自掺杂铋基光催化剂光催化氧化及其单线态氧直接氧化协同降解PPCPs

To efficiently degrade refractory PPCPs such as diclofenac and ibuprofen, a synergistic method is proposed by simultaneously using a visible light photocatalytic oxidation on self-doped Bi-containing photocatalysts and its inducing generation of singlet oxygen. Firstly, highly active self-doped Bi-containing photocatalysts are in-situ or ex-situ fabricated by acidic etching of sodium bismuthate or similar methods. The modified materials show much improved performance in the separation of photo-generated h+/e- pairs and then the photocatalytic ability. Then, the adsorption of PPCPs on the surface of bismuth based photocatalysts is enhanced by strengthening the multiple interactions between the target pollutants and the catalyst surface, including the insertion of an oxygen atom of -COO group in PPCPs molecular into oxygen vacancies, its bridge and configurations with bismuth on the catalyst surface, and the matching effect of a benzene-ring π system in PPCPs molecular with the out-surface of the bismuth based photocatalyst nanosheets. The modified Bi-containing photocatalysts also show a special function of generating singlet oxygen. Therefore, a novel system for the degradation of refractory PPCPs is developed by combining the singlet oxygen oxidation and photocatalytic oxidation. For this purpose, the correlation between PPCPs adsorption behavior and its degradation performance on the surface of bismuth based photocatalysts, and the synergistic effect between the singlet oxygen oxidation and visible light driven photocatalytic oxidation are systematically investigated. GC-MS and HPLC-MS are employed to track PPCPs degradation intermediates to clarify the degradation reaction process and mechanism of PPCPs. Finally, application of the novel method in the treatment of pharmaceutical wastewater is investigated.

常规生物和化学法难以处置布洛芬和双氯芬酸等难降解PPCPs。针对这些PPCPs的分子结构特点，本项目拟原位或异位制备自掺杂铋基光催化剂，改善其可见光响应能力，增强其光催化氧化能力；采用酸解、离子交换等改性方法，增强PPCPs与铋基催化剂之间的相互作用，包括催化剂表面氧空位与污染物分子中氧的作用、铋元素与污染物分子中氧和氮元素的配位作用、二维纳米片催化剂表面与污染物分子中苯环π体系之间的匹配作用，强化催化剂捕集目标污染物的能力；利用所得催化剂自身能产生单线态氧的特殊能力，构筑光催化氧化-直接氧化协同降解新体系。本项目将系统地研究PPCPs在铋基催化剂表面的吸附行为与其降解之间的相互关系、光催化氧化-直接氧化的协同效应，并采用GC-MS和HPLC-MS等手段分析降解过程中的中间产物种类及浓度变化规律，阐明PPCPs协同降解的反应机理，并针对医药废水，探讨新方法在处置PPCPs废水中的应用。

常规生物和化学法难以处置卡马西平等难降解PPCPs。针对这些PPCPs的分子结构特点，本项目采用无机酸原位或异位处理铋酸钠制备自掺杂铋酸钠光催化剂，研究了三价铋自掺杂对其光催化氧化能力的影响；采用酸解、金属离子交换两种改性方法对铋酸钠进行处理制备了亚稳态Bi(III)O6八面体，研究了其释放单线态氧的机理及其对双酚A和诺氟沙星等污染物的高效氧化降解反应原理。最后，构筑了光催化氧化-直接氧化协同降解新体系，研究了光催化氧化-直接氧化在双酚A和卡马西平等污染物降解中的协同效应及其机制。结果发现：（1）当硝酸与铋酸钠的摩尔比不大于0.2时，采用硝酸处理铋酸钠可制备三价铋自掺杂铋酸钠。在可见光条件下，采用此自掺杂铋酸钠光催化剂时，双酚A的零级反应动力学常数为铋酸钠光催化剂的2.6倍；（2）采用无机酸如盐酸处理铋酸钠制备了Bi(III)O6/Bi(V)O6八面体亚稳态结构，增强了其产单线态氧的量和对双酚A等污染物的降解能力。当盐酸与铋酸钠的摩尔比为2时，制备的八面体亚稳态结构直接氧化降解双酚A的反应速率是铋酸钠的42倍；（3）铋酸钠在暗反应条件下可直接氧化降解双酚A，并且双酚A降解速率受反应溶液pH控制。随着反应pH的降低，铋酸钠释放单线态的量及其对双酚A的降解速率成比例增加；（4）变价金属离子如Co2+的共存可增强铋酸钠产单线态氧能力以及对诺氟沙星的降解和矿化能力，并且其产单线态氧的量和对诺氟沙星的降解速率与变价金属离子的氧化还原电位正相关；（5）在可见光光照和酸性条件下，原位实现了三价铋自掺杂铋酸钠同时光催化和单线态氧直接氧化协同降解双酚A；（6）可见光照射显著增强了亚稳态Bi(III)O6八面体释放单线态氧的量，其增强倍数为2.2-3.8，提高对卡马西平的降解和矿化。本项目的研究，不仅提供了一种针对难降解PPCPs的新处理方法，还推动了对金属氧化物晶格氧释放机制和半导体光催化理论的理解。