Efficacy And Mechanism Of β-Cyclodextrin Functionalized Materials On Remediation Of Lead And BPA In Soil

The prevention and control of soil pollution is an urgent scientific problem to be solved on a global scale.Among them,the heavy metal lead（Pb）and the estrogen bisphenol A（BPA）are two common pollutants in soil,and their existence can cause serious damage to soil and human health.Therefore,it is urgent to explore ways to repair Pb and BPA pollution.Among many remediation materials,biochar and sodium alginate are widely used in the remediation process of Pb and BPA pollution due to their environmentally friendly properties.However,unmodified biochar and sodium alginate are not ideal for pollutant removal.β-Cyclodextrin is regarded as one of the ideal modifiers due to its special cavity structure,and its hydrophilic outer surface and hydrophobic inner cavity can form non-toxic compounds with heavy metals and estrogens,which can effectively remove soil of Pb and BPA.In this study,two repair materials,β-cyclodextrin-functionalized biochar(BC_MW-β-CD)andβ-cyclodextrin-functionalized magnetic sodium alginate(MSA_MW-β-CD)were prepared by microwave-assisted method.The adsorption experiment explored the effect of different influencing factors on the adsorption of Pb and BPA by the two materials,and analyzed the removal mechanism of Pb and BPA.In addition,the remediation efficiency of MSA_MW-β-CD on Pb and BPA in soil was explored and its repeated regeneration performance was analyzed.The main research contents and achievements are as follows:（1）β-cyclodextrin-grafted biochar can be prepared in only 15 min by microwave-assisted one-pot method,which is named BC_MW-β-CD.Moreover,β-cyclocyclodextrin-functionalized magnetic sodium alginate can be prepared by one-pot method using low-power microwave irradiation for 30 min and named MSA_MW-β-CD.The effects of pyrolysis temperature and synthesis method on the adsorption performance of BC_MW-β-CD were explored.In addition,the effects of preparation time and the ratio of magnetic sodium alginate to citric acid on the adsorption performance of MSA_MW-β-CD were explored.Fourier transform infrared spectroscopy,X-ray diffraction analysis and other characterization methods confirmed thatβ-cyclodextrin was successfully grafted onto biochar and sodium alginate.（2）The adsorption properties of BC_MW-β-CD and MSA_MW-β-CD were studied by single-factor batch adsorption experiments.Both of them showed excellent p H adaptability and stable adsorption effect on lead and bisphenol A in a wide p H range;the adsorption of Pb（II）and bisphenol A by BC_MW-β-CD reached the adsorption equilibrium at 20 and 30 min,respectively,and MSA_MW-β-CD reached the adsorption equilibrium at 30 and 15 min,respectively.Both of them can spontaneously react and release heat at different temperatures,and after 5 rounds of adsorption-desorption experiments,they still maintain excellent stability and excellent adsorption performance.The adsorption capacities of BC_MW-β-CD for Pb and BPA were 240.13 and 209.20mg/g,and the MSA_MW-β-CD theoretical adsorption capacities for Pb and BPA were 369.03 and208.36 mg/L,respectively.（3）The remediation effect of MSA_MW-β-CD on Pb and BPA in soil was explored.The results showed that MSA_MW-β-CD had the best remediation effect in neutral soil.Compared with other remediation agents,MSA_MW-β-CD showed excellent remediation effect on Pb and BPA under different soil moisture content conditions.In addition,the repair effect of the 5%MSA_MW-β-CD experimental group was significantly better than that of the 1%and 3%experimental groups.MSA_MW-β-CD decreased the unstable fraction of Pb by 7.41%,and the recalcitrant fraction increased by 10.34%.In addition,MSA_MW-β-CD can be effectively magnetically separated from soil,and after three cycles of regeneration,MSA_MW-β-CD can reduce the contents of Pb and BPA in soil by 56.30 and 0.78 mg/g,respectively.（4）The removal mechanism of Pb and BPA by BC_MW-β-CD and MSA_MW-β-CD was explored by means of XPS and other characterization methods.The results showed that the binding of Pb to BC_MW-β-CD mainly through complexation and electrostatic interaction,The elimination of BPA is mainly through the interaction of host-guest molecules andπ-πstacking.Ion exchange,pore deposition,complexation and electrostatic attraction were all involved in the adsorption of Pb by MSA_MW-β-CD;besides,MSA_MW-β-CD immobilized BPA through host-guest interaction andπ-πstacking.