Study On Fenton-like Degradation Of Phenol-containing Wastewater By Magnetic Coal Gangue Geopolymer

In china,coal gangue stockpile has reached more than 7 billion tons,causing serious environmental pressure.But at present,the comprehensive utilization of coal gangue in China is still mainly concentrated in cement production,brick making and other low value-added fields,and it is urgent to explore the direction of high value-added utilization of coal gangue.As a new type of silica-alumina cementitious material,geopolymer（referred to as geopolymer）has received wide attention because of its excellent mechanical properties and high temperature resistance.In recent years,geopolymer also shows good acid resistance and adsorption performance in the research of wastewater treatment,and coal-associated solid waste has shown great potential in preparing into geopolymer as raw material,which becomes a feasible method to solve the solid waste problem.Meanwhile,there is little research on the preparation of geopolymer from coal gangue and its use in wastewater treatment.Phenolic compounds are widely used in industry and daily life,because of their stable structure and strong biotoxicity to cause serious harm to water bodies,how to efficiently and thoroughly remove the phenolic substances in water has become an urgent task.Traditional treatment technologies include physical,chemical and biological methods,among which Fenton-like oxidation is one of the most researched technologies due to its strong oxidation capacity and large treatment capacity,but the catalyst has the problems of instability and difficult to recover from suspension.Therefore,in this paper,magnetic gangue geopolymer（CGGP）was introduced in the preparation of coal gangue geopolymer（CGGP）as raw material,and magnetic gangue geopolymer was successfully prepared,and its performance of Fenton-like catalytic oxidative degradation of phenol-containing wastewater was investigated through single-factor experiments,and its application prospects were evaluated.The specific research of the paper is as follows.（1）CGGP was prepared by thermal activation and alkali excitation using CG as raw material.the adsorption performance of CGGP was investigated with phenol as the target pollutant,and the effects of gangue raw material type,thermal activation temperature,alkali excitation system,alkali excitation modulus,n（H₂O）/n（Na₂O）and n（Al₂O₃）/n（Na₂O）on the performance of CGGP were investigated.The experiments showed that the best raw material for the prepared materials was Datong coal mine gangue（DCG）,the best thermal activation temperature of the raw material was 800°C,the best alkali exciter system was Na OH and water glass,the best alkali exciter modulus was 1.2,the best n（H₂O）/n（Na₂O）=25,the best n（Al₂O₃）/n（Na₂O）=1.0,and the best preparation ratio was 60 min under the best preparation ratio The removal rate of 100 mg·L^-1 phenol could reach 13.49%.The characterization results showed that the"bulging peak"of the geomers appeared in the X-ray diffraction（XRD）spectra of CGGP between 17°and 32°at 2θ,and the FTIR spectra from 800 cm^-1 to 1200 cm^-1corresponded to the Si-O-T bond（T for Si or Al）asymmetric stretching vibration of the geomers.Al)asymmetric stretching vibration of the geopolymer,and scanning electron microscopy（SEM）images of N-A-S-H gels and aluminosilicate gels,proving that the geopolymer has been successfully prepared.In addition,the specific surface area of CGGP is 5.26 m²/g,and the pore size distribution of CGGP is around 10.74 nm,which is a mesoporous material.（2）The magnetic Fe₃O₄-gangue geopolymer（Fe₃O₄-CGGP）was successfully prepared by introducing Fe₃O₄ into the preparation of CGGP and comparing the effects of different loading methods on the magnetic properties of the material,and finally the chemical mixing method was selected.By comparing the effect of Fe₃O₄ loading on the phenol removal rate,the maximum phenol removal rate was 97.79%when the loading of Fe₃O₄ was 50%.The chemical composition and morphological structure of Fe₃O₄-CGGP were analyzed in combination with the characterization technique,and the results showed that Fe₃O₄ with particle size of 10-20 nm was uniformly dispersed on the CGGP surface to form Fe₃O₄-CGGP,and the saturation magnetization intensity of Fe₃O₄-CGGP reached 35.68 emu·g^-1,which indicated that Fe₃O₄-CGGP had good catalytic activity The specific surface area of CGGP increased from 5.26 m²/g to 9.42 m²/g due to the embedding of Fe₃O₄ on the surface and inside of CGGP,and the adsorption effect of the material and the increase of the specific surface area enhanced the contact between phenol molecules and·OH and improved the Fenton-like oxidation efficiency.The performance of Fe₃O₄-CGGP on the catalytic oxidative degradation of phenol by Fenton-like oxidation was investigated by single-factor experiments,which showed that the optimum pH of the reaction was 3.5,the optimum amount of Fe₃O₄-CGGP was 0.5 g·L^-1,and the optimum amount of H₂O₂ was 10 mmol·L^-1.The removal rate of 100 mg·L^-1 phenol could reach100%in 60 min under the optimal conditions.The phenol removal rate was 91.65%with good magnetic properties and stability after 5 times of use.Finally,it was found that·OH was the most important reactive oxygen species in the Fenton-like catalytic oxidative degradation of phenol.The chemical reaction rate of Fenton-like catalytic oxidation of phenol was obtained by fitting the Fenton-like kinetic equation,which was most affected by the concentration of phenol,least affected by the catalyst dosage,and less affected by the H₂O₂ dosage.（3）Based on the preparation of Fe₃O₄-coal gangue geopolymer（Fe₃O₄-CGGP）,MnFe₂O₄-coal gangue geopolymer（MnFe₂O₄-CGGP）was successfully prepared by introducing MnFe₂O₄.By comparing the effect of MnFe₂O₄ loading on the removal rate of bisphenol A（BPA）,the maximum removal rate of BPA was 91.65%when the loading of MnFe₂O₄ was 40%.The crystalline phase,morphology and structure of MnFe₂O₄-CGGP were analyzed in combination with the characterization techniques,and the results showed that MnFe₂O₄ with a particle size of 50 nm was uniformly dispersed on the surface of coal gangue geopolymer（CGGP）to form MnFe₂O₄-CGGP,and the saturation magnetization intensity of MnFe₂O₄-CGGP reached 10.96emu·g^-1,which indicated that MnFe₂O₄-CGGP has good catalytic activity and magnetic responsiveness.the specific surface area of CGGP increased from 5.26 m²/g to 5.66 m²/g due to the embedding of MnFe₂O₄ on the surface and inside,while the adsorption of the material with the increase of the specific surface area enhanced the contact between BPA molecules and·OH and improved the Fenton-like oxidation efficiency.Then,the performance of the initial concentration of BPA,initial pH,catalyst dosage and H₂O₂ dosage on the catalytic oxidative degradation of BPA by MnFe₂O₄-CGGP Fenton-like oxidation was investigated by single-factor experiments,which showed that the optimum pH of the reaction was 3.5,the optimum dosage of catalyst was 0.6 g·L^-1,and the optimum addition of H₂O₂ was 20 mmol·L^-1 at the optimum The removal rate of BPA at 50 mg·L^-1 was 100%in 60 min under the optimum conditions,and the removal rate of BPA by MnFe₂O₄-CGGP catalyst was still above 95%after5 times of use and still had good magnetic properties and stability.Finally,in combination with the quenching experiments,it was found that·OH was the most dominant reactive oxygen species in the Fenton-like catalytic oxidative degradation of BPA.The chemical reaction rate of Fenton-like catalytic oxidation of BPA was obtained by fitting the Fenton-like kinetic equation,which was most influenced by the BPA concentration,less influenced by the catalyst dosage,and least influenced by the H₂O₂ dosage.