adverse effects on human health. Therefore, remediation and reclamation of contaminated streams and aqueous environments polluted by glyphosate is currently a worldwide priority. Here, we show that the heterogeneous nZVI-Fenton process (nZVI + H₂O₂; nZVI: nanoscale zero-valent iron) can achieve the effective removal of glyphosate under different operational conditions. Removal of glyphosate can also take place in the presence of excess nZVI, without H₂O₂, but the high amount of nZVI needed to remove glyphosate from water matrices on its own would make the process very costly. Glyphosate removal via nZVI--Fenton was investigated in the pH range of 3-6, with different H₂O₂ concentrations and nZVI loadings. We observed significant removal of glyphosate at pH values of 3 and 4; however, due to a loss in efficiency of Fenton systems with increasing pH values, glyphosate removal was no longer effective at pH values of 5 or 6. Glyphosate removal also occurred at pH values of 3 and 4 in tap water, despite the occurrence of several potentially interfering inorganic ions. Relatively low reagent costs, a limited increase in water conductivity (mostly due to pH adjustments before and after treatment), and low iron leaching make nZVI-Fenton treatment at pH 4 a promising technique for eliminating glyphosate from environmental aqueous matrices.