Study On Preparation And Adsorption Properties Of Hemicellose-based Heavy Metal Adsorbent

In this paper,hemicellulose was extracted and purified from pulping black liquor.Two kinds of hemicellulose-based heavy metal adsorbents were prepared,include hemicellulose/graphene hydrogel and a hemicellulose anionic adsorbent.The adsorption performance and mechanism of the heavy metal adsorbents were studied by different hemicellulose-based adsorbents.The results are as follows:1.The hemicellulose monosaccharides and uronic acid components were measured by ion chromatograph.The result showed that the content of xylose was the highest.The hemicellulose as the raw material,graphene as filler,acrylic acid as monomer,N,N-methylene bisacrylamide as crosslinking agent,hemicellulose/graphene hydrogel was prepared through the intercalation reaction.The optimum conditions for the preparation were:the amount of graphene,crosslinking agent and acrylic acid was 0.0410g,0.1500g and 7.2000g,respectively.FTIR showed that the hemicellulose,hemicellulose/graphene hydrogel appeared characteristic peaks,carboxyl groups were successfully introduced into hemicellulose/graphene hydrogel.The optimum conditions for the adsorption of Pb(II)were as follows:the initial concentration was 100-200mg/L,pH was 4.5,the adsorption time was 120min,and the temperature was about 35?.Langmuir,pseudo two order kinetics,Kannan-Sundaram intraparticle diffusion models,and the changes of FTIR,solution pH before and after adsorption indicated that the adsorption of Pb(II)by hemicellulose/graphene hydrogel was single molecular layer adsorption.Its intraparticle diffusion was divided into three control steps,and the adsorption mechanism may be mainly ion exchange and coordination,as well as physical adsorption.2.The hemicellulose anion adsorbent was prepared by hemicellulose as raw material,ring-opening etherification with epichlorohydrin,crosslinking amination with diethylenetriamine and quaternizing with triethylamine.FTIR showed that amino groups were successfully introduced into hemicellulose anionic adsorbent.The single component adsorption of heavy metal ions experiments showed that the optimum conditions for the adsorption of Cr(?),Cu(?)and Cd(?)by hemicellulose anionic adsorbent were as follows:the initial concentration was 400mg/L;the amount of adsorbent was 1.7g/L;pH were 2.5,5.5 and 5.5,respectively;and the time of rapid adsorption was 60min,100min and 100min,respectively.The multi-component competition of heavy metal ions and regenerated adsorption experiments showed that the hemicellulose anionic adsorbent had good selectivity to Cr(?),the adsorption performance was Cr(?)>Cu(?)>Cd(?)and it had ability to reuse,especially for adsorption of Cr(VI).Langmuir,Freundlich,Solid-liquid phase adsorption model,pseudo two order kinetics model,and the changes of FTIR,TG before and after adsorption indicated that The adsorption of Cr(?)by hemicellulose anionic adsorbent was single molecular layer adsorption,and the diffusion in the particles played a major role.The adsorption of Cu(?)and Cd(?)was a multi-molecular layer adsorption.Those adsorption processes were chemical adsorption-oriented,three control steps.And the graft amino groups were chelated with heavy metal ions.