UV/NaClO和UV/过碳酸钠工艺降解水杨酸的对比

Comparison of UV/NaClO and UV/Sodium percarbonate processes for degradation of salicylic acid

采用UV/NaClO和UV/过碳酸钠(SPC)工艺降解水中水杨酸(SA),对比考察了氧化剂种类和投加量对SA去除的影响,采用淬灭法和电子顺磁共振波谱仪(EPR)鉴定识别了2种工艺中的自由基,通过竞争动力学的方法计算了SA与•OH、CO_(3)^(•-)的二级反应速率常数及反应体系中不同组分的贡献,从环境水样模拟、急性毒性和经济效益等角度比较了SA的去除效果.结果表明,UV/NaClO工艺和UV/SPC工艺降解SA的拟一级动力学常数分别为0.4378,0.3794min^(-1).UV/NaClO和UV/SPC体系中分别存在•OH、Cl•和O_(2)^(•-)、•OH及CO_(3)^(•-)等自由基.SA与•OH、CO_(3)^(•-)的二级反应速率常数分别为3.97×10^(9),8×10^(7)L/(mol⋅s).UV/NaClO工艺中活性氯自由基(RCS)(79.91%)对SA去除起主导作用;而UV/SPC工艺中O_(2)^(•-)(51.75%)与•OH(41.42%)起主导作用.环境水样中SA在UV/NaClO和UV/SPC工艺中的降解受到抑制,其反应速率分别平均降低了67%和74%.UV/SPC工艺反应溶液的抑制率(25%)较UV/NaClO工艺反应溶液(63%)低38%.SA降解率达到97.5%以上时UV/SPC工艺的成本[37.1$/(m^(3)⋅order)]是UV/NaClO工艺成本[4.0$/(m^(3)⋅order)]的9.3倍,UV/NaClO工艺较UV/SPC工艺具有较高的经济效益.

The degradation of salicylic acid(SA)in aqueous solution by UV/NaClO and UV/SPC processes was investigated.The effects of oxidizer types and dosage on SA removal were compared.The free radicals in the two processes were identified by quenching method and electron paramagnetic resonance(EPR)spectroscopy.The second-order rate constants of•OH and CO_(3)^(•-)with SA and the contributions of different components in the reaction system were determined by competitive kinetics.The removal of SA was compared in terms of environmental water samples simulation,acute toxicity and economic benefit.The pseudo-first-order kinetic rate constants of UV/NaClO and UV/SPC processes were 0.4378 and 0.3794min^(-1),respectively.•OH and Cl•were detected in UV/NaClO process,while O_(2)^(•-),•OH and CO_(3)^(•-)were detected in UV/SPC process.The second-order rate constants of•OH and CO_(3)^(•-)with SA were calculated to be 3.97×10^(9) and 8×10^(7)L/(mol⋅s),respectively.Reactive chlorine species(RCS)(79.91%)functioned a dominant role in the removal of SA in UV/NaClO process,while O_(2)^(•-)(51.75%)and•OH(41.42%)functioned a dominant role in UV/SPC process.The degradation of SA in environmental water samples by UV/NaClO and UV/SPC processes was inhibited,and the removal rates were reduced by 67%and 74%,respectively.The inhibition rate of UV/SPC process(25%)was 38%lower than that of UV/NaClO process(63%).The cost of UV/SPC process[37.1$/(m^(3)⋅order)]was 9.3 times higher than that of UV/NaClO process[4.0$/(m^(3)⋅order)]when SA degradation rate was above 97.5%.UV/NaClO process had higher economic benefit than UV/SPC process.