Activation Of Persulfate By Magnetic Biochar For Organic Contaminants Degradation In Water

With the rapid development of industrialization and civilization,the worldwide environmental crisis has prompted the rapid development of green advanced processing technology in order to create a healthy living environment and a sustainable future.The effective control and elimination of harmful pollutants in polluted water systems and recycling of domestic and industrial wastewater have been major strategies.Due to the high toxicity,low biodegradability and persistence of emerging organic pollutants(such as EDCs,PPCPs,etc.),traditional physical methods(such as adsorption,flocculation,etc.)and biodegradation methods can not effectively remove these organic pollutants.Thus,many advanced treatment technologies have been developed in recent years.Advanced Oxidation Processes(AOPs)have become the most effective way to treat these pollutants,which aim to decompose organic pollutants in water system into carbon dioxide and water completely,or act as a preliminary treatment process for transforming high resistance and toxic compounds into small molecular compounds with less harmful effects.Among them,the persulfate-based advanced oxidation process by activing peroxydisulfate(PS)or peroxymonosulfate(PMS)to produce sulfate radicals is widely used in envirornmental remediation,due to its advantages of high efficiency,thoroughness,environment friendly and mild reaction conditions.Biochar has attracted increasing attention as a heterogeneous catalyst for persulfate activation due to its low cost,high specific surface area,abundant oxygen-containing functional groups,adjustable electrical conductivity and physicochemical properties.In order to solve the problems of low activity and difficult separation of pure biochar,magnetic transition metal nanoparticles were combined with biochar in this paper.Banana peel is used as biomass,magnetic metal oxides are dispersed into biochar matrix to prepare magnetic biochar by a noval"one-pot",method.Then the magnetic biochar used as persulfate activator to degrade organic pollutants in water.The catalytic activity of persulfate by magnetic biochar and the reaction mechanism of contaminants degradation were investigated.The contents are summarized as follows:1 The magnetic biochar(?-Fe2O3@BC)derived from banana peels was synthesized by a facile one-pot thermal process and used as the cost-effective and recyclable PS activator for organic contaminants degradation.The results showed that the encapsulated iron oxide nanoparticles not only introduced the magnetism into biochar for easy separation,but also influenced the catalytic ability for PS activation.The y-Fe203@BC was found to be highly effective for bisphenol A(BPA)degradation without pH adjustment.A complete removal of BPAwhich was obtained within 20 min with an observed rate constant(kobs)of 0.1849 min-1,was almost two times as large as that(0.0956 min-1)of pure biochar.Further,it exhibited high mineralization efficiency for the degradation of various organic contaminants.Radical quenching experiments and electron spin resonance(ESR)studies confirmed that OH·,SO4·-and O2·-were all involved in the radical oxidation process which was responsible for BPA degradation.A mechanism of PS activation by the?-Fe2O3@BC catalyst was proposed based on the synergistic effect of biochar and iron.The degradation pathway of BPA was also investigated.2.Magnetic biochar(Co-BC)was synthesized by a facile one-pot method and used as a PMS activator to degrade 4-chlorophenol(4-CP).Co-BC has a high catalytic activity for PMS.In the presence of 2 mM PMS5 0.2 g/L CO-BC can remove 50 mg/L 4-CP completely within 20 min.Furthermore,the kobs(0.3184 min-1)in this reaction process was much larger than that in BC/PMS syatem(0.0082 min-1)and CoO/PMS system(0.0213 min-1).In this chapter,the effects of catalyst dosage,PMS concentration,initial pH value and reaction temperature on the degradation of 4-CP in Co-BC/PMS system were investigated in detail.Radical quenching experiments and electron spin resonance(ESR)studies showed that existence of OH-· SO4·-?O2·-and 1O2·The possible mechanism of persulfate activation by y-Fe2O3@BC for BPA degradation was proposed based on both free radical and non-free radical reaction process.