Performance And Mechanism Of Organic Pollutants From Water By Activated Persulfate With Sludge Biochar

With the development of industrial level,various refractory pollutants（such as dyes,antibiotics,etc.）are discharged into water,and water pollution treatment has become an important topic in the field of environment in recent years.Advanced oxidation technology based on peroxydisulfate（PDS）has attracted more attention due to its strong oxidation capacity and low cost.Among many activation methods,biochar materials are widely used for the activation of persulfate due to their advantages of wide sources,low cost and adjustable structure.In this paper,paper sludge biochar was used to activate PDS to degrade organic pollutants in water,its adsorption and catalytic properties were explored,and the catalytic mechanism was systematically described.The main research results were as follows:（1）The iron-containing sludge biochar（Fe-SDBC）was prepared in situ by one-step pyrolysis from the flocculating paper sludge,and was used to activate PDS to degrade acid orange 7（AO7）.The characterization results of biochar showed that Fe-SDBC had rich oxygen-containing functional groups and good pore structure,and rich in iron species.Under the optimum conditions,the degradation rate of AO7 could reach98.4%in 5 minutes.The effects of different factors（Fe-SDBC dosage,PDS concentration,p H and anions）on the degradation system were studied,and the reaction conditions were optimized accordingly.Different from the traditional PDS activation process,there were both free and non-free radical pathways in the system of Fe-SDBC/PDS.The free radical pathway included various active oxygen such as SO₄^·-,·OH and O₂^·-.The non-free radical pathway was dominated by ¹O₂ and electron transfer.In addition,Fe-SDBC showed excellent reusability.This study provided a new insight for the application of flocculating sludge biochar in activated PDS.（2）Taking mineral-rich Fe-SDBC as the research object,water soluble minerals and endogenous minerals in biochar were removed by washing and acid washing respectively,and endogenous mineral retaining biochar（Fe-WSDBC）and graphite carbon retaining biochar（Fe-ASDBC）were obtained.Three kinds of biochar were used as activators of PDS to remove tetracycline（TC）.The results showed that Fe-SDBC had the best adsorption capacity for TC,while Fe-ASDBC had the best PDS catalytic capacity,The system of Fe-WSDBC/PDS might promote the adsorption of TC and the formation of·OH,and hinder the electronic transfer of the system.The system of Fe-WSDBC/PDS could promote the formation of system ¹O₂.This study revealed the effect of mineral components in sludge biochar on the degradation of TC,which has an important contribution to further understand the environmental significance of biochar.（3）The flocculation biochar was further modified by ball milling（Fe-MSDBC）,and showed high removal capacity in high concentration TC solution.When the initial TC concentration was 200 mg/L,the Fe-MSDBC/PDS system could degrade 86.06%of TC in 90 min.The characterization results confirmed that the proportion of oxygen-containing functional groups on the surface of the biochar increased after ball milling,the Fe-MSDBC also had smaller particle size and better hydrophilicity.The free radical quenching experiment and electrochemical test showed that·OH、SO₄^·-and O₂^·-were the main active oxygen species in the reaction system.At the same time,the electron transfer between in the Fe-MSDBC/PDS/TC system was also the main contribution for TC degradation.The degradation path of TC was further clarified by LC-MS combined with theoretical calculation.Finally,the application of the Fe-MSDBC/PDS system in the actual paper wastewater was evaluated.This research provided a new insight into the mechanism of pollutant degradation of ball-milled biochar.and a theoretical basis and technology for the use of ball-milled biochar in actual wastewater.