| As an important fresh water resource,groundwater is seriously polluted by the development of industry and human activities.Polycyclic aromatic hydrocarbon(PAHs)is a typical organic pollutant in groundwater,and its remediation technology has been widely concerned by the international community.In this paper,phenanthrene was selected as the target pollutant,and ozone,hydrogen peroxide and ozone/hydrogen peroxide were used as oxidants to explore the effects of time,temperature,pH,O3 concentration,H2O2 concentration,substrate concentration and other factors on phenanthrene degradation.A degradation kinetic model was established,and the products of phenanthrene degradation by O3 were identified by GC-MS.Based on the above experimental results,an indoor groundwater simulation device was built to study the treatment effect of catalysis and electrolysis on the actual groundwater containing phenanthrene and monitor the physical indicators of the treatment process.This paper has great theoretical guidance and practical significance for in-situ groundwater remediation technology based on high-efficiency catalysis and electrolysis.The main conclusions are as follows:(1)The removal rate of phenanthrene was over 99%after 60 min in the O3 degradation system at 20 L/min flow rate and 2 mg/L concentration.The degradation rate of phenanthrene is the highest when the temperature of the system is 35??40?,the suitable pH is 7?9,the increase of O3 concentration is helpful to improve the degradation rate of phenanthrene,and the reaction process accords with the first-order kinetic equation.The degradation of phenanthrene mainly depends on the direct oxidation of O3,followed by the indirect oxidation of OH.It was found by GC-MS that diphenyl-2,2-diphenylaldehyde,dibutyl phthalate and other substances were formed during the degradation of phenanthrene by O3.(2)After 12 hours,the degradation rate of phenanthrene was only 36%?55%in H2O2 degradation system,and the degradation rate did not increase significantly with the increase of reaction time.The degradation rate was the highest when the temperature was 25??30?,and pH was 3.The degradation efficiency of phenanthrene increased first and then decreased with the increase of H2O2 concentration.Compared with O3 system,the degradation rate of phenanthrene in O3/H2O2 system can be increased by adding H2O2.When the concentration of H2O2 is 19.6 mmol/L,the degradation rate of phenanthrene in one minute is 22%higher than that in O3 system.However,when the concentration of H2O2 is more than 49 mmol/L,the excess H2O2 will react with O3,and the degradation of phenanthrene will be inhibited obviously,and the reaction rate constant is less than O3 system.The optimum temperature of phenanthrene oxidation in O3/H2O2 system is 30?,and the optimum pH is 7.The process of phenanthrene reduction in H2O2and O3/H2O2 systems is in accordance with the first-order kinetic equation.(3)The underground water simulation device is built by water distribution tank,electromagnetic flowmeter,inflow peristaltic pump,visualization box and other equipment.When a single catalysis and electrolysis is used in the actual underground water simulation device,the removal rate of phenanthrene in the water sample is 35.4%?41.6%after 2 hours of treatment.During the whole process of oxygenation,there is no obvious change in the system temperature,pH and conductivity,and the dissolved oxygen decreases from 7.5 mg/L to 3.8 mg/L The redox potential decreased from-13.2 mV to-337 mV,so the Catalysis and electrolysis has a good prospect in the field of groundwater remediation. |
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