Manganese Ion Release Characteristics And Load Filtration Performance During The Degradation Of Antibiotics By Manganese Dioxide

With the development of China’s economy and the improvement of people’s living standards,people pay more and more attention to the living environment.In recent years,with the continuous improvement of detection technology,the detection rate and types of organic micro-pollutants in water environment have been increasing year by year,and the detection of organic micro-pollutants in water has aroused people’s concern about water safety.In order to solve the problem of water shortage,China has vigorously promoted the wastewater recycling technology,but the secondary effluent of sewage treatment plants antibiotic drugs residual pollution is serious.The direct recycling of wastewater from off-plant drainage has unforeseeable potential harmful effects on human health and ecological environment.Therefore,it is urgent to develop an efficient,green and economic advanced treatment technology for reclaimed water.Studies have shown that manganese dioxide can adsorb and degrade antibiotics without producing disinfection by-products,so it is a kind of solid phase material with high efficiency and low consumption.In this study,artificially prepared organic wastewater containing antibiotics and two kinds of common manganese dioxide were used to simulate the adsorption and degradation of antibiotics in wastewater by manganese dioxide.The release of manganese ions and the removal rate of antibiotics,the operation of the filter column loaded with manganese dioxide,the antibiotic resistance genes and the community composition of microorganisms in the filter column were studied.It is expected to provide reference for the control of antibiotic pollution by wastewater recycling in practical engineering.Manganese ion is a by-product of manganese dioxide（Mn O₂）degradation of antibiotics,resulting in loss of Mn O₂ activity and secondary contamination,which is not desirable for its use.Therefore,ciprofloxacin（CIP）was used as electron donor to study the release behavior of manganese from manganese dioxide,and to find an effective way to regenerate manganese dioxide.The results show that the release amount of manganese under acidic conditions is negatively correlated with p H value,and linearly positively correlated with the amount of manganese dioxide and CIP concentration.Dissolved oxygen has no significant effect on the release of manganese ions,but the existence of coexisting ions promotes the release of manganese ions.The analysis of BET,SEM,XRD and XPS shows that the self-made manganese dioxide can improve the surface area,change the surface morphology,reduce the crystallinity and maintain the distribution of manganese valence state,which is beneficial to the degradation of antibiotics.The operation of the filter column loaded with manganese dioxide shows that controlling the release of manganese is very important for the regeneration of manganese dioxide.The chemical oxidants（KMn O₄,H₂O₂）can restore the activity of Mn O₂ but are not conducive to the control of the release of Mn ions.The bacteria inoculated in the filter column can continuously control the release of manganese in situ,which is a convenient and economical method.The removal rate of 70%can still be maintained after repeated operation.The higher filtration rate is not conducive to the removal of CIP and the control of Mn release,and the long-term high load operation is not conducive to the recovery of Mn oxide activity and the control of Mn ion release.No resistance genes were detected in the filter columns,and the growth rates of the manganese oxidizing bacteria indicated that antibiotic concentrations of50 and 100 ng/L promoted their activity,but were inhibited at 500 and 1000 ng/L.An antibiotic level of 100 ng/L appears to be the critical concentration to inhibit or promote the growth rate of manganese oxidizing bacteria.The microorganism community structure on the sand samples before inoculation was different from that in the filter column.The microorganisms were acclimated and induced during the operation of the filter column.The increased proportion of Alpha-Proteobacteria in the filter column indicated that the filter column had enrichment effect on the manganese oxidizing bacteria,and the successful cultivation of the genus Leptothrix in the manganese oxidizing bacteria made the filter column capable of regenerating manganese.