Study On The Migration And Transformation Of Pentachlorophenol In The Loess Soil And Treatment Of Pentachlorophenol Wastewater

Due to the significant characteristics:long-term remains,bioaccumulation,semi-volatilized and hightoxicity,Pentachlorophenol(PCP)has been attributed to the Priority Pollutants and Persistent OrganicPollutants.In the west of China,the Loess possesses a great share in the land distributions,thus the soilcontaining Loess is an important factors for the utilization of agriculture,forest,animal husbandry,urbanconstruction and industrial development.In this way,more and more attentions have been paid to theresearches of pentachlorophenol and its sodium salts(PCP-Na)in Loess,such as the migration,the impacton the groundwater,and the management methods of pentachlorophenol and its sodium salts(PCP-Na)inXi'an Loess.From our points,those subjects have very important theoretical and practical values,forinstance,revealing the adsorption and migration laws of pentachlorophenol in the Loess,announcing theinfluence degree of pentachlorophenol and its sodium salts on the groundwater,seeking for the ways andmeans to remove pentachlorophenol and its sodium salts from water,grasping migration and distributionlaws of PCP / PCP-Na,evaluating the environmental hazards,reducing the pollution of groundwater,protecting the groundwater resources and treating pentachlorophenol wastewater,etc.In the present thesis,the structures,properties,resource and harm of PCP / PCP-Na have beengleaned,the adsorption and migration of pentachlorophenol and its sodium salts in the soil / sediments hasbeen reviewed.The latest developments of treatment of pentachlorophenol and its sodium salts wastewaterhave been summarized.To our the best knowledge,The several pivotal subjects related with those field arefurther pay close attention to by using the Loess of Xi'an,the detail items includes:theadsorption/desorption properties and laws of PCP-Na in the Loess have been ascertained by combination ofstatic and dynamic method,the curves of adsorption thermodynamic and dynamic have been detected anddetermined.the migration transformation mathematical model of PCP-Na in the Loess and its modelparameters have been obtained,and the result showed that the model parameters have a good cohererencewith the experimental value,which further verify the validity of migration transformation mathematicalmodel.Besides,the adsorption and desorption of PCP-Na wastewater on the activated carbon,HDX-8 resin,D311A anion exchange resin have been investigated,moreover,adsorption kinetic and thermodynamic alsohave been determined.In addition,by choosing the resin chelated by Fe(â…¡)and Fenton reagent andFenton agent,the degradation of PCP-Na wastewater by combination of Fenton method and photocatalytic have been studied.The optimal reaction condition have been attained.Those routes solve the severaldifficult problems,i.e.,lower reactive efficiency;rub on the analysis of PCP-Na wastewater and bringingthe external pollution.Correspondingly,the treatment processes of PCP-Na wastewater have been designed.Those results can facilitate the protection of groundwater and the treatment of PCP-Na wastewater.Certainly,some important and practical significance of research conclusions have been attained.1.The adsorption of PCP-Na in the Loess abides by the Elovich equation and the tow-parametersequations.Thereinto,the constant of adsorption quantity is 53.9mg/kg and the adsorption rate is 21.5mg/(kg.h).2.The adsorption of PCP-Na in the Loess belongs to an exothermal spontaneous reaction,and themain force can be attributed to the hydrogen bond.Adsorption isotherm can be described with Freundlichequation and Langmuir equation,respectively.3.The Loess soil has not a function for the enrichment of PCP-Na,and the PCP-Na penetrates theLoess soil easily.Inevitably,the groundwater will be contaminated by the PCP-Na.4.The migration of PCP-Na has been affected by the hydrodynamic diffusion and adsorption/desorption simultaneously,but the influence of degradation can be ignored.Additionally,It has been foundthat adsorption abides by the Herry equation:q=K_dC,thereinto,the adsorption constant K_d=0.0847cm³/g,the retard factor R=1.46,the diffusion coefficient D=0.00466m²/d.Moreover,the results determined formthose modes has a well coherence with the experiments",which indicated that the diffusion modes can beused to simulate the migration of PCP-Na in The Loess soil well.5.The most effective adsorbent for the treatment of PCP-Na wastewater by adsorption method isD311A ion exchange resin.The main merits include the faster adsorption rate,the larger adsorptioncapacity,the quick desorption procedure,the higher desorption efficiency and slow penetrating rate.6.The illumination time,concentrations of H₂O₂,resin chelated by Fe(â…¡),Fe(â…¢)and the initialconcentration have an effect on the degradation of PCP-Na.7.In the presence of catalysts of resin chelated by Fe(â…¡)and Fenton reagent,the optimal conditionfor the degradation of PCP-Na include 0.2g resin chelated by Fe(â…¡);24μg/ml H₂O₂;16μg/ml PCP-Na;and 150min illumination time,and the degradation efficiency attained 94.2%.The sensitivity orders ofthose factors are:illumination time＞quantity of resin chelated by Fe(â…¡),Fe(â…¢)＞the initial concentrationof PCP-Na＞the initial concentrations of H₂O₂. 8.The concentration of Na⁺,K⁺,Mg²⁺,Cl^-,SO₄^2-more than 50 times of PCP-Na have not effect onthe degradation efficiency.However,the concentration of Zn²⁺,NH₄⁺,NO₃^-just 5 times of PCP-Na willhave an obvious effect.9.Fe(â…¡),Fe(â…¢)have a similar effect on the photo-catalytic degradation of PCP-Na.