Study On Ferromagnetic Sludge-based Activated Carbon Preparation And Its Application In Catalytic Ozonation Of P-CBA

In order to solve the separation problem of powdered sludge-based activated carbon(SAC),a series of novel ferromagnetic sludge-based activated carbons(FMSACs)with a good magnetic separation ability were prepared through co-precipitation method in this study.The structure and physio-chemical properties of FMSACs and their catalytic ozonation performance on the removal of p-chlorobenzoic(p-CBA)were investigated.The influence factors and catalytic mechanism of p-CBA removal during FMSACs catalytic ozonation process were also studied.The result of specific surface area and pore size distribution(BET)analysis showed that compared with SAC,the specific surface areas of FMSACs were not significantly changed.And with the ferromagnetic material loaded,the average pore size of SAC increased.The X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)analysis showed that the loading of ferromagnetic material on SAC did not break the pore structure and surface characteristics of SAC.In contrast,with the ferromagnetic material loaded,the content of surface metal components increased,which further enhanced the catalytic properties of SAC.The magnetic properties analysis by the vibrating sample magnetometer(VSM)showed that FMSACs have good magnetic separation performance and can be quickly separated by a magnet.The results of the p-CBA removal experiment during FMSACs catalytic ozonation process showed that the removal rate of p-CBA increased as the iron contents on FMSACs increased to 2.3 wt%,and began to decrease with the further increase of the iron contents from 2.3(removal rate:80%)to 9.5 wt%(removal rate:64%).The highest p-CBA removal rate(80%)was achieved in 2.3wt%-FMSAC catalytic ozonation process.Studies had already acknowledged that the agglomeration of excess iron oxide on the FMSACs surface decreased the density of active sites and distorted the regular structure of catalyst,thus,weakened FMSACs catalytic performance.The influence factor of p-CBA removal during FMSACs catalytic ozonation process were also investigated in this study,the optimum experimental condition was determined to be:1 mg/L of ozone concentration,40 mg/L of 2.3wt%-FMSAC catalyst dosage and 1 mg/L of the initial concentration of p-CBA.The reusability experiment result showed that after six repetitive runs of 2.3wt%-FMSAC catalytic ozonation,the removal rate of p-CBA only decreased slightly.The prepared novel FMSACs had perfect catalytic efficiency and good reusability in catalytic ozonation process.The result of the tert-butanol inhibition test showed that the hydroxyl radical played a major role in FMSAC catalytic ozonation process.By comparing the removal performance of p-CBA in different modified FMSACs catalytic ozonation process,it was found that the surface metal component and basic functional groups on the FMSAC were the main catalytic reaction sites.The result of electron paramagnetic resonance(EPR)analysis of FMSAC and FMSAC adsorption test of p-nitrophenol(PNP)showed that there was persistent organic macromolecule radicals(EPFRs)formed on the surface of FMSAC,which may enhance the removal of organic matter during FMSAC catalytic ozonation process.Transition metals(Mn,Co and Cu)doped ferromagnetic sludge-based activated carbons(T-FMSAC)were prepared by chemical co-precipitation method.The result showed that when the dosages of ozone and catalyst were 1 mg/L and 40 mg/L,respectively,the 100:1 Mn-FMSAC exhibited highest catalytic activity after 40 min.The removal rate of p-CBA during 100:1 Mn-FMSAC catalytic ozonation was 76%.The catalytic ozonation process followed the hydroxyl radical reaction mechanism.