Study On The Degradation Of Trichlorophenol By Light-induced Pyrochar From Sycamore Leaves Activated By Molecular Oxygen

As a common insecticide and disinfectant,polychlorinated phenols cause air,soil,and water pollution while facilitating daily life,and have been listed as a pri-control pollutant.Due to the abundant oxygen-containing functional groups（OFGs）and persistent free radicals（PFRs）,biochar can generate certain reactive oxygen species（ROS）under light induction.These ROS participate in and affect the transformation process of pollutants.However,at present,the research on the transformation mechanism of ROS is still insufficient,and the specific role of biochar in it is still unclear.Simultaneously,the impact of biochar on the photochemical transformation of pollutants in the environment also needs to be further studied.Based on the above problems,this paper took the pyrochar generated from sycamore leaves as the research object and explored the role of pyrochar in the process of ROS generation and transformation under light irradiation from the aspects of dissolved organic matter（DOM）,PFRs,and OFGs.The effects of iron modification on the structural properties and photochemical behavior of pyrochar and possible reasons were discussed by simulating the close combination of iron and pyrochar in nature.The detailed research contents are as follows:1.A series of pyrolytic carbon materials capable of generating ROS were synthesized by a simple one-step pyrolysis method.It was found that the SHC materials synthesized at300℃for 2 h had the relatively highest trichlorophenol（TCP）removal rate（48.80%）and H₂O₂produced an effect（14.62μmol/L）.By controlling the reaction atmosphere,light intensity,material synthesis conditions,and other variables,the relationship between the generation and transformation of ROS in this system was determined and perfected:¹O₂was mainly derived from O₂transformation,·O₂^-could be weakly generated in the dark,and H₂O₂production required the participation of light.By removing dissolved organic matter（DOM）,controlling the content of PFRs and OFGs,etc.,the production of ROS by biochar under light was investigated.It was proved that in the process of ROS production by SHC light,OFGs represented by-OH played an important role in transferring electrons and energy,mediated the production of·O₂^-and the formation of¹O₂and participated in the conversion of H₂O₂;PFRs played an important electron-donating role in the process of activating the conversion of H₂O₂to·OH.It was worth mentioning that PFRs could also participate in·O₂^-that was produced in small amounts and not affected by light;the role of DOM in ROS production was relatively weak.2.By comparing the interaction of several common iron ores and iron salts with SHC,it was found that SHC-Fe_0.2modified with iron nitrate as the iron source had a more stable structure and more obvious photochemical effects（The removal rate of TCP reached62.84%,which was 19.75%higher than that of SHC.）,which can be used as a model for the close combination of iron and pyrochar in the environment.Characterization experiments showed that iron was mainly complexed with oxygen atoms in the form of octahedral coordination on the pyrochar,which was an important reason for the stability of iron on the pyrochar.The experimental results of ROS detection and quenching indicated showed that iron modification promoted the generation of various ROS excepted ¹O₂by enhancing the electron-donating ability of pyrochar,and changed the pathway of pyrochar photoconversion to TCP from the non-radical type to free radical type,among which we found that the enhancement of the electron-donating ability of the pyrochar brought by iron modification was not affected by light.In addition,experiments on iron morphology and changes also showed that the slow release of free Fe²⁺brought about by the coordinated iron could mediate the Fenton process to accelerate the conversion of H₂O₂to·OH.