本论文以2,4,5-三氯苯氧基乙酸（2,4,5-T）降解率、氯离子生成浓度、辐照后剩余2,4,5-T的浓度以及其它降解产物为指标，首次采用60Co-γ辐照法研究2,4,5-T水溶液中2,4,5-T的辐射降解，计算了2,4,5-T降解速度与分子中C-Cl键的热力学关系，并比较了60Co-γ直接辐照法、H2O2/γ结合法、O3/γ结合法以及TiO2/γ结合法降解2,4,5-T的效果。 在直接辐照法的实验中，研究了吸收剂量、2,4,5-T初始浓度、溶液酸碱度、辐照气氛等对2,4,5-T辐射降解的影响。发现：辐照空气饱和的2,4,5-T水溶液，随着吸收剂量的增大，2,4,5-T浓度逐渐降低，降解率不断增加，当吸收剂量为3.2kGy时，2,4,5-T完全降解；溶液中生成的氯离子浓度随吸收剂量的增加而增大，到一定剂量后增长变缓，在吸收剂量为12.8kGy时产生的氯离子浓度为5.09×10-4mol/L；质谱图分析表明2,4,5-T降解过程中可能会生成2-羟基-4,5-二氯苯氧基乙酸、2,4,5-三氯酚、4,6-二氯间苯二酚和二氯酚等物质。在相同吸收剂量下，2,4,5-T初始浓度越低，2,4,5-T的降解率越高。相同浓度的2,4,5-T水溶液，溶液初始pH对2,4,5-T的降解率影响不大。辐照N2饱和的含有2,4,5-T和特丁醇的中性水溶液与N2O饱和的2,4,5-T中性水溶液，发现，N2O饱和条件下的降解率明显大于N2饱和含有特丁醇条件下的值，而两种体系得到的氯离子浓度相差不大；在0～0.8kGy吸收剂量范围，2,4,5-T和氯离子浓度的对数与吸收剂量之间具有良好线性关系。在O2饱和条件下，吸收剂量为1.6kGy时降解率已达100%；当吸收剂量为12.8kGy时，产生的氯离子浓度为5.35×10-4mol/L，高于空气饱和条件得到的结果。利用量子化学方法计算了2,4,5-T分子的一些热力学参数，包括分子中各化学键的键长以及断开C-Cl键时所需要的能量，比较了这些热力学参数与2,4,5-T分子降解脱氯速度的关系。其中，各C-Cl键键长按照2位＜1位＜5位的顺序增加，其数值依次为1.7442、1.7445、1.7486；而断裂这三种C-Cl键所需要的能量则是按照5位＜2位＜1位的顺序依次增加，分别为366.2275kJ/mol、378.8671kJ/mol、378.9722kJ/mol。以H2O2/γ结合法、O3/γ结合法和TiO2/γ结合法辐射降解溶液中的2,4,5-T，并将这三种方法得到的2,4,5-T的降解率和氯离子浓度与直接辐照法得到的结果相比较，发现γ辐射法与其它氧化法结合得到的2,4,5-T降解率以及氯离子浓度都高于直接辐照法。三种方法均在1.6kGy吸收剂量时实现2,4,5-T完全降解，而单独辐照法达到2,4,5-T的完全降解需3.2kGy；当吸收剂量达到12.8kGy时，H2O2/γ结合法、O3/γ结合法和TiO2/γ结合法得到的氯离子浓度分别为5.21×10-4mol/L、5.84×10-4mol/L和5.95×10-4mol/L，均高于直接辐照法得到的氯离子浓度（5.09×10-4mol/L）。说明γ辐射法与其它氧化法结合可以取得较好的去除效果，且从脱氯角度来讲O3/γ结合法和TiO2/γ结合法对于2,4,5-T的降解效果优于H2O2/γ结合法的效果。

In this paper, the 60Co-γ irradiation degradation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in aqueous solutions was investigated for the first time. The degradation rate of 2,4,5-T, the concentration of Cl-, the remained concentration of 2,4,5-T and other irradiation products were used as the analytical index. The relationships between the degradation rate of 2,4,5-T and the thermodynamics parameters of C-Cl were calculated by the method of quantum chemistry. The degradation effects of γ irradiation, H2O2/γ, O3/γ and TiO2/γ were compared. In the experiment of direct γ irradiation of 2,4,5-T aqueous solution, the effects of absorbed dose, the initial concentration of 2,4,5-T, initial pH of the solution, and the atmosphere on the degradation of 2,4,5-T were studied. The results showed that the concentration of 2,4,5-T decreased with the dosage, and so as the degradation rate increased. When the dosage was 3.2kGy, 2,4,5-T was completely degraded. The concentration of Cl- increased gradually with the dosage, and then the rising trend slowed down after a certain dosage. When the dosage was 12.8kGy, the concentration of Cl- was 5.09×10-4mol/L. LC-MS analysis showed the probable degradation products of 2,4,5-T irradiation were 2-hydroxy-4,5-dichlorophenoxyacetic acid, 2,4,5-trichlorophenol, 4,6-dicholoresorcinol and dichlorophenol. The initial concentration of 2,4,5-T had obvious effects on the degradation. The lower the initial concentration was, the higher the degradation rate of 2,4,5-T was. The initial pH of the solution affected little to the degradation rate of 2,4,5-T. Comparing the results obtained from the N2 saturated neutral aqueous solution containing 2,4,5-T and t-BuOH with the N2O saturated solution containing 2,4,5-T, it was found that in the both systems, the degradation rate of 2,4,5-T and the concentration of Cl- increased with the increase of absorbed dose. However, the degradation rate of 2,4,5-T gained from the former system was higher than that gained from the latter system, and the concentration of Cl- in these two systems were almost the same. We also found that the logarithm of the concentration of 2,4,5-T and Cl- increased linearly with the dosage in the range from 0 to 0.8kGy. The degradation rate of 2,4,5-T in the solution saturated with O2 was more favorable than that in air-saturated solution. For the O2 saturated solution, the degradation rate of 2,4,5-T reached 100% when the dosage was 1.6kGy, and the concentration of Cl- was 5.35×10-4mol/L when the dosage was 12.8kGy. Both values were higher than those in the case of air saturation.Some thermodynamics parameters including the length of chemical bonds in the molecule of 2,4,5-T and the energy of breaking down the C-Cl bonds were calculated by the method of quantum chemistry. The lengths of C-Cl increased in the order of the position of Cl atoms (2＜1＜5), and the numerical value were 1.7442, 1.7445, 1.7486 respectively. The energy of breaking down the C-Cl bonds increased in the order of the position of Cl atoms (5＜2＜1), and the numerical value were 366.2275kJ/mol, 378.8671kJ/mol, 378.9722kJ/mol respectively. Compared the degradation effects (including the degradation rate of 2,4,5-T and the concentration of Cl-) of γ irradiation, H2O2/γ, O3/γ and TiO2/γ, it was found that the methods of γ irradiation combined with other oxidation methods could achieve better degradation effects than that in the method of γ direct irradiation. In the methods of γ irradiation, 2,4,5-T was completely degraded when the dosage was 3.2kGy, but in the methods of H2O2/γ, O3/γ and TiO2/γ, the complete degradation could be achieved when the dosage was 1.6kGy. When the dosage was 12.8kGy, the concentration of Cl- were 5.21×10-4mol/L, 5.84×10-4mol/L and 5.95×10-4mol/L respectively in the three combined methods. We therefore concluded that the combined methods of TiO2/γ, O3/γ and H2O2/γ could achieve better degradation effects compared with direct γ irradiation method. From the aspect of dechlorination, the methods of O3/γ and TiO2/γ could achieve better degradation effects than that by the method of H2O2/γ.