Enhancement of UV-assisted TiO2 degradation of ibuprofen using Fenton hybrid process at circumneutral pH

Abstract

A synergistic UV/TiO2/Fenton (PCF) process is investigated for the degradation of ibuprofen (IBP) at circumneutral pH. The IBP decay in the PCF process is much faster than that with the conventional UV, UV/H2O2, Fenton, photo-Fenton, and photocatalysis processes. The kinetics analysis showed that the IBP decay follows a two-stage pseudo-first order profile, that is, a fast IBP decay (k1) followed by a slow decay (k2). The effects of various parameters, including initial pH level, dosage of Fenton's reagent and TiO2, wavelength of UV irradiation, and initial IBP concentration, are evaluated. The optimum pH level, [Fe2+]0, [Fe2+]0/[H2O2]0 molar ratio, and [TiO2]0 are determined to be approximately 4.22, 0.20 mmol/L, 1/40, and 1.0 g/L, respectively. The IBP decay at circumneutral pH (i.e., 6.0–8.0 for wastewater) shows the same IBP decay efficiency as that at the optimum pH of 4.22 after 30 min, which suggests that the PCF process is applicable for the treatment of wastewater in the circumneutral pH range. The lnk1 and lnk2 are observed to be linearly correlated to 1/pH0, [IBP]0, [H2O2]0, [H2O2]0/[Fe2+]0 and ln[TiO2]0. Mathematical models are therefore derived to predict the IBP decay. 药品及个人护理品（PPCPs）造成的潜在环境污染已引起广泛关注.布洛芬（IBP,2-（4-异丁基苯基）丙酸）作为苯丙酸类非甾体抗炎药物,是一种在水环境中广泛检测到的PPCPs类物质.水环境中的IBP主要来自制药企业排放和人体代谢物,因IBP具有不易挥发、物理性质稳定、半衰期较长和不易被生物吸收等特点,其在环境的残留浓度较高且污染风险大.目前,传统的水处理工艺并不能有效治理水中的IBP,比如:混凝剂和絮凝剂对IBP的去除效率低,吸附和膜处理运行成本过高且不能矿化IBP.近年兴起的光催化技术利用OH和O2儃等强氧化性活性物种降解水中有机污染物,将其彻底矿化,实现污染物的无害处理.光催化技术适用于常温、常压和中性pH环境,该环境特点与污水环境十分匹配,适合应用.但异质光催化通常发生在催化剂表面,有效反应活性位少,反应速率不够高.相比而言,同质芬顿反应能够均匀、快速地在整个溶液中发生反应,但芬顿反应必须在酸性条件下才可以进行.本文整合了异相光催化和均相光-芬顿反应的优点,设计了紫外/TiO2/芬顿（PCF）复合工艺,评估了在中性pH下对典型的PPCPs布洛芬的降解效果.对比实验结果表明,PCF复合工艺对IBP的降解速率比传统的UV,UV/H2O2,Fenton,光-Fenton和光催化快得多.动力学分析发现,IBP的降解遵循两阶段的一级反应动力学,且速率常数k1>k2.本研究进一步优化了运行参数,确定IBP降解的最佳条件为:pH=4.2,[Fe2+]0=0.20 mmol/L,[Fe2+]0/[H2O2]0=1/40,[TiO2]0=1.0 g/L.pH值的增加造成IBP降解速率略微降低,但在30 min反应时间内,中性pH（6.0–8.0）与最佳pH条件下的降解效率完全相同,证明PCF在中性pH下进行水处理切实可行.数据分析发现,lnk1和lnk2均与1/pH0,[IBP]0,[H2O2]0,[H2O2]0/[Fe2+]0和ln[TiO2]0线性相关,据此建立了IBP去除效率的数学预测模型,通过验证发现,动力学模型曲线与实验数据高度契合,表明模型的有效性高.