Ag/AgCl/铁-海泡石异相可见光Fenton催化降解双酚A

光-Fenton技术是高级氧化技术中的一种,常用于难降解废水处理,由于其反应速度快、毒性低、反应条件温和而受到广泛关注.然而,传统的光-Fenton体系具有可见光利用率低、回收困难等缺点.为了解决这些问题,本文采用廉价易得、无污染、吸附能力强的天然矿物海泡石作为催化剂载体,并利用Ag/AgCl能够吸收可见光的表面等离子响应这一光学性质,合成了一种有潜力的非均相等离子体光催化剂Ag/AgCl/铁-海泡石催化剂(Ag/AgCl/Fe-S),并对该催化剂的形貌结构、性能和机理等进行了系统研究.通过XRD,SEM,XPS,BET,UV-vis等表征手段对催化剂形貌、结构和可见光性能进行了分析.其中,XRD和SEM结果显示,Ag/AgCl粒子已经成功负载在Fe-海泡石上;XPS结果显示,铁氧化物的组成主要为FeOOH和Fe2O3;UV-vis结果显示,催化剂有较好的可见光吸收性能.以双酚A为目标污染物,分别考察了Ag/AgCl/Fe-S,Ag/AgCl和Fe-海泡石的光-Fenton催化性能.结果显示,Ag/AgCl/Fe-S降解双酚A的效果明显优于另外两种催化剂,在H2O2浓度为6mmol/L,pH为4,光照强度500W,Ag/AgCl/Fe-S催化剂量为1.0 g/L,双酚A初始浓度为10 mg/L的条件下,1 h时,双酚A基本被完全降解,且3 h时,其矿化率达到61.2%;而Ag/AgCl和Fe-海泡石催化剂在同样的条件下完全降解双酚A至少要3 h,且其矿化率分别只有46.61%和28.85%.另外,还分别探讨了H2O2浓度、pH值、光照强度和催化剂剂量对双酚A降解的影响.最后,通过活性物种捕获、ESR、电化学和PL实验对该体系的反应机理进行了探讨.活性物种捕获实验和ESR实验结果表明,羟基自由基(?OH)和空穴(h+)是该体系中的主要活性物种,且Ag/AgCl/Fe-S+H2O2+vis体系产生的?OH明显多于Fe-S+H2O2+vis体系.为了探讨?OH增多的原因,我们进行了电化学实验和PL实验.电化学实验结果显示,Ag/AgCl/Fe-S催化剂具有更低的阻抗,因此有利于电子-空穴分离.PL结果显示,Ag/AgCl/Fe-S催化剂的电子-空穴复合率更低.结合以上实验,我们提出了Ag/AgCl/Fe-S+H2O2+vis体系对双酚A的降解机理,即一方面催化剂能够发生Fenton反应而产生?OH,另一方面,催化剂中的Ag/AgCl在可见光下由于表面等离子响应而产生电子-空穴,空穴本身可作为活性物种降解双酚A.同时,产生的电子被体系中的Fe3+捕获生成Fe2+,从而促进了铁循环,有利于体系中产生更多的?OH.最后,空穴和羟基自由基发生协同作用共同促进污染物降解.

Synthesis of Ag/AgCl/Fe-S plasmonic catalyst for bisphenol A degradation in heterogeneous photo-Fenton system under visible light irradiation

A novel plasmonic photo-Fenton catalyst of Ag/AgCl/Fe-S was synthesized by ion exchange and photoreduction methods. The obtained catalyst was characterized by X-ray diffraction, X-ray photo-electron spectroscopy, scanning electron microscope imaging, and Brunauer-Emmett-Teller meas-urements. Moreover, the photocatalytic activity of Ag/AgCl/Fe-S was investigated for its degrada-tion activity towards bisphenol A (BPA) as target pollutant under visible light irradiation. The ef-fects of H2O2 concentration, pH value, illumination intensity, and catalyst dosage on BPA degrada-tion were examined. Our results indicated that the Ag/AgCl material was successfully loaded onto Fe-sepiolite and showed a high photocatalytic activity under illumination by visible light. Further-more, active species capture experiments were performed to explore the photocatalytic mechanism of the Ag/AgCl/Fe-S in this heterogeneous photo-Fenton process, where the major active species included hydroxyl radicals (?OH) and holes (h+).