光催化和吸收组合工艺净化丙酮气体的研究

Study on the purification of acetone gas by the combined process of photocatalysis and absorption

为了获得"光催化"与"吸收"联合净化VOCs气体的最佳组合工艺,首先以泡沫陶瓷为载体,羧甲基纤维素钠为黏结剂,采用浸渍-黏结法制得TiO2/泡沫陶瓷光催化材料,然后在自制的VOCs气体净化系统中,选择水溶性的丙酮气体为代表性VOCs气体,以水为吸收剂,考察了"光催化"与"吸收"不同组合工艺对丙酮气体的净化性能,并借助GC/MS和LC/MS手段对尾气和吸收液中的产物相进行分析测定。结果表明,纳米TiO2在泡沫陶瓷上的平均负载率为3.5%,且主要集中负载于陶瓷孔隙附近。不同组合工艺对丙酮气体的净化效率由高到低依次为"光催化+吸收""吸收+光催化""吸收""光催化",其中在"光催化+吸收"最佳工艺条件(液气比为5 L/m3、停留时间为6 s、光照强度为60W)下,丙酮气体的最高去除率达93.7%以上。气相和液相产物分析结果表明,丙酮气体经"光催化"处理后会产生O3和CH3COOH中间产物,但CH3COOH的产生量很少,在以"光催化"为末端工序的尾气中难以测出,而在以"吸收"为末端工序的循环吸收液中反而能检出。在此基础上,给出了"光催化+吸收"净化工艺的反应机理方程。研究得出,"光催化+吸收"工艺组合不仅可实现丙酮气体的高效净化,而且可避免"光催化"末端工序带来的O3和CH3COOH二次污染问题。

To obtain the best combination process of"photocatalysis"and "absorption"for purifying VOCs gas,this paper first prepared the TiO2/foam ceramics photocatalysts by a dip-coheringmethod in which the carrier is foam ceramics and the binder is carboxymethyl cellulose. Then,water-soluble acetone was selected as the representative VOCs gases,and water was used as the absorbent in a self-made VOCs gas purification system. The purification properties of acetone gas obtained by different combined processes of "photocatalysis"and "absorption"were investigated. GC/MS and LC/MS were used to analyze and determine the products in the exhaust gas and the absorption solution,respectively. The results show that the average loading rate of nano TiO2 on foam ceramics is 3. 5%,and they are mainly loaded near the pores of ceramics. The sequence of purification efficiency of acetone gas by obtained different combined processes is"photocatalysis + absorption">"absorption + photocatalysis">"absorption">"photocatalysis". Under the best process conditions( the liquid-gas ratio is 5 L/m3,the residence time is 6 s,and the light intensity is 60 W) for "photocatalysis + absorption",the maximum removal rate of acetone gas is more than 93.7%. The analysis results of the products in the exhaust gas and the absorption solution show that the intermediate products of O3 and CH3COOH can be produced when the acetone gas is treated by the "photocatalysis " process. But the little amount of CH3COOH can not be detected in the tail gas of the combined process with the end process of"photocatalysis". On the contrary,it can be detected in the circulating absorption liquid of the combined process with the end process of"absorption". On this basis,the reaction mechanism equations of the"photocatalysis +absorption"purification process are given. It is found that the combined process of "photocatalysis + absorption"can not only achieve efficient purification of acetone gas but also avoid secondary pollution problems from O3 and CH3COOH produced by the end process of"photocatalysis".