Preparation Of Biochar Derived From Tangerine Wastes And Its Application For Peroxymonosulfate Activation

With the development of industry,the problem of pollution becomes more and more serious.Antibiotics,dyes,phenols and other organic pollutants in water pose a great threat to human health and ecological balance.The advanced oxidation technology based on persulfate has attracted increasingly attention in recent years.Persulfate can be activated in many ways,and sulfate radical,hydroxyl radical or singlet oxygen and other active substances are generated.These substances can rapidly mineralize organic pollutants in water.In order to improve the efficiency of activated persulfate,reduce the secondary pollution and the cost of treatment.Environment friendly and low-cost biochar is the best choice as persulfate activator.Currently,the amount of reports about the persulfate activation by modified biochar is increasing,but the relationship between the composition of biomass and the catalytic performance of biochar is still unclear.In addition,the main active sites on the biochar for activating persulfate need further study.This paper will take tangerine waste as an example and discuss it in the following:（1）Tangerine pith derived biochar（TP-900）and tangerine peel derived biochar（e-TPs-900）were prepared by one-step pyrolysis.Material characterizations analysis showed that TP is mainly composed of cellulose,and there are many mesoporous in TP-900which specific surface area reached 922.13 m²g^-1.While,the main component of e-TPs is lignin,and the proportion of micropores of e-TPs-900 is 72.0%.It was observed by electron microscope that the cellulose in TP was fragmentary after pyrolysis at high temperature,while the structure of e-TPs-900 was still massive.In contrast to e-TPs-900,TP-900exhibited excellent PMS activation ability.What is more,it is confirmed that C=O on the biochar surface is the main active site to activate PMS to produce singlet oxygen which dominated the oxidation process.By adjusting the proportion of lignin and cellulose to simulate different biomass,it was found that increasing the proportion of cellulose could improve the catalytic performance of biochar.In addition,temperature is also one of the factors that affect the structure and performance of the material.The graphitization degree of biochar is higher at higher temperature,and its catalytic performance is better.（2）P-Mn-TPs-900 and Mn-TPs-900 were prepared by one-step pyrolysis.The characterization results showed that the specific surface area and porosity of biochar can be improved by pickling biomass with dilute phosphoric acid.The catalytic ability of biochar can be improved by loading manganese oxides.The electron microscopy results showed that P-Mn-TPs-900 is a small fragment with rough surface,and the metal is evenly distributed on the surface of the material.In contrast,the surface of Mn-TPs-900 is smooth and massive,and the metal agglomeration is obvious.Raman results showed that the graphitization degree of P-Mn-TPs-900 is higher compared with Mn-TPs-900.Compared with Mn-TPs-900,P-Mn-TPs-900 has better cyclicity and can rapidly activate PMS in the p H range of 4～10.the experiment results indicated that singlet oxygen dominated the oxidation process in the P-Mn-TPs-900/PMS system.XPS analysis and theoretical calculation revealed the role of C-O-Mn on the biochar surface.