光催化微反应器中水样光催化降解及Cd^(2+)在线检测

Photocatalytic Degradation of Water Sample and On-line Monitoring of Cd^(2+) in Microreactor

本文以粉末法制备TiO_2涂层的玻璃微流控芯片作为光催化反应器,采用UV-LED点光源为紫外光源,实现了水样中EDTA的光催化降解,并用铋膜电极差分脉冲溶出伏安法在线检测微量水样中的重金属离子Cd^(2+)。水样中的Cd^(2+)由于EDTA的络合作用无法在铋膜电极上产生电流信号,而当水样在光催化微反应器中经紫外光催化后,由于EDTA与Cd^(2+)的配合物结构遭破坏,因此释放出游离的Cd^(2+),从而使Cd^(2+)的电流信号得到一定程度的恢复。Cd^(2+)的电流恢复程度越大,表明EDTA被光催化降解的程度越高。本文考察了光照强度、反应液流速和氧气流速、pH等因素对EDTA光催化降解效率的影响。在光照强度为120mW/cm^2、反应液流速为50μL/h、氧气流速为850μL/h、pH为4.4条件下,水样中EDTA的光催化降解率效果最佳,水样中Cd^(2+)的电流恢复程度可达92.6%。反应液流速为300μL/h时,Cd^(2+)的电流恢复率为60.0%,重复光催化反应5次的RSD为5.2%,具有较好的重现性。本文建立了水样EDTA光催化降解及Cd^(2+)在线检测的微分析系统,在线检测所需的样品体积仅为0.3mL,完成一个水样分析的时间约为60min。

In this paper,a micro-analysis system integrated pretreatment of water sample by photocatalysis of organic matter with on-line monitoring of Cd-（2＋）is established. Aphotocatalytic microreactor based on microfluidic chip coated with TiO2 filmhas been fabricated and integrated with electrochemical detection system.The Cd-EDTA complex served as model system to demonstrate the on-line photocatalytic degradation of organic matter followed by the differential pulse stripping voltammetric determination of the metal ion in aqueous solution.The voltammetric signal of 0.1mg/L Cd^2＋in acetate buffer（pH 4.4）at the Bismuth Film Electrode is suppressed by EDTA.While irradiating the TiO2-coated microfluidic chip with UV-LED at 365 nm causes the recovery of the Cd^2＋signal,indicating the photocatalyticdegradation of EDTA.The effects of UV light intensity,flow rate,flow rate of oxygen and other factors on the photocatalytic degradation efficiency have been studied.Under the optimal condition of light intensity being 120mW/cm^2,pH 4.4,flow rate of oxygen being850μL/h and the flow rate of water sample being 50μL/h,the recovery of the Cd^2＋signal rate up to 92.6%.When the flow rate of water sample is 300μL/h,the recovery of the Cd^2＋signal is 60.0%,and the RSD of the recovery of the Cd^2＋signal is 5.2%.The sample volume needed for the electrochemical detection of Cd^2＋is only0.3mL.The total analysis time for one measurement is about 60 min.