Studies On Crosslinked Carboxymethyl Modification Of Konjac Glucomannan And Its Absorption And Desorption Properties For Metal Ions

Konjac glucomannan(KGM),an abundant natural polysaccharide coming out after starch and celluloses,gradually became promising environment friendly material.This article make KGM as main object of research,basing on the solution behavior of KGM in different pH values,intends to study the optimization synthesis conditions and the capacity of adsorption and desorption for metal ions of Crosslinked Carboxymethyl Konjac Glucomannan,analyse the structural characteristic of KGM,CCMKGM and MCCMKGM via Fourier Transform Infrared Spectrum,Laser Raman Spectrum,X-Ray Diffraction and Scanning Electron Microscopy etal.The main results of this paper are as follows:1.Primary study on solution conformation of Konjac Glucomannan in different pH valuesThe instrinsic viscosity in different pH values of Konjac Glucomannan(KGM) solution was studied finely by viscosimetry.The effects of pH value and urea concentration on KGM conformation are discussed by KGM-Congo red complex.The instrinsic viscosity experiment showed that the instrinsic viscosity of 0.6g/L KGM solution is 1520.2mL/g,1472mL/g,1616.6mL/g,1590.5mL/g,1414.1mL/g in pH value 4,6,7,8 and 10,so the correlative Molecular Weight(Mw)is 1.07×10⁶,1.04×10⁶, 1.18×10⁶,1.16×10⁶,0.99×10⁶.The KGM-Congo red complex experiment suggested that KGM might have certain helical conformation,which is destroyed at high pH value.2.Study on preparation of Crosslinked Carboxymethyl Konjac GlucomannanUnder alkaline conditions,isopropyl alcohol as dispersing agent,epichlorohydrin (ECH) as crosslinking,Crosslinked Carboxymethyl Konjac Glucomannan(CCMKGM) was prepared through reaction of monochloroacetic acid(MCA) and konjac glucomannan.Conditions of preparation of modified KGM were studied and optimized by quadratic regress revolving cross-experiment.The optimization synthesis conditions analyzed by SAS soft were NaOH 12mL,MCA 12mL,ECH 1mL.Under this condition, the degree of substitution of CCMKGM is 0.6068.3.Study on the capacity of adsorption and desorption for metal ions of Crosslinked Carboxymethyl Konjac GlucomannanThe effect of metal ions concentration,contact time,pH,adsorbent amount and temperature on the adsorption of Cu²⁺,Cd²⁺,Cr³⁺ and Pb²⁺ in water onto CCMKGM are investigated in this paper.The Adsorption Kinetics of CCMKGM for metal ions are discussed.The results show that metal ions concentration,contact time,pH,adsorbent amount are the affecting factors on adsorption capacity.The optimization adsorption conditions are metal ions concentration 200mg/L,adsorbent amount 0.75%,pH value 5, temperature 25℃.The adsorption equilibrium of the four metal ions onto CCMKGM can carried out after 20 mins,then,the adsorption rates are Cu²⁺ 93.51%,Cd²⁺ 91.02%,Cr³⁺ 89.68%and Pb²⁺ 97.64%.The desorption for metal ions results show that the desorption capacity is Cd²⁺99.6%,Cu²⁺86.3%,Cr³⁺21.8%and pb²⁺5.8%.4.Study on the structural characteristic of KGM,CCMKGM and MCCMKGMStudy on the structural characteristic of KGM,CCMKGM and MCCMKGM via Fourier Transform Infrared Spectrum,Laser Raman Spectrum,X-Ray Diffraction and Scanning Electron Microscopy etal.Fourier Transform Infrared Spectrum and Laser Raman Spectrum suggested that An acetyl group exists in KGM structure,deacetylation occurs on CCMKGM after the reaction of Crosslinked Carboxymethyl.In addition,many structures have changed in fingerprint district.The X-ray diffraction pattern analysis revealed that the X-ray diffraction patterns of KGM mainly show amorphous structure and only a few crystal.CCMKGM crystal structure has no big change,but find some new diffraction peaks,the peak intensity of MCCMKGM decreased significantly and surface spacing became smaller.Scanning electron microscope suggested that KGM surface of the cell wall are very close and smooth.The surface of CCMKGM granule is bumpiness and grievances.It formed a thick absorption layer on the surface of MCCMKGM.