Synthesis Of High Efficient G-C₃N₄ Based Catalyst And Its Photocatalytic Degradation Mechanism Of Antibiotics In Water

The increasing water contamination by antibiotics is threatening the microorganism in water phase and the public health,which can induce antibiotic resistance genes(ARG)and the generation of antibiotic resistance bacteria(ARB).Aiming to remove antibiotics in water,this work studied the photocatalytic performance of g-C3N4-based catalysts on antibiotics removal under sunlight,which can provide foundation for the engineering application of photocatalytic methods to remove antibiotics in water phase.The main research contents and conclusions are as follows:By calcining the mixture of urea and 1,3,5-cyclohexanetriol,the g-C3N4 modified with carbon-rich functional groups on the surface was obtained,which was named C-CN90.The photocatalytic degradation of amoxicillin by C-CN90 is 2.3 times of pure g-C3N4.The material characterizations showed that the carbon-rich functional groups on the surface of C-CN90 was featured on the large π-conjugated structure of graphene.The difference in doping amount between the surface and internal carbon-rich functional groups of C-CN90 leads to the construction of built-in electric field(BIEF),which can drive the electrons from the inner to the surface layer.However,the light-induced holes still stayed in original layers,leading to the high separation efficiency of the electrons and holes.Moreover,the introduction of graphene’s largeπ-conjugated structure broadens the absorbance of visible light by C-CN90.Free radical quenching experiments showed that the contributions of various free radicals followed the order of·O2->h+>1O2.Based on the DFT calculation and intermediates analysis,the possible degradation pathway of AMX was proposed.The C-CN90 retained good stability after 5 reusing cycles;meanwhile,it showed good removal performance for pefloxacin,sulfathiazole and cephalexin,indicating that the C-CN90 had a wide applicability in removing antibiotics.The stability and applicability revealed that C-CN90 had high potential for engineering application.The environmental parameter studies showed that DOM had a greater impact on the photocatalytic system than pH,while SO42-has no significant impact,and there is no interaction between the three factors.Bi2WO6 and Cu were deposited on the surface of g-C3N4 by a facile hydrothermal method,and the modification of Bi2WO6 and Cu was explored.The photocatalytic degradation of SMZ by the optimal material(BC70+1%Cu)was explored under solar light.The SMZ removal efficiency is 3.4 times and 4.2 times than of pure g-C3N4 and pure Bi2WO6,respectively.The material characterizations showed that BC70+1%Cu could broaden the utilization of sunlight spectra,and improve the separation of photogenerated carriers,thus improving the SMZ degradation.The degradation path of SMZ was inferred based on intermediates analysis.Through free radical quenching experiments,the contribution of free radicals on SMZ degradation was found following the order of h+>·O2>1O2.The humic acids in water had limited effects on the degradation SMZ.80%of SMZ removal can be reached within 90 min,indicating that BC70+1%Cu is applicable to the different water quality.The reusing experiments indicated BC70+1%Cu had good stability.Therefore,the BC70+1%Cu had certain engineering application potential in actual water quality.The Bi24O31Br10 was deposited on g-C3N4 by a facile hydrothermal method to construct a g-C3N4/Bi24O31Br10 binary Ⅱ-type heterojunction(BCN3).The BCN3 exhibited excellent activity for ceftiofur sodium(CTFS)degradation,and activity of BCN3 is 1.3 and 4.0 times of pure g-C3N4 and Bi24O31Br10,respectively.The material characterizations showed that the enhancement of the activity of BCN3 was due to the construction of aⅡ-type heterostructure,which resulting in the efficient separation of photogenerated carriers in BCN3.Through free radical quenching experiments,the contribution of free radicals in the photocatalysis system was 1O2>O2->h+.Reusing experiments showed that BCN3 had good stability.A model of BCN3 photocatalytic degradation of CTFS was established through response surface methods.The p value of the model was 0.0351(<0.05)and the F value was 7.35,indicating that the model was highly significant.The significance of the pH,Dissolved Organic Matter(DOM)concentration and anion concentration(Cl-)on the photocatalytic system follows the order of pH>DOM>Cl-.According to the three-dimensional response surface and the corresponding two-dimensional contour map,there is no significant interaction between any two factors of pH,DOM and Cl-.