BiVO 4 photocatalysts with distinct morphology were solvothermally prepared by regulating the pH of precursor solution. The physicochemical properties of BiVO 4 catalysts were characterized using XRD, SEM, EDS, FT-IR and UV-Vis DRS. With the assistance of peroxydisulfate (PDS), as-obtained BiVO 4 could effectively degrade the cationic dye rhodamine B (RhB) and the anionic dye methyl orange (MO) under visible-LED-light illumination. RhB degradation obeys the first-order kinetic, while MO degradation complies with the second-order kinetic. Short stick-like BiVO 4 (named as BiVO 4 -1) showed the best RhB degradation efficiency, and sheet-like BiVO 4 (named as BiVO 4 -9) had the highest MO degradation rate. The influence of some important operating factors (PDS dose, BiVO 4 dosage, temperature, inorganic anions and humic acid) on the degradation of RhB and MO were discussed. In the BiVO 4 -1/PDS/Vis system, the free radical pathway (O 2 •‒ , SO 4 •‒ , •OH) and the non-radical pathway ( 1 O 2 and h + ) acted together to realize the degradation of RhB; however, in the BiVO 4 -9/PDS/Vis system, MO degradation was mainly dominated by the non-radical oxidation pathway ( 1 O 2 and h + ).
With increasing concerns on the environment and human health, the degradation of glyphosate through the formation of less toxic intermediates is of great importance. Among the developed methods for the degradation of glyphosate, photodegradation is a clean and efficient strategy. In this work, we report a new photocatalyst by doping F ion on BiVO 4 that can efficiently degrade glyphosate and reduce the toxic emissions of aminomethylphosphonic acid (AMPA) through the selective (P)−C−N cleavage in comparison of BiVO 4 catalyst. The results demonstrate that the best suppression of AMPA formation was achieved by the catalyst of 0.3F@BiVO 4 at pH = 9 (AMPA formation below 10%). In situ attenuated total reflectance Fourier transforms infrared (ATR-FTIR) spectroscopy indicates that the adsorption sites of glyphosate on BiVO 4 and 0.3F@BiVO 4 are altered due to the difference in electrostatic interactions. Such an absorption alteration leads to the preferential cleavage of the C−N bond on the N−C−P skeleton, thereby inhibiting the formation of toxic AMPA. These results improve our understanding of the photodegradation process of glyphosate catalyzed by BiVO 4 -based catalysts and pave a safe way for abiotic degradation of glyphosate.
A novel and short-term preparation method was conducted to fabricate pristine BiVO 4, and Gadolinium (Gd) doped BiVO 4 photocatalysts at sub-100 °C. The optical, structural, morphology, microstructure, and compositional characteristics of the fabricated photocatalysts were examined, which illustrated that the doping of Gd stabilized the existence of the tetragonal phase structure and enlarged the specific surface area of the pristine BiVO 4 . The comparison of the photocatalytic performance, preparation power consumption , and preparation cost showed the superiority of Gd doped BiVO 4 photocatalyst fabricated by the Short-Term Synthesis Method at sub-100 °C. The ofloxacin (OFL) removal rate with 5%, 7%, and 10% Gd-BiVO 4 photocatalysts was 1.53, 1.61, and 1.83 times that with pristine BiVO 4 under sunlight, respectively. The degradation performance of target contaminants, including diclofenac, tetracycline HCl , ofloxacin, rhodamine B, and sulfadiazine, was demonstrated after one hour of sunlight irradiation with 5% Gd-BiVO 4 , achieving the removal efficiencies of 98.63%, 98.07%, 97.98%, 92.09%, and 78.56%, respectively. The effect of various factors on the removal performance was revealed, indicating that SO 4 2− and H 2 PO 4 − had a remarkable inhibitory effect on the degradation. The 5% Gd-BiVO 4 also showed excellent reusability and stability after five-cycle runs. The photogenerated holes (h + ) and the superoxide radicals ( • O 2 − ) were the predominant generated active species , and the possible photocatalytic mechanism for the degradation of organic contaminants was proposed. Simple prepared Gd-BiVO 4 photocatalysts were revealed to be a practical and potential choice for efficiently degrading contaminants with sunlight as green energy.
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