Chen C C, Lu C S, Chung Y C, Jan J L
Department of General Education, National Taichung Nursing College, Taichung 403, Taiwan.
J Hazard Mater. 2007 Mar 22;141(3):520-8. doi: 10.1016/j.jhazmat.2006.07.011. Epub 2006 Jul 14.
The photodegradation of malachite green (MG), a cationic triphenylmethane dye, is examined both under different pH values and amounts of TiO(2). After 15W UV-365nm irradiation for 4h, ca. 99.9% of MG was degraded with addition of 0.5gL(-1) TiO(2) to solutions containing 50mgL(-1) of the MG dye. The HPLC-PDA-ESI-MS technique was used to obtain a better understanding on the mechanistic details of this TiO(2)-assisted photodegradation of the MG dye with UV irradiation. Five intermediates of the process were separated, identified, and characterized for the first time. The results indicated that the N-de-methylation degradation of MG dye took place in a stepwise manner to yield mono-, di-, tri-, and tetra-N-de-methylated MG species generated during the processes. Under acidic conditions, the results indicated that the photodegradation mechanism is favorable to cleavage of the whole conjugated chromophore structure of the MG dye. Under basic conditions, the results showed that the photodegradation mechanism is favorable to a formation of a series of N-de-methylated intermediates of the MG dye.
研究了阳离子三苯甲烷染料孔雀石绿（MG）在不同pH值和二氧化钛用量下的光降解情况。在15W紫外365nm光照4小时后，向含有50mgL(-1) MG染料的溶液中添加0.5gL(-1)二氧化钛，约99.9%的MG被降解。采用高效液相色谱 - 光电二极管阵列 - 电喷雾质谱联用技术（HPLC - PDA - ESI - MS），以便更好地了解在紫外光照射下二氧化钛辅助MG染料光降解的机理细节。首次分离、鉴定并表征了该过程的五种中间体。结果表明，MG染料的N - 去甲基化降解以逐步方式进行，在此过程中产生单、二、三、四N - 去甲基化的MG物种。在酸性条件下，结果表明光降解机理有利于MG染料整个共轭发色团结构的裂解。在碱性条件下，结果表明光降解机理有利于形成一系列MG染料的N - 去甲基化中间体。
