Keggin型磷钨杂多酸功能化离子盐在模拟太阳光辐照下光催化降解DNT废水

Photocatalytic Degradation of DNT Wastewater by Keggin-Type Phosphor-Tungsten Heteropolyacid Functionalized Ionic Salts under Simulated Sunlight

摘要: 通过离子液体与Keggin型磷钨杂多酸(H₃PW₁₂O₄₀)离子交换形成非水溶性有机阳离子盐，实现Keggin型磷钨杂多酸离子的固定化，探究其光催化降解2,4-二硝基甲苯(DNT)废水的性能。以N-甲基咪唑为起始原料，经过二步合成1-甲基-3-乙酸甲酯基咪唑磷钨酸盐(MEImPWO)和1-甲基-3-烯丙基咪唑磷钨酸盐(MAImPWO)，利用红外光谱仪和扫描电镜对其结构和形貌进行表征；考察了不同光照时间、催化剂用量、H₂O₂用量条件下，所合成离子盐在氙灯光源辐照下光催化降解DNT的性能。结果表明：所合成两种离子盐具有Keggin型磷钨杂多酸特征结构和咪唑结构；MEImPWO呈纳米棒状堆积，MAImPWO呈微米片状和纳米类球状颗粒堆积；两种盐都显示出具有在H₂O₂参与下、自然PH值条件下光催化降解DNT的良好性能。所得最佳的光催化条件和结果为：DNT水溶液(100 mg/L) 50 mL，MEImPWO 0.10 g + H₂O₂ 0.48 g/L，光照1 h，DNT降解54%，光照4 h可使DNT完全降解；MAImPWO 0.10 g + H₂O₂ 0.60 g/L，光照1 h，DNT降解62%，光照3 h可使DNT完全降解。两种催化剂在最佳条件下重复使用5次后，其光催化活性基本保持不变。

Abstract: Non-water-soluble organic cationic salt of Keggin-type phosphorus tungsten polyacid was formed through the ion exchange reaction with an ionic liquid to realize the immobilization of Keggin-type phosphorus tungsten polyacid ion, and the photocatalytic performance of the ionic salts as obtained on the degradation of 2,4-dinitro toluene(DNT) wastewater was explored. With N-methylimidazole as the starting material, 1-methyl-3-methyl acetate-imidazole phosphotungstate (MEImPWO) and 1- methyl-3-allyl-imidazole phosphotungstate (MAImPWO) were synthesized through two steps respectively. Their structure and morphology were characterized by infrared spectrometer and SEM; and their performance on the photocatalytic degradation of DNT under xenon lamp light irradiation was investigated under the conditions of different light time, catalyst amount and H₂O₂ amount. The results show that the two synthesized salts have Keggin characteristic structure and imidazole structure; the morphology of MEImPWO is nanorod accumulation, and MAImPWO is micron sheet and nano spherical particles accumulation; both salts show good performance on the photocatalytic degradation of DNT with the participation of H₂O₂ and natural PH. The better photocatalytic conditions and results are: for MEImPWO, with the amount of catalyst 0.10 g, H₂O₂ 0.48 g/L, light irradiation 1 h, the rate of DNT degradation was 54%, and DNT was completely converted within 4 h; for MAImPWO, with the amount of catalyst 0.10 g, hydrogen peroxide 0.60 g/L, there was 62% of total DNT degraded after 1 h light irradiation, and DNT was completely degraded within 3 h. The photocatalytic activity of the catalysts was basically kept unchanged after 5 cycles under the same conditions.