Abstract：
The radiolytic degradation of 4-hydroxybenzoate (4-HBA-) in aerated, oxygen-free and N2O-saturated aqueous solutions at concentrations of 0.10 and 0.25 mmol/dm3 were gamma irradiated at different doses in a source of Co-60. The results show that ·OH adds predominantly to the 3 position of the aromatic ring, and elimination of the acid group leads to the degradation of 4-HBA-. With an N2O-saturated 0.10 mmol/dm3 4-HBA- solution, total degradation occurred at 1.6 kGy, and with a 0.25 mmol/dm3 solution, total degradation occurred at 3.5 kGy. In the aerated and oxygen-free 0.25 mmol/dm3 4-HBA- solutions, the behavior was similar, degradation occurring at a dose of 13.1 kGy. At the concentration of 0.10 mmol/dm3, total degradation occurred at 7.0 kGy, with small amounts of radiolytic products and byproducts. We propose a mechanism for the degradation of 4-HBA- caused by water radicals produced in the three environments, leading to formation of the identified stable products. Oxidation was followed by chemical oxygen demand (COD), which decreased as the 4-HBA- concentration increased. The kinetics showed a pseudo-first-order behavior. The rate constant of degradation was similar for the solutions with and without oxygen.
摘要：
4-羟基苯甲酸酯（4-HBA-）在充气中的放射性降解，在Co-60源中以不同剂量对浓度为0.10和0.25mmol/dm3的无氧和N2O饱和水溶液进行γ辐照。结果表明，·OH主要添加到芳香环的3位，酸基团的消除导致4-HBA-的降解。使用N2O饱和的0.10mmol/dm34-HBA-溶液，总降解发生在1.6kGy，和0.25mmol/dm3溶液，总降解发生在3.5kGy。在充气和无氧0.25mmol/dm34-HBA-溶液中，行为是相似的，降解发生在13.1kGy的剂量。在0.10mmol/dm3的浓度下，总降解发生在7.0kGy，有少量的放射性分解产物和副产物。我们提出了在三种环境中产生的水自由基引起的4-HBA-降解的机制，导致形成确定的稳定产品。氧化后是化学需氧量（COD），随着4-HBA-浓度的增加而降低。动力学表现出伪一阶行为。对于有和没有氧气的溶液，降解的速率常数相似。
