Zn2SiO4-ZnO-生物炭复合物的制备及其可见光催化H2O2降解甲硝唑

Preparation and Visible-light Photocatalytic Degradation on Metronidazole of ZnSiOZnO biochar Composites

以松木碱解液代替NaOH溶液作为锌盐沉淀剂,采用水热法制备了Zn2SiO4-ZnO-生物炭三元复合材料(SOB-x-y, x代表松木粉的用量, y代表NaOH浓度),通过不同手段对样品进行表征,研究了光催化H2O2降解甲硝唑的性能。结果表明,制备的催化剂由枣核状硅锌矿型Zn2SiO4介晶、多边形六方晶相ZnO和松木生物炭构成;与纯六方晶相ZnO相比,它具有更大的比表面积与孔容、更小的带隙能和更弱的荧光发射,因而具有更好的光催化活性。Zn2SiO4-ZnO-生物炭对甲硝唑的光催化H2O2降解过程符合准一级动力学方程,其催化活性随NaOH浓度的增大而提高,随松木粉用量的增加先增加后减小,以SOB-3-4的性能最优。SOB-3-4的速率常数(k)和降解率(h)随pH的降低而增大,随H2O2浓度的升高而增大,随催化剂用量的增加先增大后减小;甲硝唑的降解率随其初始浓度的升高逐渐越低。当初始pH为3、催化剂用量为0.4 g/L、H2O2投加浓度为80 mmol/L及甲硝唑初始浓度为300 mg/L时, k为2.68×10–2 min–1,反应3 h后h达到99.70%。本研究结果对处理难降解制药废水提供了重要的实验依据。

Using pine alkali hydrolysate to replace NaOH solution as zinc salt precipitator, the Zn2SiO4-ZnO- biochar(SOB-x-y, x is the dosage of pine powder, while y is the concentration of NaOH) ternary composites were prepared by hydrothermal method. The photocatalysts were characterized by different methods. The degradation of metronidazole over the H2O2 photocatalysis was studied. Results showed that the as-prepared photocatalysts were composed of jujube-type willemite Zn2SiO4 mesocrystals, hexagonal ZnO and pine biochar. Compared with pure hexagonal ZnO, the SOB-x-y photocatalysts has better H2O2 photocatalytic activity due to the higher surface area and pore volume, lower band gap energy, lower PL emission peak intensity. Metronidazole degradation using the H2O2 photocatalysis was well-fitted to a pseudo-first-order kinetic model by SOB-x-y. Its catalytic activity increased with the increase of NaOH concentration, and increased at first and then decreased with the increase of pine flour content. The SOB-3-4 has best photocatalytic acitivity. Meanwhile, rate constant(k) and degradation rate(η) of SOB-3-4 increase with the decrease of pH, increase with the increase of H2O2 concentration, increase firstly and then decrease with the increase of catalyst dosage. Degradation rate of metronidazole gradually decreases with the increase of its initial concentration. Under the optimal condition(pH=3, catalyst dosage of 0.4 g/L, H2O2 dosage of 80 mmol/L, initial metronidazole concentration of 300 mg/L), k value was 2.68×10–2 min–1 and η reached 99.70% after reaction for 3 h. This study provides an important experimental basis for the treatment of pharmaceutical wastewater.