Study On The Removal Of Trichloroethylene In Soil And The Utilization Of Its Product

Brownfield Site caused by chlorinated organic compounds all over the world,typical chlorinated hydrocarbon contaminants,trichloroethylene(TCE),depending on the physical property as dense nonaqueous-phase liquids,are difficult to remediate by routine remediation techniques such as pump and treat methods.Nano zero-valent iron(nZVI)treatment is one of the most promising technology which can transform a group of recalcitrant groundwater contaminants encompass chlorinated hydrocarbons(CAHs).Because the ability to efficient scavenge,rapidly transform contaminants in controlled laboratory experiments,Nano zero-valent iron is currently investigated as a stabilizing amendment for contaminated soils.Moreover,depending upon the previous research,we can learn that the mechanism of removing chlorine-containing organic with zero valence iron is three possible reducing agents,Fe0,Fe2+ and [H] in the reaction system,dechlorinate CAHs through the reduction reaction.Specific to vinyl chloride such as TCE,?-reduction is the chief pathway of degradation,beside,hydroammonolysis can also occur,and the final products are ethylene and ethane which are environmentally friendly.However,previous studies have focused on solving the problem that the zero-valent iron has a strong tendency to become oxidized and aggregation,and the transport problem in soil and groundwater,and overlooked the use of reaction product..As we know,ethylene is an important material for the petrochemical industry,worldwide demand for ethylene has been growing steadily,techniques to gain ethylene such as methanol technology and methanol-to-olefin(MTO)technology was developed.What's more,it's reported that natural gas in the soil affects vegetation health,particularly ethylene,C2H4,is a well-known plant hormone auxin which plays a key role in the process of plant growth.Arabidopsis(Arabidopsis thaliana),ryegrass(Lolium perenne L.)and flax(Linum usitatissimum L.)were proven regulated by ethylene among diverse aspects of plant growth and development as fruit ripening,flower senescence,and abscission.In the present work,we choose carbon as an efficient adsorbent and suitable carrier for the excellent properties in mechanical strength and porous structures.Advantages of carbon include high conductivity,thermos-stability,corrosion-resistant,superior chemical stability and biocompatibility.In this experiment,we prepared carbon-iron materials in three different ways: one by hydrothermal method and,one use the method of high energy ball milling,and one by NaBH4 reduction,and characterized by SEM,XRD and BET.The results demonstrate that the three kinds of iron-carbon materials AC/Fe,HC/Fe,BC/Fe are successfully prepared.The result of TCE degradation experiment shows that AC/Fe,HC/Fe and BC/Fe all have good removal effect for TCE.Above 80% TCE were removed in 24 hours and the ultimate removal rate reach 100%.In addition,BC/Fe reduces TCE tend to produce more ethylene than the other two,and showed excellent adsorption on ethylene.So we select BC/Fe as the appropriate materials for the subsequent plant experiment.In the experiment,we select ryegrass(Lolium perenne L.)as object.The plant growth index and observation in cell level,showed that BC/Fe successfully degradedCE in soil,produced and stored ethylene,which affected plant growth.In group BC/Fe adsorbed ethylene treated soil and BC/Fe degradation of TCE polluted soil,the plant biomass was 117.66% and 116.30% of the blank group,present a better growth status.