Catalytic Degradation Of Plasticizer Endocrine Disruption Chemicals(EDCs) By Biochar-layered Double Hydroxide Composites

In the past few decades,the presence of plasticizer endocrine disruption chemicals（EDCs）（such as bisphenol A（BPA）and phthalates（PAEs））in drinking water,surface water and wastewater has increased significantly,which can affect the normal operation of natural hormones and greatly threaten the health and safety of human and other organisms,so the efficient removal of plasticizer EDCs in the aquatic environment has become a problem of environmental pollution control.Advanced oxidation processes（AOPs）based on photocatalytic and peroxymonosulfate（PMS）activation have attracted wide attention and research in the field of environmental remediation due to their good ability to degrade organic pollutants.However,the preparation of efficient,environmentally friendly,and low-cost advanced oxidation catalysts to achieve the efficient degradation of plasticizer EDCs remains a challenge.In this study,in order to achieve the purpose of rapid removal of plasticizer EDCs pollutants in polluted water bodies,a series of BC@LDH advanced oxidation catalysts with different types and functions were prepared using biochar（BC）and layered double hydroxide（LDH）as precursors,which were used to construct photocatalytic and PMS advanced oxidation systems,respectively.The microstructural characteristics of as-prepared advanced oxidation catalysts,the reaction mechanism,and the degradation dynamics of different EDCs were explored by using modern spectroscopy.The mechanism of the synergistic effect between BC and LDH on enhancing the degradation effect was clarify deeply.Furthermore,the degradation pathway and mechanism of EDCs in different advanced oxidation systems were explored through experiments and density functional theory（DFT）calculations.The main contents and results of this study are as follows:（1）Hydrochar@FeAl-LDH（hydrochar-LDH）composite photocatalyst was prepared by simple hydrothermal synthesis for the treatment of contaminated wastewater containing diethyl phthalate（DEP）.The interaction mechanism between FeAl-LDH and different compositions of hydrochar（hydrothermal carbon matrix（HCM）and dissolved organic matter（DOM））was further explored,and the influence on the generation of reactive oxygen species（ROS）in the photocatalytic system was analyzed.We found that after functionalized modification with FeAl-LDH,the photocatalytic activity of hydrochar was improved,and the content of oxygen functional groups（OFGs）,defects,and oxygen vacancies in hydrochar-LDH was significantly higher than those in hydrochar.Both HCM-LDH and DOM-LDH could produce ROS,including·OH,O₂·^-,and ¹O₂,where HCM-LDH played a major role in photodegradation by producing O₂·^-and·OH.And HCM-LDH had many oxygen-containing functional groups,which were key factors affecting ROS formation.There were some synergistic effects between FeAl-LDH and hydrochar.On the one hand,hydrochar promoted the crystallization of FeAl-LDH from micrometer level to nano-scale three dimensiona layer,thus improving the catalytic activity of FeAl-LDH.On the other hand,the layer structure Fe（II）of FeAl-LDH could promote the electron transfer in the photocatalytic process,thus promoting the photogeneration of O₂·^-,H₂O₂,·OH in hydrochar.As a result,the degradation efficiency of DEP(20 mg L^-1)by hydrochar-LDH was four times higher than that by unmodified hydrochar under a 500 W xenon lamp within 180 min,greatly enhancing the photocatalytic potential of hydrochar-based materials.（2）The catalytic performance of the FeAl-LDH/PMS system was enhanced by simply combining DOM.We further prepared DOM@FeAl-LDH（DOM-LDH）composite catalyst,and explored the excellent physicochemical properties and PMS catalytic properties.The results of characterization experiments demonstrated that the physicochemical properties of DOM-LDH were significantly better than FeAl-LDH,including:（a）The addition of DOM improved the structural properties of the catalyst,DOM-LDH had a larger specific surface area,pore size,and pore volume,which facilitated the interaction among catalyst,PMS,and BPA;（b）Humic acid compounds of DOM enriched the functional groups and oxygen vacancies on LDH’s surface;（c）The compounding of DOM significantly increased the trans-coordinated octahedral Fe（II）in FeAl-LDH,which prolonged the process of PMS activation.In addition,DOM could mediate the electron transfer,thus accelerating the reduction of Fe（III）to Fe（II）in FeAl-LDH,which could promote the PMS activation process.Compared with FeAl-LDH/PMS system,more ROS were produced in DOM-LDH/PMS system,including O₂·^-,SO₄·^-,¹O₂,and·OH,in which·OH was identified as the most important ROS in the BPA degradation.As a result,DOM-LDH/PMS system showed superior degradation performance,with 93%degradation efficiency for BPA(20 mg L^-1)within 60min,while only 60%degradation efficiency was achieved in FeAl-LDH/PMS system.（3）With pyrolysis carbon as the precursor,the BC@Co Fe-LDH（BC-LDH）composite catalyst was prepared by hydrothermal synthesis to clarify the mechanism of the efficient degradation of dimethyl phthalate（DMP）by activating PMS.The composition structure and catalytic properties of BC-LDH composite were explored and the characterization results were shown:（a）As a good carrier,BC showed rough and porous surface,which prevented the agglomeration and loss of Co Fe-LDH,and increased the specific surface area and pore volume of material;（b）More surface oxygen vacancies,defects and functional groups appeared in the surface of BC-LDH,which could promote the electron transfer between catalyst and PMS with stronger electron transfer ability;（c）Those phenolic hydroxyl groups in BC could act as electronic donors to promote the reduction of Co（III）/Fe（III）into Co（II）/Fe（II）,respectively,thereby improving the activation performance to PMS;（d）O₂·^-,SO₄·^-,·OH,and ¹O₂were presented in BC-LDH/PMS system and significantly higher than those in Co Fe-LDH/PMS system,among which·OH and SO₄·^-played major roles in DMP degradation.Thanks to the synergistic effect between BC and Co Fe-LDH,BC-LDH composite showed excellent catalytic activity,and the DMP(10 mg L^-1)degradation rate reached 100%within 60 min,while in Co Fe-LDH/PMS system,DMP degradation rate was only 62%.Moreover,BC-LDH/PMS system also showed good DMP degradation effect when applied to actual water.In conclusion,we prepared a series of BC@LDH composite advanced oxidation catalysts for achieving rapid degradation of BPA,DMP,and DEP pollution.Both BC and LDH are environmental functional materials with low price,simple synthesis,and green environmental protection.It is of important theoretical value and research significance to explore their application potential in advanced oxidation and catalytic degradation of plasticizer EDCs.This work is expected to provide new insights on the application of BC and LDH for environmental remediation.