Study On The Adsorption Catalytic Behavior And Mechanism Of Iron-modified Biochar To Remove Refractory Organic Pollutants In Water

In recent years,there have been increasing environmental and toxicological interests about refractory pollutants such as antibiotic and phenolic compounds,due to their widespread occurrence,poor degradable nature and relative frequency in the aquatic environment.The traditional biological treatment method is not effective,so its treatment techniques has caused wide public concern.Biochar materials,with their large surface area and pore volume,have been proved to be very promising adsorbents,and their uniform mesopores are very suitable for the Fe supported.Moreover,the good adsorption performance of materials is favorable for the transfer and diffusion of the substrates,thus could enhance the catalytic efficiency of the Fe.In this work,a group of biochar-based adsorbents and catalyst were constructed.With their high effiency,easy operation and good reusability,these composites could be applied in the adsorption and degradation of some refractory organic pollutants.The adsorption and removal characteristics of the composites were discussed,and the removal mechanisms were revealed.Moreover,the effects of pH,temperature and time on the removal of the pollutants were also studied.And the optimum conditions for the application of those nZVI-based materials were achieved.More importantly,the potential for the application of these materials in wastewater treatment were also investigated.?1?The liquid phase reduction method can effectively load the nanometer zero-valent iron on the surface of the biochar,and partly into the pores of the biochar.The results of SEM and TEM confirmed that the particle size of the particles was between 30 and 70 nm,and the particles were dispersed uniformly.Most of the iron particles were spherical,and the load was parallel to the outer surface of the biochar.Characterization results showed that biochar was sheet like and with hydroxyl,carboxyl,carbonyl on the surface,which favor to the supporting of n-ZVI.?2?Highly efficient simultaneous removal of Cu?II?and tetracycline?TET?from aqueous solution was accomplished by iron and zinc doped sawdust biochar?Fe/Zn-biochar?.The mutual effects and inner mechanisms of their adsorption onto Fe/Zn-biochar were systematically investigated via sole and binary systems,sorption isotherm and adsorption kinetics models.The liquid-film diffusion step might be the rate-limiting step for tetracycline,the interaction of Cu?II?was more likely controlled by both intra particle diffusion model and liquid film diffusion model.The fitting of experimental data with kinetic models,Temkin model indicates that the adsorption process of tetracycline and Cu?II?involve chemisorption,and physico-chemical adsorption,respectively.There exists site competition and enhancement of Cu?II?and tetracycline on the sorption to Fe/Zn-biochar.The results of this study indicate that modification of biochar derived from sawdust shows great potential for simultaneous removal of Cu?II?and tetracycline from co-contaminated water.?3?Ecological risk of residual antibiotics has attracted increasing attention.In this study,a novel highly efficient catalyzer based on Fe nanoparticles modified biochar was prepared to remove antibiotics inaqueous solution.Effect of Fe loading,catalyzer dosage,initial solution pH and H₂O₂ dosage on the removal of antibiotics were investigated.In addition,the degradationproducts and possible degradation pathway of Levofloxacin,Ciprofloxacin and Pefloxacin by nZVI/BC/H₂O₂ systems were analyzed using High Performance Liquid Chromatography-Mass Spectrometry?HPLC-MS?.?4?In this work,to gain insight into the mechanism of p-nitrophenol?PNP?removal using the reactivity of biochar supported nanoscale zerovalent iron composite?nZVI/biochar?and nanoscale zero valent iron?nZVI?under anaerobic or aerobic conditions,batch experiments and models were conducted.The PNP removal rate in the more acidic solutions was higher,while it was significantly suppressed at higher pH,especially at pH 9.0.The peak value of the apparent rate constants suggests that the reactivity of nZVI/biochar could be much stronger than that of nZVI under the same aeration condition.The modified Langmuir-Hinshelwood kinetic model could successfully describe the PNP removal process using nZVI/biochar or nZVI.The reaction constants obtained through Langmuir-Hinshelwood under different aeration conditions followed the trend that nZVI/biochar?N₂?>nZVI/biochar?air?>nZVI?N2?>nZVI?air?,indicating that nZVI/biochar under anaerobic conditions exhibits enhanced activity for the degradation of PNP.The nZVI/biochar under anaerobic conditions has the lowest Arrhenius activation energy of PNP degradation-adsorption,suggesting that the surface interaction of eliminating PNP has low energy barrier.In addition,the TOC removal under the anaerobic conditions was negligible compared with that under the aerobic system and the total iron ions leaching at solution pH 3.0in nZVI/biochar or nZVI system under air aeration conditions were much higher than those under nitrogen aeration conditions.The profiles of the intermediates formed during the PNP degradation indicated that under the anaerobic environment,the reduction was the predominant step in the removal process,while the degradation of PNP could be regarded as a combination of oxidation and reduction under aerobic environment.