Study On The Preparation And Adsorption Properties Of Modified Palygorskite For Heavy Metal Ion

With the development of functionalized and composite materials, the requirement of modified inorganic materials was increased rapidly. As palygorskite clay is abundant, low cost, in addition, possess stable physical and chemical properties, the clay modified with various methods and different modifier meet the requirements of different areas. Palygorskite surface can introduce different organic functional groups, these functional groups can chelate metal ions and improve the adsorption capacity of metal ions, so that palygorskite has been more widely used. Based on the review of the properties and the applications of palygorskite, the dissertation included following contents:1. Functional palygorskite was prepared from purified palygorskite and characterized by the method of IR and element analysis. The exchange between ammonium salt containning hydroxyl and Ca2+, Mg2+ of palygorskite layer increased the number of -OH, NH2-(CH2)3-Si(OMe)3 was connected to the surface of palygorskite by dehydration with -OH. After dehydration, functional groups with the chelating ability were introduced by the reaction between Carbon disulfide and Amino group.the adsorption ability of modified palygorskite for Cu(II) was investigated. The influences of the pH, contact time, concentration of Cu(II) and temperature on the adsorption were discussed. In addition, the article discussed the adsorption mechanism of palygorskite and modified palygorskite for Cu(II).2. Palygorskite (PGS) was modified with aqueous poly(vinyl alcohol) (PVA) to obtain hybrid adsorbent of PVA/PGS. It was characterized by the methods of TG, SEM and FT-IR. The adsorptions of Cu(II) ions from aqueous solution with PGS and PVA/PGS were studied. The effects of acidity, contact time, initial concentration of Cu(II) ions and temperature were investigated. At pH 6 and with initial Cu(II) concentration of 100 mg/L, PVA/PGS can achieve a maximum adsorption capacity of up to 43.2 mg/g (in comparison with 27.5mg/g for PGS). The adsorption process is correlated with the pseudo-first and second-order kinetic model and Intraparticle diffusion model. The isotherms were simulated by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. The thermodynamic parameters, such as the change of free energy, enthalpy and entropy were also calculated.3. Amidoxime palygorskite was prepared by graft copolymerization. PVA has strong adhesive capacity to the oxide surface with the -OH groups. After palygorskite was modified with poly(vinyl alcohol)(PVA), the composite material was introduced the polymer containning cyano functional group, The cyano functional group was reduced to amidoxime in the hydroxyl ammonium hydrochloride solution. In addition, the article discussed the adsorption mechanism of palygorskite and modified palygorskite for Cu(II). When the pH value of about 6, adsorption capacity of amidoxime palygorskite for Cu (II) can reach the largest. Kinetic experiments show that the adsorption reach equilibrium when the adsorption time is 70min, the adsorption process is correlated with the pseudo- second-order kinetic model. The higher linear regression constants of langmuir adsorption model show that Adsorption process is monolayer adsorption.4. Palygorskite was modified with silane couple agent, Amino group and methyl acrylate occurs Michael reaction, after that, ethylenediamine can occur aminolysis reaction with Ester. the adsorption results of adsorbent for Pb(II) as follows: adsorption capacity of palygorskite functionalized by dendrimer-like polyamidoamine for Pb (II) can reach 63.54mg/g (in comparison with 31.5mg/g for PGS), When the pH value is about 6 and the metal ion concentration is 100 mg/L. The adsorption process is correlated with the pseudo-first and second-order kinetic model and Intraparticle diffusion model. The isotherms were simulated by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models.