Construction Of Photoelectro-Fenton Processes Based On Novel Catalytic Cathodes And Their Degradation Of PhACs In Water

Novel organic pollution characterized by pharmaceutically active compounds(PhACs)has become one of the major water environment issues with global concern.These pollutants often cannot be degraded efficiently by traditional biochemical processes and they finally ended up in the environment.PhACs have been frequently detected in rivers,lakes,oceans,and even drinking water,which may cause a series of environmental problems and threaten human health.Electrochemical advanced oxidation processes(EAOPs)can produce strong oxidants hydroxyl radicals(^·OH)through synergistic effect of electric field by using electron as reactant,which is able to oxidize refractory organic pollutants efficiently.EAOPs are considered as efficient,environmentally friendly,and clean technologies.In EAOPs,the photoelectro-Fenton(PEF)process can improve the oxidation ability by introduce UV light to enhance electron transfer,which can completely mineralize pollutants and has good application prospect.The performance of PEF process is mainly affected by the cathode surface electron transfer velocity and mass transfer efficiency on cathode surface.In this study,the PEF system with high catalytic activity to 2e^-oxygen reduction reaction(2e^--ORR)were constructed by preparing and optimizing novel biomass materials.The relationship between the surface properties,structure-function relationship,and catalytic mechanisms of cathode materials were discussed.The oxidation efficiency and degradation mechanisms of PhACs in treated water were studied.Finally,a self-sustained environmentally friendly wastewater treatment unit based on the coupling of solar photovoltaic cell and solar PEF was constructed on this basis and the feasibility of PEF practical applications was also examined.The main research content and conclusions were summarized as follows:(1)Research on the development of non-metal doped biochar-catalyzed cathodes and their oxidation pollutant laws:A novel chitosan biochar was prepared and non-metal doped with 1,10-phenanthroline.The microscopic morphologies,surface groups,and electrochemical catalytic activities were estimated.It has been proved that nitrogen-modification process improves the pore structure and specific surface area of catalyst(improved from 6 to 63 m² g^-1),increase surface nitrogen content and graphitization degree,which can enhance electron transfer and 2e^--ORR selectivity.A gas diffusion electrodes(GDE)preparation process was successfully developed to prepare a GDE cathode with core of biochar.The 2e^--ORR performance and oxidation ability of treating acebutolol(ACE)of different catalysis cathode were studied.The results indicated that N-doped biomass GDE exhibited much better ability for H2O2generation and can degrade acebutolol(ACE)in water efficiently.By paired to a nonactive BDD anode,complete mineralization could be achieved after 360 min PEF treatment of 0.046 m M ACE using N-doped GDE.Six aromatic and 5 aliphatic degradation products were detected.The initial N in ACE molecule was preferentially converted into ammonium and released.(2)Enhanced 2e^--ORR performance by adjusting the microstructure of biochar and its efficiency in PEF process:In order to further improve the preparation method and enhance catalytic efficiency,agarose underwent double-step pyrolysis and steam activation as carbon source to prepare catalysts with high specific surface area.By adjusting the activation time,the micromorphology of the catalysts could be improved and their specific surface area and the Vm/V?ratio were increased.After 20min treatment,the specific surface area of carbon material was the highest(1248 m²g^-1).Prepared GDE yielded excellent 2e^--ORR activity.After 30 min treatment,the current efficiency was approximately 95%,which was higher than commercial electrode(75%).The effect of different water quality conditions on ACE oxidation efficiency and degradation mechanism were estimated.It was found that degradation rate under with same conductivity follows the law of actual wastewater<SO₄^2-/Cl^-<Cl^-<SO₄^2-.This indicates that the reactions between^·OH and Cl^-as well as H2O2 and active chlorine will result in a decrease in^·OH concentration and oxidation ability of the system.However,the presence of active chlorine in the system will oxidize ACE,yielding six chlorinated monobenzenes.The presence of NOM in actual wastewater also caused slower degradation and mineralization rate,the effective treatment could be realized by the adjustment of operation conditions.(3)Research on the PEF system regulation mechanism of ACF cathode based on highly efficient Fe(?)/Fe(?)cycle.ACF cathode surface properties were evaluated in terms of their catalytic mechanisms and efficiencies in PEF system.The results revealed that ACF cathode with higher specific surface area could provide more reaction sites,accelerating the DO catalytic reduction and Fe²⁺regeneration,and promoting^·OH production.The mineralization rate of ACF cathode with high specific surface area degrading 200 mg L^-1 cefalexin(CLX)could be over 76%.Generated inorganic ions,carboxylic acids,and aromatic products in the CLX degradation process were measured.ACF cathode with rich pore structure yielded more complete mineralization.PEF degrades CLX mainly by gradually oxidizing and damaging CLX molecular structure via sulfoxidation,hydroxylation,and decarboxylation.In the effluent,over 80%of TOCs existed as carboxylic acids and 71%of organic N was oxidized and released as inorganic ions.(4)Construction of self-sustained solar photovoltaic cell(SPC)-solar photoelectro-Fenton(SPEF)system and electro-optical synergy mechanism:The sunlight with continuous spectrum was used as energy and driving force,the SPC-SPEF core technique unit was matched via energy balance,and the environmental friendly wastewater treatment integrated device without external energy input was developed.The mineralization of 200 mg L^-1 trimethoprim(TMP)using this device could reach80%.The main operation conditions were optimized as 1.0 m M Fe²⁺,p H 3.0,and 18m A cm^-2via single factor experiment.Ten aromatic products generated from hydroxylation,carbonylation,and demethylation reactions were detected in TMP degradation process in SPEF system.This device could overcome the operation limit of sunlight hours in SPEF by mode shift(SPC-SPEF/PEF or SPC-SPEF/EF).This device provided a new idea for treating organic wastewater with high concentration in remote area.This self-sustained SPC-SPEF system has good reference value for practical application of PEF.