Microwave Preparation And Properties Of Grafting Chitosan Adsorbents

Chitosan,with wide application,is a kind of natural polymer materials prepared from chitin. The present studying emphases were concentrated on chemical decorating of chitosan. After decorating, the derivatives with different configuration and performance were prepared. Nowadays, many researchers have focused on its enormous potential in the fields of application. In this work, the novel chitosan-based adsorbents was synthesized under microwave irradiation, and their adsorption properties were investigated. The details were showed as follows:(1) A novel adsorbent (CTSS) was prepared via the reaction between epichlorohydrin O-crosslinked chitosan and ethylenediamine grafted under microwave irradiation. The chemical structure of this new polymer was characterized by infrared spectra analysis, thermo gravimetric analysis, X-ray diffraction analysis and surface morphology analysis. The adsorption of CTSS on Pb²⁺and Cu²⁺ was investigated. The results demonstrate that CTSS has higher adsorption capacity than chitosan. The maximum adsorption capacities for Pb²⁺ and Cu²⁺, with initial concentrations of 0.01 mol.L^-1 at pH 5, are 234.9 and 152.2 mg.g^-1, respectively. The adsorption follows the pseudo-second-order kinetics. The isotherm adsorption equilibria for Cu²⁺ is better described by Langmuir isotherms, but for Pb²⁺ is better described by Freundlich isotherms.The adsorbent can be recycled. These results have important implications for the design of low-cost and effective adsorbents in the removal of heavy metal ions from wastewaters.(2) Under microwave, chitosan was graft polymerized with acrylic acid and crosslinked with glutaraldehyde to produce the crosslinking chitosan - grafted - poly acrylic acid(CCTS-AA). The chemical structure of this polymer was characterized by surface morphology analysis, infrared spectra analysis, thermo gravimetric analysis and X-ray diffraction analysis. The effects of various variables, such as pH, adsorption time and initial concentration, on the adsorption of Pb²⁺, Cu²⁺ and Ni²⁺ by CCTS-AA were investigated. The results demonstrated that the maximum adsorption capacity was found at pH=5 for Pb²⁺,Cu²⁺.and Ni²⁺ .The adsorption process followed the pseudo-second-order kinetics and the monolayer coverage of the adsorbents . The best interpretation for the equilibrium data was given by Langmuir isotherm and the maximum adsorption capacities for Pb²⁺, Cu²⁺ and Ni²⁺ were 176.9, 157.1 and 85.48 mg.g^-1, respectively.(3) A novel adsorbent (TU-CTS)was prepared via the reaction thiourea grafted chitosan under microwave irradiation. The structure of product was characterized by infrared spectra analysis, thermo gravimetric analysis and X-ray diffraction analysis. Various factors affecting the uptake behavior such as contact time, pH and initial concentration of the metal ions were investigated. The maximum adsorption capacities for Pb²⁺and Cu²⁺, with initial concentrations of 0.02 mol.L^-1 at pH 5, are 284.9 and 141.4 mg.g^-1, respectively. The adsorption follows the pseudo-second-order kinetics. The isotherm adsorption equilibria are better described by Langmuir isotherms.The above novel chitosan derivatives have higher adsorption capacity for heavy metal ions. These modified chitosan adsorbents would have potential applications in wasterwater treatment.