Remediation Of Organochlorine Pesticides Contaminated Lake Sediment Using Activated Carbon And Carbon Nanotubes

Organochlorine pesticides(OCPs)are the world recognized on the environment andbiological hazards to a larger class of persistent organic pollutants.They can enter the human body through the food chain,and can accumulate in the heart,liver,kidney and other tissues,and can be discharged through breast milk.DDT and HCH are one of the most typical representatives and have been banned for years.but Due to they are difficult to be degraded in the soil,residues are still very high,causing a serious threat to agricultural production,agricultural product quality and human health.Residues of HCH and DDT in the soil are easy to be aged or solidified,which can reduce the bioavailability and extraction,but still have a great potential harm to the environment.It is a hotspot in the field of environmental science and soil science to ensure the safe and effective removal of DDT and HCH pollution in soil,and to ensure the sustainable use of land resources and the safety of agricultural production.It is very urgent and necessary to research and develop efficient and rapid treatment technology of soil contaminated by DDT and HCH.In this thesis,Sediments collected from Hunan Dongting lake were remediated.And remediation for highly contaminated sediment was investigated by quantitatively addition of organochlorine pesticide standards.Two kinds of carbon-based materials including active carbon and multi-walled carbon nanotubes were introduced to conducted different experiments.The remediation efficiencies of these two kinds of carbon-based materials were compared and evaluated for highly polluted sediments,which would provide scientific basis and technical parameters for the future development of organochlorine pesticide contaminated site remediation engineering practiceThe specific contents of this study are as follows:(1)It is scientific and reasonable to evaluate the risk of contamination in soil by using the biological effectiveness concentration,and to study the desorption constant of DDT and HCH in Dongting lake mud by adding Tenax resin.The results showed that p,p'-DDT analytical rate was the lowest,on the 30th day after the analytical concentration was 33.8%,p,p'-DDD analytical rate(i.e.68.6%)was the highest.Analytic rate in its homologue in gamma-HCH was the highest,30 days after the analytical concentration was 59.5%,the lowest concentration of 34.6%-HCH.(2)The release of different dosage of materials and the sediment in different time was investigated.The results showed that after 2%activated carbon treatment for 150 days,sediment release into the concentration of aqueous solution of HCH and DDT reduced by 97%and 92%respectively.Under the same treatment conditions,multi-walled carbon nanotubes in 150 days after treatment,the concentration of aqueous solution of HCH and DDT released from sedimentreduced 75%and 59%,respectively.(3)Semi permeable membrane(SPMDs)experiments were conducted to simulate lipid uptake of OCPs after sediments treatment.Results showed that,at the dose of 2%multi-walled carbon nanotubes treatment,the concentration in membrane extraction for HCH and DDT after 150-day treatment decreased 75%and 63%when compared to that without treatment.Nevertheless,at the dose of 2%activated carbon treatment,the concentration in membrane extraction for HCH and DDT after 150-day treatment decreased 75%and 63%when compared to that without treatment.(4)In addition,the sediments remediation efficiencies were investigated by different treatment methods(i.e.covering and mixing)using carbon-based materials.Results showed that whether activated carbon being mixed with the sediment or being covered on the sediment,sediment and water body could be separated effectively,thus reducing released HCH and DDT from sediments.After 45 days of activated carbon treatment,the relative respectively.(5)A series of experimental results demonstrated that the adsorption efficiency of activated carbon was better than that of multi-walled carbon nanotubes.The reason was mainly thatactivated carbon had greater surface area than multi-walled carbon nanotubes,thus leading to effective adsorption for organic chlorine pesticides.Furthermore,adsorption effect of activated carbon was remained after 150-day use.