Study On The Treatment Of Toxic And Organic Point-Resource Pollution In The Soil By Fenton Reagent

When the organic chemicals are deposited or transported,it is hard to avoid environmental contamination accidents,such as oil leaking,happening,which have caused a mass of toxic organic pollution to flow into the soil.To solve the pollution accidents in time and eliminate the toxicity right in the accident site has become the key to avoid the extending of the hidden trouble.In this thesis,the soil polluted by PCP was treated by Fenton reagent process,and varing effects were investigated.Continuous stiring reactor was used to treat the high concentrate PCP and the optimal condition was obtained in this paper.Fast detection of PCP in the soil has been found in this thesis.Based on the principle of the reaction of NaOH with PCP and formation of PCP-Na, water-insoluble of PCP is transformed into water-soluble salts(PCP-Na) to realize the extraction of PCP from the soils.Ultraviolet spectrophotometric method was adopted to determine PCP at 319nm.The extraction condition for PCP was optimized with the stirring rate of 300r/min,extraction solution at pH＞12.5,the ratio of soil/liquid=1/10(g/mL) and extraction time of 20 min.The sensitivity of the method is 2μg/mL for PCP with recovery of 91.2%～108.1%.This method is adapted to treat accidental point-resourced pollution in the soil and it has been used in this thesis to detect PCP.The preliminary operating conditions were determined by orthogonal experiments,and each effecting factor was analyzed according to preliminary operating conditions.The optimal operating conditions were determined by researching effecting factors,which is H₂O₂:Fe²⁺=10:1,PCP:H₂O₂=1:531,pH=3. And up to 93.2%PCP is degraded in this condition.The effects of PCP degrading of Fenton reagent and Fenton-like reagent were contrasted.And each effecting factor was analyzed to get the optimal operating conditions of the Fenton-like:H₂O₂:Fe³⁺=40:1,pH=3.And up to 70%PCP is degraded in this condition.By contracting the effect of this two catalyzers on the system,we got that Fenton reagent is adpt to treat the PCP polluted soil with the high concentration in short time.Stablizer,KH₂PO₄,was also used in this thesis to find whether it effect the degragation.We found that stabilizer can extend the reaction time.Accordingly PCP could have more time to react with·OH,which could enhance the PCP degradation.The addition of KH₂PO₄ can not only control the speed of reaction,enhance the degradation,but also can rich the soil,which is propitious to soil chemical restoration.The continuous stiring reactor was used to treat the high concentrate PCP. Through the analyzing of the different process parameter,and the optimal process condition was determined.We got that the useful volume of the reactor is 1L,the optermal condition is pH=3,soil:water=1:1(g:L),H₂O₂:Fe²⁺=10:1.The way of adding Fenton reagent:0mL～300mL:20mL/time;300mL～400mL:50mL/time; 400～600mL:100mL/time;600～1000:200mL/time.The internal is 10min/t and the residence time is 200min.In this condition,up to 80%PCP was degraded. Actually when we increase the soil,the dose for each time should be increased with the same time.In this condition,the relation of polluting extent and the dose of the Fenton reagent was discussed and got the linearity equation: y=0.0073x+2.9 that could be used to estimate the the dose of the Fenton reagent by the PCP concentration of the soil.And when we increase the soil to treat,the dose should be increased with the same time.By the economical feasibility analysis on Fenton reagent process in treating PCP polluted soil,it was pointed out that this method in treating point-resource polluted soil was pratical.The investigation of this thesis laid the thery foundation and offered the useful parameters for Fenton reagent in treating point-resource polluted soil accident.The result of this paper could give the theoretic foundation and experiment laws to treat the point resource pollution of the toxical organic chemical of the soil in future.