CoCuAl-LDOs As Heterogeneous Catalyst Activating PMS For Degradation Of Organic Pollutants: Performance And Mechanism Study

In order to develop heterogeneous catalytic material with high performance toward activating PMS for the degradation of organic pollutants in wastewater,in this dissertation,CoCuAl-LDOs was prepared through the calcination of the precursor CoCuAl-LDHs.The catalytic activity of CoCuAl-LDOs was evaluated via the degradation of acid orange 7（AO7）in CoCuAl-LDOs/PMS system.The influence of synthesis conditions and degradation parameters on the degradation efficiency of AO7was investigated.The catalytic mechanism and the degradation pathway of AO7 in CoCuAl-LDOs/PMS system were also studied.Characterization methods such as XRD,SEM and BET were used to study the crystalline structure,morphology and specific surface area of the prepared catalyst.It was found that CoCuAl-LDOs is solid solution of spinel oxidate with high specific surface area.Preparation conditions such as aging time,aging temperature,Co:Cu:Al molar ratio and calcination temperature have influence on the crystallinity,composition and specific surface area of the catalyst,further affecting its catalytic activity.CoCuAl-LDOs/PMS system possessed strong capability of degrading organic pollutants.5 mg of AO7 can be completely degraded within 30 min using 0.1 g/L catalyst and 0.1 g/L PMS.Kinetic study revealed that the degradation efficiency can be influenced by the loading of catalyst and PMS,reaction temperature,solution p H and co-existing anions.Moreover,the study on the catalyst reusability demonstrated that CoCuAl-LDOs possessed high stability.Sulfate radical and hydroxyl radical were identified as the active species responsible for degrading organic pollutants in CoCuAl-LDOs/PMS system through EPR and radical quenching experiment.The mechanism of CoCuAl-LDOs catalyzing PMS was uncovered through the surface study of the catalyst before and after reaction,which indicated the redox cycle of Co²⁺/Co³⁺and Cu²⁺/Cu³⁺played an important role in the activation process.Compared to Co Al-LDOs and Cu Al-LDOs,CoCuAl-LDOs exhibited much higher catalytic activity due to the Co-Cu synergistic effect which can facilitate the redox cycle of Co²⁺/Co³⁺and Cu²⁺/Co³⁺.Additionally,the formation of single phase containing both Co and Cu was found to be important for Co-Cu synergistic effect in terms of catalyzing PMS.Degradation pathway of AO7 in CoCuAl-LDOs/PMS system was investigated based on the degradation intermediates detected and theoretical calculation.