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

With the development of the composite materials, the requirement of the modified functional composite materials was increased rapidly. Because of its advantages of abundant reserves, low prices and the stability of the physical and chemical properties, the different composite materials prepared from clays attracted extensive attention. After being modified by organic materials, the different organic functional groups can be introduced into the surface of the clay, these functional groups can form metal complexing compound with metal ions and improve the adsorption capacity of metal ions, so that the clay has been more widely used. Based on the review of the properties and the applications of montmorillonite and palygorskite, the dissertation included following contents:1. The composite materials of the montmorillonite/polypropylene thiourea were prepared to adsorb Cr⁶⁺ of the industrial wastewater and it was characterized by the methods of FT-IR, XRD, TG and SEM. The effects of pH, the amount of the adsorbent, contact time and temperature on the removal of Cr⁶⁺ were investigated. The results had indicated that the best conditions followed: the temperature was 313 K, the adsorbent amount was 20 mg and the pH was 1, the maximum adsorption capacity was 53.13 mg g^-1. Adsorption isotherm was well described by Langmuir model. The kinetic data indicated that the adsorption fitted well with the pseudo-second-order kinetic model.2. The natural palygorskite activated by 3-aminopropyltriethoxysilanes and then it was modified by epichlorohydrin and thiourea was used to investigate the adsorption behavior of Cr⁶⁺ from aqueous solutions, and the adsorbent was characterized by the methods of FT-IR, SEM, TG and EA. The changes of the parameters of pH, contact time and temperature were tested in the adsorption experiments. The results had indicated that the temperature was 303 K, the pH was 3, contact time was 90 min and the amount of the adsorbent was 10 mg, the maximum adsorption capacity was 74.63 mg g^-1. The kinetic datas indicated that the adsorption fitted well with the pseudo-second-order kinetic model. Thermodynamic parameters, such as Gibbs energy free (â–³G°), enthalpy (â–³H°) and entropy (â–³S°), were estimated. Results suggested that the adsorption process was a spontaneous process.3. A new adsorbent was synthesized by palygorskite modified by thionylchloride and N-methylimidazole which was used to investigate the adsorption behavior of Pb²⁺ ions from aqueous solutions. The adsorbent was characterized by the methods of FT-IR, SEM and TG/DTG. The effects of adsorbent dose, pH, contact time, ionic strength and temperature on the adsorption were investigated. The results had indicated that the temperature was 283 K, the adsorbent dose was 10 mg, the pH was 5, and the maximum adsorption capacity was 714.29 mg g^-1. The kinetics study indicates that the adsorption is a pseudo-second-order process. The adsorption was well fitted by the Langmuir adsorption isotherm model.4. The new adsorbent was synthesized by natural palygorskite modified by thionylchloride and 2-aminothiazole, and then it was characterized by the methods of EA, SEM and XRD. The effects of pH, contact time, temperature and selectivity of different metal ions were investigated. For Pb²⁺, Cu²⁺, and Mn²⁺, the thermodynamic curves fitted the Langmuir model, whereas experimental data for Cd²⁺ fitted the Freundlich model. At pH 5, the results showed that the Pb²⁺ had the better selectivity than other metal ions.