• 关键词：TiO₂  茜素黄R  反应机理  PM3算法  紫外-可见光谱  L-H模型

• 基金项目：国家自然科学基金项目(No.20307005,40730949);甘肃省科学技术攻关计划项目(No.2GS057-A52-001-02,0804GKCA029);环境化学与生态毒理学国家重点实验室开放课题(No.KF2008-03)

• 陈强
• 兰州大学大气科学学院, 兰州 730000

• 王芳
• 德州学院化学系, 德州 253023

• 宋俊密
• 兰州大学化学化工学院, 兰州 73000

• 袁九毅
• 兰州大学大气科学学院, 兰州 730000

• 摘要：以纳米TiO₂(P25)粉末作为催化剂光降解茜素黄R.GC-MS和LC-MS检测结果表明,有3种可能的降解途径:①茜素黄R(C₁₃H₈N₃O₅Na)水解生成的C₁₃H₈N₃O₅-(H)与光催化产生的.OH自由基发生取代反应生成C₁₃H₈N₃O₆-(I)和C₁₃H₈N₃O₇-(J),进一步脱羧分别生成C₁₂H₉N₃O₄(L)和C₁₂H₉N₃O₅(M);②H分子发生脱羧反应生成C₁₂H₉N₃O₃(K),进一步反应生成C₁₂H₁₁N₃(C)和C₁₂H₁₂N₂(D);③H分子中氮氮键发生断裂而生成C₆H₆N₂O₂(A)、C₆H₄N₂O₄(B)、C₆H₈N₂(E)、C₆H₆O(F)和C₇H₇NO₃(G).所有生成的中间产物被继续降解,最终矿化为CO₂和H₂O等无机小分子物质.利用MolecularOrbitalPACkage中的PM₃半经验方法对茜素黄R分子构型优化计算,结果表明,茜素黄R的羧基净电荷密度为-0.680,在实验条件下(pH为2.86)羧基易吸附在TiO₂表面,而成为.OH进攻的最有利位置,实验检测到羟基化的产物(J和I).茜素黄R的羧基和苯环相连的C—C键长最长,反应过程中易发生脱羧反应,实验检测到脱羧后的产物(K);—NN—键长较长,易断裂生成芳胺类化合物(A,E,G等).茜素黄R带羧基和羟基的苯环电荷密度为-0.160,带硝基苯环电荷为-0.165,易吸附在催化剂表面而被自由基进攻,生成羟基化产物.计算结果和实验检测结果一致.动力学研究表明,茜素黄R光催化降解的动力学符合Langmuir-Hinshel wood模型计算的结果.

• Abstract：Alizarin yellow Rwas photodegraded over nano-TiO₂ powder as catalyst and the reaction intermediates were analyzed by GC/MSand LC/MS.Based on the results,three potential photocatalytic degradation pathways were identified for Alizarin yellow R.The hydrolyzed product of Alizarin yellow R,C₁₃H₈N₃O₅^-(H) reacted with OHto generate C₁₃H₈N₃O₃^-(I) and C₁₃H₈N₃O₇^-(J),is sequentially decarboxylated to C₁₂H₉N₃O₄(L) and C₁₂H₉N₃O₅(M).In addition,C₁₃H₈N₃O₅^-(H) might be directly decarboxylated to C₁₂H₉N₃O₃(K),sequentially forming C₁₂H₁₁N₃(C) and C₁₂H₁₂N₂(D).C₆H₆N₂O₂(A),C₆H₄N₂O₄(B),C₆H₈N₂(E),C₆H₆O(F) and C₇H₇NO₃(G) were generated by breaking the —NN— bond of C₁₃H₈N₃O_5.Eventually,the intermediates from Alizarin yellow Rwere photodegraded into CO₂ and H₂O.Using PM3 MOPACcalculations,the net negative charge density of carboxyl(-0.680) was obtained.The —NN—,the C—Cbonds in the benzene ring and the carboxyl group were unstable.The net negative charge density of the benzene ring with carboxyl and nitryl groups were-0.160 and-0.165,respectively,implicating that the dye compound adsorbed on TiO₂ readily reacted with hydroxyl radical.The experimental result was in accordance with the PM3 calculation.The photocatalytic degradation kinetics of Alizarin yellow Ragreed with the Langmuir-Hinshelwood model simulation at pH2.86,catalyst dosage: 1.0 g·L^-1 and radiation intensity: 2350 μW·cm^-2.

• Key words：TiO₂  alizarin yellow R  reaction mechanism  MOPAC  UV-VIS spectra  L-H model

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