复杂卤氧化铋纳米材料调控制备及其光催化处理页岩气返排废液研究

Recently, large-scale development of shale gas produced a large number of flowback waste liquor. A large number of polymers contaminant in above wastewater cannot be removed using conventional method to meet the emission requirements. It has become one of the main bottlenecks for shale gas development. Therefore, we should develop some new materials for flowback waste liquor treatment. In this project, we plan to adjust the atomic ratio of Bi/O/X in Bi-O-X semiconductor materials, and prepared complex Bi-O-X photocatalytic materials with higher stabilization, better bulk properties and surface properties than BiOX. By tuning the exposure facets, thickness two-dimensional crystal, and the solid solution, the stabilization, bulk properties and surface properties of complex Bi-O-X can be optimized. And then, the performance of photocatalytic flowback waste liquor degradation can be enhanced. Finally, the band structure of complex Bi-O-X was analysed by density functional theory (DFT) calculation. And the photocatalytic mechanism of complex Bi-O-X was studied by surface chemical analysis, instrument characterization and transition state theory, molecular dynamics calculation. The results of this study provide a new way for the treatment of refractory polymer in flowback waste liquor, and provide a theoretical and technical support for the photocatalytic flowback waste liquor treatment.

近年来，页岩气大规模开发产生了大量的压裂返排废液，该废液中存在大量聚合物，利用常规方法难以处理使之达到排放要求，已成为制约我国页岩气开发的主要瓶颈之一，研发治理页岩气返排废液材料迫在眉睫。本项目通过调整卤氧铋半导体材料中各元素比例制备稳定的复杂Bi-O-X光催化材料，并调控其暴露晶面、二维晶体厚度和固溶体改良复杂Bi-O-X光催化材料，增强复杂Bi-O-X材料光催化降解压裂返排废液中聚合物（胍胶为模型）的性能。结合密度泛函(DFT)理论计算，分析复杂Bi-O-X的能带结构的变化；结合表面化学分析仪器表征和过渡态理论、分子动力学理论计算，分析复杂Bi-O-X的缺陷类型、吸附性能，进而研究其光催化作用机理。该研究成果为压裂返排废液中难降解的聚合物处理提供了一个新的思路，并为光催化处理压裂返排废液提供了理论和技术支撑。

水力压裂是当前油气田增产作业领域应用最为广泛的手段之一。当压裂作业完成后，从地层返排出来的压裂返排液成分十分复杂，它具有高化学需氧量（COD）、高黏度、高稳定性等特点。在压裂返排液处理过程中，复杂有机成分的去除一直是难点。光催化技术因其对有机污染物的降解具有无选择性、无二次污染等特点而被广泛关注。因此，本项目拟将光催化技术引入压裂返排液中有机聚合物处理领域，为压裂返排液的处理提供一种新思路。光催化技术的核心是高效光催化剂，而当前光催化技术领域的研究热点之一就是具有高效性能的可见光响应卤化氧铋基光催化剂（BiOX，X = Br，Cl和I）的制备及其光催化机理探究。本文主要的研究目标是首先探究两种当前应用最为广泛的改性手段—固溶结构和复合结构BiOX（X = Br，I）光催化剂的光催化机理，并以此为根据自合成一系列改性卤化氧铋基光催化剂，通过有机污染物降解对其光催化降解性能进行评价并进行降解机理探究，再将自合成的光催化剂应用到压裂返排液的主要成分—羟丙基瓜胶以及有机硼交联剂的光催化降解并进行效果评价，最后直接将优选出的性能优异的光催化剂应用到光催化处理油田产出压裂返排液。