| Due to the high content of organic matter and complex components,the membrane concentrate cannot achieve the ideal treatment effect with a single treatment method.Therefore,it needs to be combined with other processes to improve the treatment effect and meet the discharge standards.An experimental study on the treatment of landfill leachate membrane concentrate by a three-dimensional electrolysis-Fenton combined process was carried out in this paper.Firstly,the optimal anode,cathode and particle electrode were selected for the three-dimensional electrolytic system.The treatment effect of three-dimensional electrolysis and three-dimensional electrolysis-Fenton method was compared by single factor experiment.The response surface method was used to optimize the four influencing factors(voltage,pH,plate spacing and ferrous dosage),which affected the treatment effect of membrane concentrate.The degradation mechanism and process of three-dimensional electrolysis-Fenton method were further investigated by a free radical trapping experiment,UV-visible light analysis,three-dimensional fluorescence analysis(3D-EEM)and gas chromatography-mass spectrometry(GC-MS).The main conclusions were as follows:(1)The results showed that the DSA electrode(Ti/RuO2-IrO2)for the anode and the graphite electrode for the cathode had the best removal effect on the COD of membrane concentrate.The particle electrode selected activated carbon and silicone resin-coated activated carbon(according to 2:1 mixing),the removal effect of COD of membrane concentrated solution was the best,reaching 64.98%,12.27%and 8.66%higher than that of activated carbon,activated carbon and quartz sand mixed particle electrode,respectively.(2)Through the single factor experiment,the optimal experimental conditions of three-dimensional electrolysis and three-dimensional electrolysis-Fenton method were obtained,respectively,and the membrane concentrate was treated under their respective optimal conditions.The results showed that the three-dimensional electrolysis-Fenton method had a better treatment effect,and the removal rates of TOC and UV254 were 18.19%and 40.91%higher than three-dimensional electrolysis,respectively.(3)Based on the single factor experimental results,the four influencing factors of voltage,pH,plate spacing and ferrous dosage were selected for optimization.The quadratic polynomial model was established based on the experimental results,with P<0.0001 and R2=0.9653.The results showed that the model had good correlation and accuracy.According to the P test value of each factor and the pairwise interaction between the factors in the variance analysis,the relative relationship between the four influencing factors on the response value(TOC removal rate)was as follows:voltage>ferrous dosage>pH>plate spacing;The optimal experimental conditions predicted by the model for three-dimensional electrolysis-Fenton method were as follows:When the voltage was 14.06V,the pH was 3.03,the distance between the plates was 10cm,and the dosage of ferrous was 0.9 mmol/L,the predicted TOC removal rate was 60.34%,while the actual TOC removal rate was 59.65%.The relative error was only 0.69%,indicating that the established model had an excellent prediction effect.(4)The free radical capture experiment was carried out,and the results showed that the contribution of hydroxyl radical accounted for about 57.58%in the process of degradation of pollutants in the three-dimensional electrolysis-Fenton system,playing a leading role.(5)Analysis by UV-VIS spectrum,three-dimensional fluorescence spectrum,and gas chromatograph-mass spectrometry showed that humus organic pollutants accounted for 85.56%of the concentrated membrane solution.After treatment by the three-dimensional electrolysis-Fenton process,macromolecular organics such as siloxanes,alkane derivatives and aromatic hydrocarbons can be effectively degraded and converted into small molecular substances.Improve the biodegradability of membrane concentrate. |
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