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

Heavy metal is a kind pollutant with high toxicity in ecological environment.Some dissolved heavy metal ions can be enriched in aquatic food chains, enter intohuman bodies through aquatic products, and thus brings about serious poisoning tohuman beings. Up to now, some methods including oxidation-reduction, chemicalprecipitation, ion exchange, electrolysis and membrane filtration, are used to removeheavy metal ions in water. However, these methods have some disadvantages, such ashigh running cost, cumbersome operation, and easy to cause secondary pollution. Onthe other hand, they are mainly used to remove heavy metal ions with highconcentration in waste water. The treatment efficiency is very low when these methosare used to adsorption heavy metal ions low concentration in waste water. Recently,the biological adsorption method attracts many scientists,concern owing to its highefficiency and environmental-friendly.1) Used water-solubility cross-linker three（1-aziridine） trimethylolpropanetriacrylate（1）, three（1-aziridine） Ethoxylated trimethylolpropane triacrylate（2） andthree（1-aziridine） Pentaerythritol three acrylates （3） with chitosan. Casting to chitosanmembranes. It was characterized by FT-IR SEM, TG/DTG and elemental analysisrespectively. The Pb²⁺ions in wastewater and Cd²⁺ions as the research object, thethree（1-aziridine） Ethoxylated trimethylolpropane triacrylate（2） shows a higheradsorption capacity. Study the solution of the pH value, metal ion concentration,temperature, the dosage of the absorbent adsorption, ion strength of factors affectingthe performance of the adsorption and determined the best adsorption conditions. Theresults had indicated that the best conditions followed:286K, the dosage ofadsorbents for10mg, pH value is equal to5,7, the adsorbents to Pb²⁺, Cd²⁺ionsadsorption capacity was90mg g^-1,39mg g^-1respectively. The pseudo-first-order andsecond-order kinetic models were used to describe the kinetic data and the rateconstants were evaluated. The dynamical data fit well with the second-order kineticmodel, The Langmuir and Freundlich adsorption models were applied to describe theequilibrium isotherms at different particle sizes and isotherm constants were determined. The Langmuir model agrees very well with experimental data.2) chitosan（CTS） and poly（vinyl alcohol）（PVA） Were obtained by acasting/solvent evaporation method and crosslikned by aziridine(CTS/PVA^-1,CTS/PVA-2, CTS/PVA-3). The films were characterized by FT-IR, and TG. And thenthe influential factors of adsorption properties of CTS/PVA for the heavy-metal-ionsas Cu²⁺and Cd²⁺were studied. A systematic study was carried out to investigateinfluence of different conditions on the adsorption, such as pH value, initialconcentration，temperature, dosage of modified Chitosan, ionic strength etc. Itdetermined the optimal adsorption conditions: In normal conditions, the dosage ofadsorbents for10mg, pH value were7,6, CTS/PVA-3adsorbents to Cd²⁺ions, Cu²⁺maximum adsorption was46mg g^-1,46.5mg g^-1respectively. Adsorption dynamicsare in line with second-order kinetic models; The isothermal adsorption model fittingresults showed that the former Freundlich adsorption model to have higher linearfitting constant, the latter to Langmuir adsorption model have higher linear fittingconstant.3)11kinds of biosorbents were prepared using walnut shell from agricultureresidues by chemical modification and adsorption properties of Pb²⁺. By using batchadsorption techniques, the influence of pH, adsorbent dosage, concentration andtemperature on adsorption effect was investigated. In addition, the adsorptionthermodynamics and the adsorption kinetics were studied systematically.NaOH modified walnut which was used to investigate the adsorption behavior ofPb²⁺ions from aqueous solutions. The results had indicated that the temperature was283K, the adsorbent dose was10mg, the pH was5, adsorption balance after100minadsorption, the maximum adsorption capacity was133mg g^-1. The kinetic datasindicated that the adsorption fitted well with the pseudo-second-order kinetic model.The adsorption was well fitted by the Langmuir adsorption isotherm model. theadsorption processes for single molecule layer absorption.Epichlorohydrin modification of walnut powder absorbent, in289K, the Pb²⁺ions adsorption capacity was101.01mg g^-1. The kinetics study indicates that theadsorption is a pseudo-second-order process. The adsorption was well fitted by theLangmuir adsorption isotherm model. Langmui model can be a very good illustrate the adsorbent can effectively remove the water Pb²⁺ ions.