Foam Ceramics Load And Modified TiO₂ Photocatalytic Degradation Of Boscalid In Water

Most pesticides belong to persistent organic pesticides, they are among the most dangerous and highly toxic pollutants that can cause a series of negative effects, especially serious enough to cause death in animals and humans disease, deformed children. In current, the pesticide is developing toward the trend of hydrolysis, photolysis, and oxidation resistance, which brings great challenge to water pollution.Boscalid is a highly efficient, lasting new neonicotinoid broad spectrum nicotinamide fungicides, because of its high activity, work fast, broad spectrum sterilization, it has active characteristics for almost all types of fungal disease, thus it ia used widely; however, its half-life period is about 28 d-200 d, belonging to the persistent organic pesticides, and the researches on this new pesticides has rarely reported at home and abroad.This topic explored the application prospect of nitrating modification application prospect of TiO2 photocatalysis oxidation technology, based on sunlight as the light source to treat pesticide boscalid in water, carrying out the experimental study about the influence factors of the modification of catalysts, catalytic efficiency, loading of catalyst and so on, the results are as follows:1.The research of nitrogen-doped TiO2 by sol-gel.This experiment adopted ceramic foam as a carrier, tetraisopropyltitanate as a titanium precursor, urea as a nitrogen, boscalid as the target degradation. The nitrogen-doped TiO2 was prepared by sol-gel. The effect of calcination temperature, calcination time and the amount of nitrogen-doped on TiO2 was studied systematically. The property of TiO2 was determined by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Ultraviolet visible diffused reflection (UV-vis).The results showed that, the optimal conditions for preparing the TiO2 is calcining temperature 500℃, calcination time 4h, mixed with 20% nitrogen. Comparing the TiO2 prepared under optimum conditions as the catalyst with other preparing condition, photocatalytic degradating boscalid under xenon lamp,2 h achieved its greatest efficiency.2. The research of boscalid degradation by the modified TiO2 in water.Through single factor to explore initial solution pH, amount of catalyst, boscalid initial concentration and aeration conditions on the photocatalytic degradation efficiency of boscalid.The results showed that, with the increase in pH, boscalid degradation efficiency increased; photocatalytic efficiency optimum amount of catalyst was 0.5 g/L; with boscalid initial concentration increased, the degradation efficiency decreased; after air exposured, boscalid degradation efficiency increased; exposuring nitrogen had no effect.3. The research of common anions and cations on the impact of boscalid degradation.The results showed that, boscalid degradation efficiency increased the impact of common anions Cl", NO3-, SO42" on boscalid degradation efficiency was not obvious, while CO32" had inhibition for the degradation of boscalid, and with the CO32- concentration increased, the inhibition larger; the impact of common cations Na+, K+ on boscalid degradation efficiency was not obvious, while Ca2+, Mg2+ had inhibition for the degradation of boscalid, and with the Ca2+, Mg2+ concentration increased, the inhibition larger.4. The research of supported and powdered TiO2, modified nitrogen-doped TiO2 and P25 on the impact of boscalid degradationThe results showed that, after the reaction 180 min, photocatalytic degradation efficiency of boscalid in the order of powdered TiO2> Supported TiO2, doped with nitrogen 20% TiO2> no nitrogen-doped TiO2> P25 TiO2; the efficient of powdered TiO2 was higher than loaded TiO2. However, loaded TiO2 catalysts was easy to separate from water, so they had higher practical value. Meanwhile, after the addition of urea on TiO2, its utilization for visible light was greatly improved.5. The research of Catalyst reusabilityIt was found that when increasing the frequency of use for the same TiO2, the degradation rate of boscalid corresponding gradually reduced, after using five times, the degradation efficiency decreased from 52.35% to 17.98%, indicating that the poor stability of the catalyst, low utilization ratio, it needed further improvement.6. The research of boscalid degradation intermediatesIt was found that the process of photocatalytic degradation of organism bacteria acyl amine accorded with the Langmuir-Hinshelwood (LH) first-order kinetic model, first order reaction kinetics equation was lnC0/Ct=0.0032x+0.1126, half-life period was 216.61 min. Compared its half-life in filed, the photocatalysis had more practical value. By analysising boscalid photocatalytic degradation efficiency and boscalid TOC removal found that before boscalid was completely oxidized and decomposed, it was first convert into some intermediate product, then gradually oxidative decomposition. Analysising boscalid samples in degradation process by mass spectrometry, combining with relevant literature, proposed the degradation pathways of boscalid.The experimental results show that under simulated sunlight, the foam ceramics load and N-modified TiO2 had a ceramic foam load of better degradation effect for boscalid.