Study On Degradation Of Carbamazepine By Electro-activated Persulfate With Fe-based Particle Electrode

In recent years,pharmaceuticals and personal care products（PPCPs）have been detected frequently in water environments.Among them,carbamazepine is one of the most used drugs.Because of its strong persistence and biodegradability,carbamazepine is almost difficult to remove in conventional wastewater treatment process.Sulfate radical-based advanced oxidation process（SR-AOPs）has been received increasing attention in the field of water treatment.Among them,the electro-activation of persulfate（PS）has attracted much attention due to its environmental friendliness,high efficiency,and convenient operation.However,it still has some problems such as small effective electrode area,high power consumption and low mass transfer efficiency.To overcome the above problems,Fe-Cu sulfide/granular activated carbon particle electrode（FCSG PE）and Fe-molybdenum disulfide/granular activated carbon particle electrode（FMSG PE）were introduced into the PS electro-activation in this research,and three-dimensional（3D）electro-activation of PS was constructed.The degradation of carbamazepine by PS electro-activated with Fe-based particle electrode was studied.The main contents and conclusions in this research are as follows:（1）FCSG PE and FMSG PE were successfully prepared by hydrothermal method.According to scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）and X-ray diffraction（XRD）,the elements of Fe,Cu and S were confirmed to exist on the surface of FCSG PE,and they mainly existed as CuFeS₂.The surface of the FMSG PE was composed of the flower-like structure and the addition of Fe did not change the crystal structure of molybdenum disulfide,indicating that the synthesized FMSG PE had high purity.（2）The experimental results of the degradation of carbamazepine by PS electro-activation with FCSG PE（E-PDS-FCSG）showed that the introduction of FCSG PE significantly improved the degradation of carbamazepine.Under the conditions of PDS concentration of 2.0 m M,FCSG PE dosage of 0.3 g/L,current density of 3.0 mA/cm²and initial pH value of 5,the removal rate of carbamazepine in the E-PDS-FCSG system reached 98.0%in 25 min,which was more than 2 times that of the two-dimensional PDS electro-activation（E-PDS with 48.2%removal rate）and 1.74 times that of the three-dimensional system with GAC as particle electrode（E-PDS-GAC）.Sulfate radicals(SO₄^·-)and hydroxyl radicals（·OH）were identified as the main active free radicals by radical quenching experiments,electron paramagnetic resonance（EPR）and Fe（IV）-PMSO probe experiment.PDS was activated jointly by the electron transfer of the cathode and the low-state metal ions on the surface of the FCSG PE.The low-state metal ions could not only be regenerated through the electron transfer between the bimetals,but also be regenerated under the electric field.In addition,the FCSG PE as microelectrode could directly activate PDS and enhance electron transfer.Thus,it promoted the Fe²⁺/Fe³⁺and Cu⁺/Cu²⁺cycle.What’s more,the reaction kinetic constant of E-PDS-FCSG was 6.11 times that of E-PDS,and the energy consumption of E-PDS-FCSG was only one third that of the E-PDS system,which further proved that the E-PDS-FCSG system had excellent oxidation capacity and good synergy between E-PDS and FCSG（synergism index was 5.05）.（3）The carbamazepine degradation was further improved by replacing FCSG PE with FMSG PE.The removal rate of carbamazepine in the E-PDS-FMSG system could reach more than 99%within 20 min.Mo S₂,as a co-catalyst,could not only activate PDS to produce SO₄^·-,but also further promote the Fe²⁺/Fe³⁺cycle.Compared with PDS electro-activation（E-PDS）,E-PDS-FMSG showed better catalytic ability and lower energy consumption.The reaction kinetic constant of E-PDS-FMSG was 8.14 times that of E-PDS on carbamazepine removal.Under the same conditions,the energy consumption of E-PDS-FMSG was about 36.3%that of E-PDS.In addition,E-PDS and FMSG showed excellent synergistic effect with synergism index of 7.20.Radical quenching experiments,EPR and Fe（IV）-PMSO probe experiment showed that in addition to SO₄^·-and·OH,Fe（IV）also existed in the E-PDS-FMSG system,and the combination of various active substances increased the removal rate of carbamazepine.It was found that the degradation of carbamazepine was promoted by increasing the concentration of PDS and the dosage of FMSG PE.But it was not conducive to the reaction under the excessive current density.In addition,initial p H value had little effect on carbamazepine degradation and the E-PDS-FMSG system had high degradation ability on carbamazepine removal in the initial p H value range of 3-9.Compared with the E-PDS-FCSG system,the E-PDS-FMSG system with high stability was less affected by reaction conditions.The presence of Cl^-in solution had a significant promoting effect on carbamazepine removal,while H₂PO₄^-and humic acid（HA）could inhibit the degradation of carbamazepine.And NO₃^-had little effect on carbamazepine degradation.FCSG PE and FMSG PE have the advantages of simple preparation,low cost,and excellent catalytic performance.E-PDS-FCSG and E-PDS-FMSG could not only improve the removal rate of carbamazepine,but also reduce the energy consumption,making up for the shortcomings of the traditional PDS electro-activation and expanding the application of SR-AOPs.