Synthesis And Fundamental Separation Investigation Of Thiacalixarene Derivatives And Their Composite Materials

Substantial quantities of radionuclide strontium（Sr）are generated each year from nuclear facilities,nuclear weapon tests,and sudden nuclear accidents due to military and industrial activities.Sr was unavoidably released into natural that causing serious threat to environment and human health.Thus,the removal and analysis of Sr has become a significant environmental matter in recent years.In addition,the removed Sr have potential application in the area of industry,medicine,component,etc.The recovery of Sr from aqueous medium could to be a new channel of getting resource.Accordingly,further research for feasible processes to separate Sr from solutions is required.As a third generation supramolecule compound,calixarene can be chemically modified easily,and it shows superior thermal and irradiation stability.Thiacalixarenes not only keep the merits of classical calixarenes,but exhibit some new advantages,such as bigger cave structure,controllable structure and excellent complex ability.Therefore,thiacalixarenes have been widely used to study the recognition of metal ions.For this purpose,some calixarene derivatives and their new composite materials（thiacalixarenes-graphene and thiacalixarenes-resin materials）were synthesized and characterized.The separation behavior for Sr ions in solutions was investigated.The main contents and results are as follows:（1）Some thiacalixarene derivatives and were their new composite materials,TCAS-rGO、SCAS-rGO、SCAS-D201、SCAS-D202、SCAS-D301 were synthesized.They were characterized by FT-IR,Raman spectroscopy,XPS,SEM,EDX and TGA.The composite mechanism between thiacalixarene derivatives and graphene/resin was discussed.（2）Solvent extraction behavior ofр-tert-butylsulfonylcalix[4]arene（SCA）towards Cs（I）and Sr（II）from aqueous solutions was studied with respect to the effects of contact time,pH value,SCA concentration,nitrate concentration and temperature.The stoichiometry of metal with respect to SCA was determined to be 1:1（Cs:SC4A）and 1:2（Sr:SCA）.A possible extraction mechanism involves formation of an adjustable cavity from two SC4A molecules for the complexation of one Sr（II）ion,and the size of the adjustable cavity changes depending on the ion within an appropriate range.Irradiation stability of the SC4A and SCA/CHCl₃ was tested,the result indicates that SC4A and SCA/CHCl₃ shows efficient extraction ability when the irradiation dose was less than 5.0×10⁵ Gy.（3）The adsorption of Sr（II）onto SCAS-D201（SCAS-D202,SCAS-D301）and SCAS-rGO as a function of pH,contact time,metal ion concentration,and temperature were investigated.SCAS-D201 shows the best adsorption performance among these thiacalixarenes-resin materials and it can be reused as an adsorbent following 5 cycles of adsorption/desorption.The adsorption ability of SCAS-D201 to Sr（II）depends mainly on SCAS,while that of the SCAS-rGO depends mainly on the SCAS and oxygen-containing functional groups.The process of adsorbing Sr（II）is more suitable for pseudo-second-order kinetics model and Langmuir adsorption isotherm model.Chemical adsorption is the rate-limiting step of the adsorption mechanism.The adsorption reaction is endothermic and thermodynamic parametersΔG^o,ΔH^o andΔS^o were obtained.（4）The adsorption of Pb（II）and Cd（II）onto TCAS-rGO as a function of pH,contact time,metal ion concentration,and temperature were investigated.Results showed that the adsorption was greatly influenced by the pH.TCAS-rGO shows excellent selective adsorption for Pb（II）and Cd（II）comparing to other metals Na（I）,K（I）,Mg（II）and Sr（II）at natural pH.The adsorption reached equilibrium within 4 h and the kinetics could be described well by a pseudo-second-order model.The adsorption isotherms for Pb（II）and Cd（II）were fitted by the Langmuir model.Thermodynamic studies indicate the adsorption was a spontaneous and endothermic process in nature.The chloride and nitrate anions may have no adverse impacts on the adsorption of the target ions.The TCAS-rGO can be reused as an adsorbent following 4 cycles of adsorption/desorption.In addition,the TCAS-rGO were characterized by FT-IR and SEM before and after the adsorption of Pb（II）/Cd（II）.These new composites show superior thermal stability,preferable viscosity and excellent adsorption capacity towards metal ions.This work provides a new thought for the removal of metal ions from aqueous solutions.