Activation Of Persulfates By N-Doped Graphitic Biochars:Oxidation Of Tetracycline By Nonradical Mechanism

As notorious pollutants,pharmaceuticals and personal care products?PPCPs?are widely distributed and have irreversible negative impacts on human beings and ecosystems.The issues have prompted scientists to develop green and sustainable technologies to eliminate global environmental pollution.Through radical and nonradical mechanisms,advanced oxidation processes?AOPs?are effective for prompt removal and even mineralization organic pollutants.In contrast to nonselective radical mechanisms,nonradical mechanisms shows a high reactivity toward electron-rich moieties and thus are less susceptible to hindrance by background constituents,halogen and other anions in water.Therefore,it is more suitable for salt water and certain pollutants.In this study,we reported N-doped graphitic biochars?N-BCs?with different N contents as low-cost and efficient catalysts for peroxydisulfate?PDS?activation and the degradation of tetracycline.N-doped graphitic biochars with highly graphitic nanosheets and rich doped nitrogen were successfully synthesized via direct pyrolysis of a mixture of camphortree leaf powder and dicyandiamide.The morphologies,chemical states and performance for the tetracycline degradation were characterized and explored.Raman spectrum shows that the defect degree was improved by doping N.XPS results reveal that the main nitrogen species is pyridine N.N-doped graphitic biochars exhibited excellent degradation rate,which was 2.31-fold of that on pristine biochar,despite the fact that the specific surface area of N-doped graphitic biochar decreased 64.1%.The evolution of radical species was monitored with electron paramagnetic resonance?EPR?technique.¹O₂ played a major role on the degradation process rather than SO₄^·-and·OH.This study proposes new insights into the mechanism of PS activation by biochar and an efficient method for PPCP removal.