Preparation Of Thiacalixarene Modified Bentonite And Research On The Adsorption Of Heavy Metals

This paper used supramolecular receptors of thiacalixarene as the activecomponent,and loaded it with the electrostatic interactioninto into the bentonitemodified by surfactant(CTMAB).Thus,a new type of adsorption materials which isthiacalixarene modified bentonite for water pollutants was prepared.Through thecharacterization methods of Scanning electron microscope (SEM),IR Spectrumand andThe particle size distribution of bentonite and thiacalixarene-loaded bentonite.At thesame time,we can show that the thiacalixarene was not easy to fall off from the surfaceof thiacalixarene modified bentonite through the24hours oscillationexperiment.We can come to the conclusion that the thiacalixarene can stronglycombination on the surface of bentonite.A series of heavy metal adsorption experimentsshow that thiacalixarene modified bentonite to the removal of Cu2+and Pb2+isobviously better than the effect of the bentonite.In this paper,the adsorption capacities of the thiacalixarene modified bentonitetoward Cu2+and Pb2+ions were investigated by removal rate, batch adsorption factors,the adsorption kinetics,the adsorption isotherms and thermodynamics. The resultsshowed that the thiacalixarene modified bentonite has an obvious adsorption removalefficiency to low concentration of heavy metal ions. At25°C, the equilibriumadsorption capacities were0.29mg/g and0.15mg/g for Cu2+and Pb2+ions respectively,when the pH value is6.5, initial concentration of heavy metal ion2mg/L,dosage ofthiacalixarene modified bentonite0.15g/L, time of the reaction2h.The adsorptionkinetics studies showed that thiacalixarene modified bentonite were conformed to thepseudo-second-order kinetics model,and the limiting step of adsorption process waschemical adsorption.We can show that the thiacalixarene modified bentonite to theadsorption of Cu2+and Pb2+was conducted in three stages from the result of internaldiffusion of particle.The first stage was mainly from the Cu2+and Pb2+ions spreadaround the surface of thiacalixarene modified bentonite;The second stage was diffusion in the granules,spread of the Cu2+and Pb2+ions to the inner layer of the thiacalixarenemodified bentonite;The third stage was the adsorption equilibrium state.The adsorptionof Cu2+and Pb2+ions onto the thiacalix[4]arene modified bentonite was fitted better tothe Freundlich isotherm,and the whole adsorption process were both have physicaladsorption and chemical adsorption.Through the thermodynamic parameters were foundthat thermodynamical enthalpy change ΔH0and ΔS0were positive, We can infer that theadsorption reaction was the endothermic reaction process and the effect warming;Inaddition, the Gibbs free energy change ΔG0were negativeas with the increase oftemperature,it showed that the thiacalixarene modified bentonite for Cu2+and Pb2+ionswas a spontaneous process, and heavy metal ions were more easily adsorbed on thethiacalixarene modified bentonite.