Preparation Of Mercapto-β-cyclodextrin And The Enhanced Remediation Of Co-contaminated Soil With Lead And Phenanthrene

With the rapid industrialization and urbanization,a large number of toxic and hazardous were discharged into the soil,soil pollution has become more serious.In the present,the combined contaminations has become a common phenomenon of soil pollution.Phytoremediation is widely viewed as an green technology used to deal with heavy metals and organic compounds from the polluted soils,which is also the current hot research field.In this research,the treatment effect of enhancing phytoremediation by Mercapto- β- cyclodextrin with Pb-PHE co-contaminated soil as the research object.The main contents results are summarized as follows:1.Mercapto- β- cyclodextrin(TCD) with high water solubility was obtained was synthesized with L-cysteine and epichlorohydrin under alkaline condition.The infrared spectra showed that amino groups,carboxyl groups and mercapto groups were grafted to molecular scaffold of β-CD, which results in improvement of the water solubility of β-cyclodextrin. The results from ultraviolet spectrum showed that TCD included phenanthrene with the inner cavity of TCD and coordinated with lead through the amino groups,carboxyl groups and mercapto groups.2.The solubilization experiments showed that the TCD has obvious solubilization for phenanthrene.When the concentration of TCD was 30 g/L, solubilization multiple of phenanthrene can reach 25 times.the solubilization multiple of TCD for phenanthrene was continuedly increased with increasing the concentration of TCD.The solubilization experiments showed that the TCD has obvious solubilization for lead.When the concentration of TCD was 20 g/L,the equilibrium concentration of lead was about 1938mg/L.The solubilization experiments under the coexistence of phenanthrene and lead carbonate indicated that the inclusion of phenanthrene and coordination with lead by TCD occur in different parts of the molecular structure of TCD,furthermore,the two processes can performed simultaneously without disturbing each other.3.The desorption process of TCD for phenanthrene and lead in co-contamination soil followed the pseudo-second-order rate equation.It was beneficial to the removal of phenanthrene and lead in co-contamination soil by raising the initial concentration of TCD.The desorption efficiency of the TCD for phenanthrene in co-contamination soil decreased with increasing p H,But the result of lead was the opposite.To raise temperature could improve the removal of phenanthrene in co-contamination soil,however,it did not affect the desorption of lead basically.And the removal efficiency of TCD for phenanthrene and lead in co-contamination soil is higher than that of β-CD and CMCD.4.The tolerance of plants to TCD experiment showed that in some concentration range TCD could promote the growth of plants,but high concentration inhibited the growth of plants.A pot experiment was conducted to investigate the effects for enhanced phytoremediation of Pb-PHE in co-contaminated soil by Ryegrass with application of TCD.The results showed that the removal of phenanthrene and lead in co-contaminated soil by Ryegrass was better,as compared to the control.In addition,The SCFs and TCFs value of phenanthrene were respectively 1.25~2.45 and 1.0~2.33 times higher than that of the control groups by Ryegrass with applying TCD at the same pollution levels.The SCFs value of lead was significantly higher than that of the control without TCD treatment, and the TFs is slightly higher than that of control group.The preceding results indicated that TCD could enhance the effects for phytoremediation of Pb-PHE in co-contaminated soil by Ryegrass.