“呼吸式”富集PAHs光阳极的制备及其光电催化降解土壤淋洗废水的过程机理研究

Soil washing is one of the effective technology for PAHs contaminated soil remediation, which accomplish in eluting contaminants in soil by solubilization of the eluent. However, the resulting soil-washing effluent cannot be treated efficiently as micelles hinder contaminants from contact with free radicals. Based on this bottleneck, a composite photoelectrode (CA/TiO2/Gy) with ability to accumulate organic pollutants in “Imitated respiratory” mode has been designed and fabricated in this program. The composite photoelectrode has the ability to complete the process of "absorbing micelles containing organic pollutants—destabilizing micelles and stripping pollutants—exhaling pollutants free micelles", thus breaking the hindrance of the micelles to the degradation of pollutants in soil-washing effluent. Besides, Gy with gradually increasing distribution in the composite photoelectrode could suppress recombination of electron-hole, so as to synergetic promoting the photoelectrocatalytic degradation efficiency of PAHs soil-washing effluent. This program focused on studying influence of process parameters on physical, chemical, optical and electrochemical properties of materials, and associating properties of the micelle directional absorption, PAHs stripping, and free micelle desorption with microstructure and hydrophilicity of material and external bias, in order to propose the mechanism of “Imitated respiratory” accumulating mode. And exploring mechanism of Gy distribution on reducing electron-hole recombination. The mechanism and degradation products of photoelectrocatalytic degradation of PAHs soil-washing effluent by using the composite photoelectrode was elucidated, and the recovery of the treated effluent would also study. This program would provides a theoretical basis for utilizing CA/TiO2/Gy composite photoelectrode on photoelectrocatalytic degradation of soil-washing effluent.

土壤淋洗技术是治理PAHs污染土壤的最有效手段之一，污染物在淋洗剂增溶作用下高效洗脱，但产生的淋洗废水因胶束阻碍无法高效处理。基于上述瓶颈问题，本项目拟设计“呼吸式”富集PAHs复合光阳极（碳气凝胶/二氧化钛/石墨炔，CA/TiO2/Gy），其可于变化偏压下实现“吸收胶束—剥离污染物—呼出空胶束”，打破胶束阻碍，且逐层递进分布的Gy进抑制e-—h+复合，协同提升光电催化降解效率。重点研究复合光阳极制备工艺参数对材料物化性质、光学性质、电化学性质等影响规律，关联材料微观结构、亲疏水性、外加偏压等对胶束定向吸收、PAHs剥离、空胶束脱附的性能关系，揭示PAHs富集微观过程机制，提出“呼吸式”PAHs富集机理；并探索Gy分布对抑制e--h+复合的作用机制；明确复合光电极对PAHs土壤淋洗废水的光电催化降解机理及影响因素，确定降解产物及淋洗废水循环利用性能，为光电催化降解淋洗废水技术提供理论依据。

土壤淋洗技术是治理PAHs污染土壤的最有效手段之一，污染物在淋洗剂增溶作用下高效洗脱，但产生的淋洗废水因胶束阻碍无法高效处理。基于上述瓶颈问题，本项目设计并制备多类复合材料，应用于制作复合光阳极，用以在光照和交变偏压下进行“呼吸式”光电催化降解増溶PAHs。首先对淋洗剂増溶PAHs的规律进行了研究与表征；在设计“呼吸式”光电催化降解増溶PAHs模型的基础上，制备了CA/TiO2和CA/ZnTiO3-TiO2（R）等复合材料，其具备对増溶PHE的富集的催化降解能力；结合以上结果，设计并制备了复合光阳极，并应用于“呼吸式”光电催化降解増溶PHE，对其微观机理进行分析，并对回用性能进行研究；以CNTs、Gy和Ge等碳材料掺杂TiO2纳米颗粒制备光阳极，并对其研究其“呼吸式”光电催化降解性能。通过以上内容研究可得到以下结论，通过对表面活性剂増溶PAHs性能的研究，确定増溶PAHs浓度表达方式，并对“呼吸式”光电催化降解过程进行设计；对CA/TiO2复合材料进行制备，确定了该体系内纳米TiO2的重要作用，并推测其富集降解増溶PHE的性能及机理；在此基础上，制备了CA/ZnTiO3-TiO2（R）复合材料，进一步提升了其富集降解増溶PHE的能力，其比表面积可达1215.92m2/g，对増溶PHE的移除效率可达91.7%；设计并制备复合光阳极，并将之用于“呼吸式”光电催化降解増溶PHE，在10Hz交变外加偏压条件下，増溶PHE的光电催化降解效率可达90.42%，相较恒压光电催化降解有较大提升。本项目研究结果具备科学意义和应用价值，在胶体与界面化学领域，进一步明确了増溶体系内固-液界面上，被増溶物质与表面活性剂的吸附与转移过程，及其固-液界面的孔结构参数对其转移过程的影响，同时验证了外界电场影响下，胶束及増溶有机物在固-液界面电极上的富集机制，为相关领域研究提供参考和依据；在环境领域应用中，证实了“呼吸式”光电催化法处理増溶有机废水的可行性，为土壤淋洗废水的处理提供新方案与思路，并对后续相关研究起到支撑和参考作用。