Study On Activation Mechanism And Active Sites Of Bagasse Biochar Activated Persulfate To Degrade Environmental Organic Pollutants

With the rapid development of industrialization,urbanization and population,a large amount of production and domestic wastewater is discharged into the environment at random,which has attracted more and more attention.Advanced oxidation technology as a solution to the treatment of organic pollutants in the environment has the advantages of good mineralization,strong oxidation capacity,relatively low cost and short treatment cycle.However,the traditional advanced oxidation technology has many disadvantages such as too narrow pH range,metal leaching,and limited application range.At the same time,the detailed mechanism of catalyst activation of persulfate still needs to be explored.The main research area of this paper is the use of biomass waste carbon materials to stimulate persulfate to generate active oxygen species to degrade common organic pollutants.The biochar catalyst used in this study is a new mesoporous carbon material(Ca/BS-800-KOH)prepared by using cheap and easily available bagasse as a carbon source,modified by CaCl2 and KOH,and further pyrolyzed.The performance of the material was evaluated by degrading some organic matter(phenol).We proposed the mechanism of modified bagasse with CaCl2 and KOH,and explored the structure and properties of the material using some characterization methods and experiment analysys.At the same time,the catalytic active site of the material was revealed,and the electron transfer process in the catalytic process was proposed.The details are as follows:1.In this paper,the bagasse biochar treated with CaCl2 and KOH(Ca/BS-800-KOH),unprocessed bagasse biochar(BS-800)obtained by calcining at 800℃ and other carbon materials(commercial biological materials and activated carbon)were used to activated persulfate(PDS)to degrade phenol.Ca/BS-800-KOH showed the best removal effect among many carbon materials.0.066 g/L of Ca/BS-800-KOH activated 1 g/L of PDS to completely degrade 20 mg/L of phenol in 90 min.Compared with BS-800,the specific surface area(1209 m2/g)and pore volume(1.231 cm3/g)of Ca/BS-800-KOH increased significantly.At the same time,according to FTIR spectroscopy,its oxygen-containing functional groups were also increased.This shows that CaCl2 and KOH treatment can improve the material’s adsorption and catalytic performance of pollutants via changing the chemical properties of the material surface.Compared with other carbon materials,Ca/BS-800-KOH shows the advantages of large specific surface area,relatively good reproducibility,lower dosage and cheap manufacturing cost.2.SEM and TEM results showed that the surface of Ca/BS-800-KOH treated with KOH and CaCl2 became relatively rough,and the thickness of the fragment structure was thinner.Combined with FTIR and specific surface area analyzer,it is found that the surface properties and structure of Ca/BS-800-KOH changed significantly compared to BS-800.Here,we proposed the mechanism for improving the adsorption and catalytic performance of biochar materials after treatment of bagasse with CaCl2 and KOH,namely physical activation,chemical activation,expansion and wrinkling of the carbon layer,and increased electrical conductivity.3.According to the results of X-ray photoelectron spectroscopy(XPS)and FTIR of Ca/BS-800-KOH before and after the reaction,it is found that phenol was adsorbed on the surface of Ca/BS-800-KOH and then was degraded.The content of-OH in the reaction is reduced from XPS analysis,indicating that it is converted into other oxygen-containing functional groups as the active site in the catalytic reaction.Raman spectroscopy shows that the ID/IG value after the reaction increases,indicating that the degree of graphitization of the material during the reaction is reduced,which is not conducive to electron transfer and PDS activation.4.The results of the quenching experiment show that both free radical and non-free radical pathways participated in the oxidative degradation of phenol,of which non-free radicals dominate.Electron spin resonance(ESR)results also confirmed that free radicals(SO4·-,·OH,O2·-)and singlet oxygen(102)exist in the reaction system.5.The degradation results of phenol in actual water samples and soil mud indicate that Ca/BS-800-KOH has the ability to degrade phenol in complex natural environments.Degradation curves of various pollutants suggest that Ca/BS-800-KOH has the ability to catalyze and degrade organic pollutants in a broad spectrum,and has good application potential.