Study On Preparations And Adsorption Performances Of Lignin Grafted β-Cyclodextrin

A new kind of water treatment named lignin graftedβ-cyclodextrin (L-β-CD) wassynthesized in alkaline solution from the wheat straw alkali lignin. The lignin based adsorbentnot only kept the original characterization ofβ-cyclodextrin to form inclusion complexes, butalso contained special structure that could coordinate to inorganic heavy metal ions. Itindicated that the new water treatment was high-effect, low cost and friendly to theenvironmen.The major contents of this research were composed of preparations of L-β-CD,adsorption performances of L-β-CD,preparations and adsorption performances of L-β-CDCa-alginate microspheres.There were two steps in the preparations of L-β-CD,the first,straw alkaline lignin wasepoxided by epichlorohydrin catalyzed by sodium hydroxide to prepare straw alkaline lignin-based epoxy resin. The structure of lignin-based epoxy was analyzed by FTIR and the contentof epoxy equivalent was measured by the method of hydrochloric acid- acetone. Influences ofreaction conditions such as the ratio of straw alkaline lignin and epichlorohydrin, the valume ofNaOH (16.7%, by weight), the time of reaction and the temperature were studied.Experimental results showed that the optimal conditions were 12 g epichlorohydrin per gram ofstraw alkaline lignin, the valume of NaOH (16.7%,by weight) 5 mL, the reaction temperature80℃, the reaction time 3 h, with the epoxy equivalent of 0.3623.The second,the multifunctional water treatment lignin graftedβ-cyclodextrin wasprepared from lignin-based epoxy resin in alkaline solution. The influences of the content ofβ-cyclodextrin, reaction temperature, reaction time and the volume of sodium hydroxide on theβ-cyclodextrin content were investigated. The results showed that the optimal syntheticalcondition was that the ration ofβ-cyclodextrin to lignin was 3 to 1 by weight, the reactiontemperation was 55℃, the reaction time was 3 hours and the volume of sodium hydroxide was25 ml(16.7% by weight) per gram of lignin, with theβ-cyclodextrin content of 30.88μmol/gunder this condition.The adsorption properties of lignin graftedβ-cyclodextrin for Cu²⁺,Pb²⁺,Cd²⁺ andorganic pollutants were studied in the model of polluted water. The results showed that thesaturated Q of Cu²⁺,Pb²⁺,Cd²⁺ reached 16.54mg/g,54.42mg/g,9.984mg/g respectively.The equilibrium time of Cu²⁺ was three hours. Equilibrium data of Cu²⁺ within temperaturerange of 20℃to 60℃and investigative concentration range fit well with Langmuir equation.Values of adsorption enthalpy, Gibbs adsorption energy, and adsorption entropy werecalculated according to the relationship of thermodynamic function and the adsorptionbehaviors were reasonably interpreted. The adsorption of Cu²⁺ on L-β-CD was an endothermic process of simultaneous chemical and physical adsorption. The saturated Q of phenol andphenylamine reached 2.325 mg/g and 5.382 mg/g respectively at 20℃, pH=7. Equilibriumdata of phenol and phenylamine fit well with Freundich equation. The equilibrium time ofphenol and phenylamine was three hours. When pH ranged from 3 to 11, the satuated Q ofphenol and phenylamine first increased and then decreased, with a peak value at pH=7.To improve the hydrodynamics of L-β-CD , L-β-CD Ca-alginate microspheres wereprepared by first mixing L-β-CD with sodium alginate, and then coagulation of sodium alginatein CaCl₂ solutions. The formability and swelling behavior of L-β-CD Ca-alginate microsphereswere studied. Comparing to L-β-CD, the adsorption properties of L-β-CD Ca-alginatemicrospheres were investigated. The L-β-CD Ca-alginate microspheres had good adsorptionproperties. The satuated Q of phenol was 2.367 mg/g at 20℃for 3 hours which equal to L-β-CD, while that ofphenylamin was 4.0515 mg/g for 3 hours which was lower than L-β-CD.The research was supported by grants from Scientific and Technological Key Program ofHeilongjiang Province (No.GB05B01).