Study On The Inclusion Behavior Of ?-cyclodextrin Derivatives And Their Adsorption Of Thorium

Cyclodextrin(CD)is a kind of macromolecular compounds with "external hydrophilic,internal hydrophobic" structure,which can be selectively coated with various inorganic,organic and biological molecules to form hos-guest complexes or supermolecular species in order to improve the physicochemical and biological properties of the guest molecule,solubility,thermal stability,binding ability,bioavailability and so on.Nowadays,many researchers have tried to synthesis different kinds of CDs inclusion complexes,and they are widely used in the fields of environmental science,life science,food science pharmacy and biology.In this work,the inclusion complex prepared by ?-naphthylacetic acid and modified ?-cyclodextrins,the inclusion behavior and adsorption performance were investigation.The main work content were shown as following :1.The supermolecular chemistry,the influencing factors for the formation of cyclodextrin inclusion complexes,the determination of inclusion stability constants and the determination of inclusion ratios were briefly described.2.The inclusion complex(OTs-?-CD@NAA)of OTs-?-CD and?-naphthylacetic acid(NAA)was synthesized.The inclusion complexes were characterized by infrared spectroscopy,then the inclusion behavior of OTs-?-CD and NAA was studied by ultraviolet spectroscopy.The formation of new solid phase was confirmed by thermogravimetric analysis.Finally,the inclusion mode between host and guest is analyzed by nuclear magnetic resonance(NMR)hydrogen spectroscopy.This method is feasible,simple in operation and environmentally friendly in practice.3.OTs-?-CD@NAA inclusion complex as a sorbent was synthesized for adsorption of low concentrations of thorium from aqueous solutions.The effects of p H,reaction time,initial concentration of Th(?)ions,and temperature on the adsorption behavior of Th(?)were investigated by static adsorption.The results showed that the maximum adsorption capacity was 13.59 mg / g when p H = 2.5,t = 30 min,C0 = 30 mg/L,T = 20 ?.At the same time,the selective adsorption experiments showed that OTs-?-CD@NAA had a certain selectivity for the adsorption of Th(?).4.The experiments were designed by Box–Behnken design combined with response surface methodology.The adsorption parameters of p H value,contact time,initial concentration were used as the independent variables and their effects were investigated on the Th(?)adsorption capacity.Second-order polynomial regression models were derived and analysis of variance was utilized to judge the adequacy of the chosen models.The maximum Th(?)adsorption capacity(12.75 mg/g)was achieved under the following conditions: p H = 2.5,t = 35 min,C0 =30 mg/L.Prediction of models was in good agreement with experimental results.The experimental adsorption kinetic data followed a pseudo-second-order equation with the correlation of 0.9996,that is,both chemical adsorption and physical adsorption exist,and the chemical adsorption process is the dominant one.The obtained equilibrium isotherm data were fitted well with Langmuir model(R2 = 0.9944)in the concentration range considered.It is indicated that monolayer adsorption dominates.The thermodynamic parameters(?H0 < 0,?S0 < 0,?G0 < 0)indicated that the adsorption process was exothermic and spontaneous.OTs-?-CD@NAA before and after adsorption of Th(?)were characterized by FTIR,SEM and BET.This research hope to provide a useful reference for future treatment of waster-water.5.Using ethylenediamine-?-cyclodextrin(en-?-CD)and NAA as raw material,a novel inclusion complex(en-?-CD@NAA)was synthesized.The molecular recognition performance,stability constant,thermodynamic and solubilization between host and guest were studied.The stability constant and inclusion ratio between host and guest were measured by UV-vis spectrometric titration,and the solubilizationmultiple was calculated by phase solubility method.The structure and properties of the inclusion complex were characterized by FTIR,TGA,XRD and elemental analysis.The NAA naphthalene ring was successfully embedded into the cavity of ?-CD by 1H-NMR.To rationalize and confirm the experimental results,we used the docking technique and molecular dynamics simulation to predict the possible orientation of NAA inside the en-?-CD as well as the stoichiometry of the complex formed.The stoichiometry of the inclusion complex was 1:1 and the stability constant(KS)value was found to be 2511 M-1 at 293 K.Molecular thermodynamic parameters indicated that the spontaneous and exothermic nature of the process.It shows that the formation of inclusions between host and guest is mainly driven by enthalpy.The in vitro dissolution rate and dissolution rate of the inclusion complexes were significantly increased compared to the original drug.This study provides new ideas for the effective use of NAA in agriculture and medicine in the future.