Study On Microwave-enhanced Fenton-like Process Catalyzed By Modified Coal Fly Ash For Treatment Of Polymer-flooding Wastewater

The polymer concentration of the polymer-flooding wastewater is high as well as its viscosity,which is difficult to treat.coal fly ash（CFA）is a large amount of solid waste,and based on its large specific surface area and active components,in this study,under microwave enhancement,CFA was used as a Fenton-like catalyst instead of Fe2+ to catalyze H₂O₂ to treat polymer-flooding wastewater.Three methods of acid,alkali and heat were used to prepare CFA catalyst.The results show that the CFA catalyst prepared by H₂SO₄ impregnation acid modification method has the best catalytic performance.When [H₂SO₄]=6 mol/L,acid leaching time=5 h,acid/ash ratio=7:1,APAM removal rate reached 93.2%.After acid modification,the specific surface area of CFA was increased from 1.5208 m2/g to 11.4627 m2/g.The active structures such as Si-O-Si（Al）and Si（Al）-O were fully exposed,and the activity of CFA was improved.A single factor experiment was used to optimize the treatment process conditions of simulated polymer-flooding wastewater（SPW）and actual polymer-flooding wastewater（PW）.The optimal conditions are: acid-modified fly ash（ACFA）loading = 10 g/L（SPW）or 20 g/L（PW）;H₂O₂ dosage = 10 mmol/L（SPW）or 18 mmol/L（PW）;the initial p H of the solution is 3;Microwave power is 490 W;microwave enhancement time is 5 min;constant temperature reaction time = 90 min（SPW）or 50 min（PW）.APAM degradation conforms to first-order kinetic behavior,and the relationship between reaction rate constant and reactant concentration is 6)= 4355 · 0)-4724.8 · [ACFA]0.411· [H₂O₂]0.947.Correlation analysis shows that the relationship between PW and each reaction condition is closer than SPW,and the factors that have the greatest impact on the degradation rate of PAM are constant temperature reaction time.The ACFA catalysis and microwave strengthening mechanism in the microwaveACFA-Fenton-like reaction process were investigated.The results show that the heterogeneous catalytic degradation process of ACFA has a similar reaction curve as the homogeneous catalytic reaction of Fe3+,and heterogeneous catalysis plays a major role.The microwave-assisted strengthening was manifested by the fact that microwave not only accelerated the generation of ·OH,but also increased the generation path of ·OH through the synergistic effect of leaching metal elements in the ACFA.The comparison of the correlation coefficient between the microwave power,the generation of ·OH and the PAM degradation rate shows that microwave can accelerate the rapid generation of ·OH,and ·OH directly participates in the Fenton-like reaction.That is,·OH as an intermediate product is more closely related to the PAM degradation rate,and microwave helps to strengthen the Fenton-like process.This study provides an effective way for the reuse of CFA and can effectively treat polymer-flooding wastewater,which has important environmental significance and social and economic benefits.