水相中苯酚光催化降解的全额光子效率

为定量评价光催化反应器的性能,利用主辐射波长为207 nm的KrBr*准分子灯降解水相中的苯酚,测定了光解和光催化降解2种体系中苯酚和TOC去除率,并计算了苯酚降解的ξ_g(全额光子效率),探讨了其影响因素. 结果表明:①延长反应时间、加入适量催化剂、降低初始c(苯酚)能提高苯酚和TOC去除率. 采用动力学模型对苯酚的降解进行拟合,表明光解和光催化降解体系中苯酚的降解均符合准一级动力学模型. ②加入催化剂和提高初始c(苯酚)均可以获得较高的ξ_g,而光源的辐射功率与ξ_g没有线性相关性；在辐射功率为0.76 W、初始c(苯酚)为1.10 mmol/L、催化剂投加量(以ρ计)为0.8 g/L的条件下,ξ_g为5.56%. ③采用高效液相色谱对光催化降解体系中生成的中间产物的变化规律进行研究发现,4种中间产物表现为c(对苯二酚)＞c(邻苯二酚)＞c(对苯醌)＞c(间苯二酚)；通过建立苯酚及中间产物的拟一级降解动力学模型,证实苯酚光催化降解历程为苯酚→芳香烃中间产物→最终产物. 

Analysis of Global Photonic Efficiency of Photolytic Degradation of Phenol in Aqueous Solution

In order to estimate quantitatively properties of photocatalytic reactor, A KrBr* excilamp with main irradiation wavelength of 207 nm was utilized for photolytic degradation of phenol in aqueous solution. Removal efficiency of phenol and TOC in both photolytic and photocatalytic processes were conducted. Global photonic efficiency was calculated and influencing factors were discussed. The experimental results showed that removal efficiency of phenol and TOC were enhanced via prolonging reaction time, adding considerable catalysts as well as lowing initial concentration. Phenol degradations in both photolytic and photocatalytic systems were in good agreement with the pseudo-first order kinetic model based on kinetic model fitting. Higher photonic efficiencies were obtained by adding catalysts or increasing initial concentration of phenol, while there was no obvious linear correlation between global photonic efficiency and irradiation power. The global photonic efficiency was 5.56% when irradiation power, phenol initial concentration and catalyst dosage were 0.76 W, 1.10 mmol/L and 0.8 g/L, respectively. Moreover, the temporal variation trend of intermediates formed was systematically investigated by high performance liquid chromatography. The decreasing concentration of intermediates was:hydroquinone>catechol>benzoquinone>resorcinol. By establishing pseudo first-order kinetic models of phenol and intermediates, we confirmed that the photocatalytic degradation pathway of phenol follows:phenol→aromatic hydrocarbon intermediates→final products.