| Sulfate radical(SO4-·) based advanced oxidation processes(AOPs) have a promising prospect in the field of waswater treatment and soil remediation due to its strong oxidizing and mineralization ability, wide application scope and endurability to inorganic salts. However, there are two problems need to solve for popularization and application of this technology. Firstly, there are lack of universal and authoritative explanations of SO4-· production and free radical transfer chain. Secondly, further investigation have been paied to develop highly efficient activation technologys and catalysts of persulfate and peroxymonosulfate(PMS). In this work, base on special crystal structure of layerd double hydroxide/layered double oxide(LDH/LDO) and subtle electron properties of CNTs, the Co Mn Al-LDH/LDO and CNTs-LDH/LDO with ultrastrong catalytic performace were fabricated and applied to activate PMS for endocrine disruptors BPA degradation. The preparation and characterization of materials, optimum technological condition, activation and degradation mechanism were investigated by modern spectosopy, micro-beam and micro-zone technology and degradation experiments. The obtained achevements and results are as follows:(1) Co Mn Al-LDH/LDO were fabricated by different methods, i.e. co-precipitation, static urea hydrolysis and dynamic urea hydrolysis. The results of SEM, FTIR and N2 adsorption-desorption indicated that morphology, BET and pore structure of materials prepared by different preparation methods were different. The adsorption rates of BPA by LDO is less that 20%, while BPA degradation is excellent by LDO activate PMS. Besides, LDO exhibited a higher catalytic activity than other metal oxides(including Co Al-LDO, Co3O4, Mn3O4 and Mn O2) due to its highly dispersed catalytic sites.(2) Further investigation indicated that BPA degradation rate was affected by p H, temperature. the LDO/PMS system was very suitable for the treatment of neutral or alkaline wastewater. the degradation could be well described by the first order kinetics with the activation energy of 76.83 k J·mol-1. Based on the identification of intermediate products by LC-MS and GC-MS, the degradation pathway of BPA was proposed, in which mainly involved hydroxylation to form hydroxyl-BPA and cleavage of benzene-rings. The mechanism of heterogeneous catalysis involves three one-electron transfer processes: Co2+/Co3+, Mn3+/Mn4+ and Co3+/Mn3+. The sulfate radicals were recognized as the main species to oxidize pollutants in the LDO/PMS system.(3) A 3D hierarchical honeycomb nano-structured o-MWCNTs coupled with Co Mn Al-layer double oxides has been successfully fabricated. The role of MWCNTs was investigated and discussed in terms of surface morphology, structure, composition and catalytic activity of the as-prepared nanohybrid by investigation of SEM, TEM, XRD, XPS, Ranman et al.. The results showed that catalytic performance of the CNTs-LDO can be significantly enhanced with the increase of o-MWCNTs contents in the hybrids, and MWCNTs provided an orientation/confinement for nanohybrid formation and the defect generated by calcination might increase PMS activation for the production of sulfate radicals.(4) o-MWCNTs with different dimater(i.e., less than 8 nm, 30-50 nm and more than 50 nm) were used as raw metrials for CNTs-LDH/LDO fabrication. The results of characterization indicated that morphology, crystal structure and composition of CNTs-LDH/LDO were effected by dimater of CNTs and surface functional groups. The catalytic performance was reduced with increase of dimater.The above obtained conclusions in this study enrich the theory system of SO4-· based AOPs, and provide the experimental basis for the application of layer doubole compounds in environmental management and treatment of BPA. |
