| As the modern industry developed rapidly,a variety of highly toxic aromatic pollutants released into the environment has caused serious water pollution problems.Therefore,the development of efficient aromatic pollutants removal technology is of great significance to human beings health and ecological environment.Nanozymes are highly efficient catalysts with both biocatalysis and chemical catalytic properties,but there are two limitations of catalytic activity and substrate selectivity.Thus,it is significant to design biomimetic catalysts with precise catalytic sites and high performance for the removal of aromatic pollutants.Based on the density functional theory(DFT)calculations,biodegradation mechanisms of aromatic organic compounds and chemical conversion mechanisms of persulfate activation to remove pollutants were comprehensively analyzed.The enzyme-like single atom catalyst for aromatic arsenic oxidation and transformation was designed and synthesized,and further works were devoted to extend the the capability in practical application.This thesis provide a new way and platform for designing the catalysts to remove aromatic organic pollutants.The main content and results of this thesis are as follows:1.The reductive transformation mechanism of organic arsenic via electrochemically active bacteria.In order to study the biotransformation process of nitarsone by Shewanella oneidensis MR-1,the interaction between nitarsone and the active center of the key outer membrane protein OmcA was analyzed and three possible nitarsone transformation pathways were evaluated by DFT.The results implied that nitarsone accepted bioelectrons by interacting with the protein OmcA,and the interaction strength was increased by the intermolecular force of the electrostatic interaction,the conjugation effect,and hydrogen bonding.Moreover,the reduction of nitro group is the first step during the nitarsone reduction process,and then the cleavage of carbon-arsenite(C-As)bond for the generation of the inorganic arsenic and aniline.Thus,the theoretical basis could be provided for the design of biological treatment methods based on the extracellular transformation of organic arsenic and also the design of enzyme-like catalysts.2.Activation mechanism of persulfate by single-atom catalysts for organic pollutants conversion.The active centre of the single-atom catalysts is similar to that of enzyme.To give insight into biomimetic catalytic process of the single atom catalysts,the mechanism of persulfate activation by single atom catalysts(Cu SSCs and Mn SSCs)was analyzed by DFT calculations.The persulfate and dissolved oxygen are the main source species of 1O2,and the activation mechanisms of oxidation of persulfate and reduction of oxygen through charge transfer of two typical single atom catalysts was illustrated.This work provides the design idea for the development of enzyme-like single-atom catalysts for target aromatic pollutants.3.Single Mo atom catalyst inspired by the arsenic redox enzyme for organic arsenic transformation.In order to efficiently achieve the conversion of organic arsenic(para-arsanilic acid,ASA)in water,inspired by the active center structure of the arsenic redoxtase,a single atom catalyst with the coordination structure of MoS4(Mo SAs/SG)was designed and synthesized.The perdisulfate(PDS)was introduced as oxidant.And DFT calculation was performed to analyze the specific reaction process.The theoretical and experimental results show a high ability of ASA transformation on Mo SAs/SG Under the optimized condition,the pseudo-first-order kinetic constant was 0.055 min-1,the conversion ratio of ASA was over 90%.The electrochemical test,active species capturing experiments and theoretical calculations reveal a direct electron transfer process exists between the Mo SAs/SG,the PDS and the ASA molecules.This wok provides the feasible solutions for the design of single atom catalysts to achieve the enzyme-like functions for environmental applications.4.Electrocatalytic conversion of organic pollutants by S and oxygen vacancies(Vos)co-existing molybdenum oxide(S-MoO3-x).To broaden the substrate range of enzyme-like catalyst and also expand the practical application capabilities of the series of catalysts containing Mo,S-MoO3-x was obtained for electrochemical reduction of CAP.The experimental results showed that S-MoO3-x material had a good electrocatalytic ability of CAP reduction,and performed better under the optimized conditions,where the rate constant of the first order reaction was 0.023 min-1,and reduction ratio of CAP was over 98%within 3 hours.To discuss the reduction mechanism,electrochemical tests and DFT calculations were performed.The reduction process was a catalytic reduction dominated by adsorbed-hydrogen(*H),achieved by the co-existence of S and VOS.This work provides the efficient way for the enhancement of enzyme-mimc catalysts for environmental remediation. |
PDF Full Text Request