| Chitosan is the only basic polysaccharide in nature, plenty of amino andhydroxyl groups on which molecular chain show good adsorption effect on metal ions,dye and organic matter. Montmorillonite is abundant in nature, which has goodcation exchange capability and large surface area. In recent years, chitosan/mo-ntmorillonite intercalation composites have attracted wide interest because of itsunique structure and functional properties. In this study, chitosan/montmorilloniteintercalation composites (CTS/MMT) have been prepared by polymer solutionintercalation. Salicylaldehyde modified chitosan/montmorillonite intercalationcomposites (S-CTS/MMT) and salicylaldehyde modified chitosan/cetyl trimethylammonium bromide modified montmorillonite intercalation composites(S-CTS/CTAB-MMT) were prepared, respectively, and the chemical structure wascharacterized. Adsorption properties for reactive dyes and phenols with S-CTS/MMTand S-CTS/CTAB-MMT as adsorbent have been investigated. The effect ofexperimental conditions on the adsorption efficiency, adsorption thermodynamics andkinetics were investigated in detail. The regeneration performance of the adsorbentwas also studied.The main contents and conclusions are summarized as below:(1) The CTS/MMT have been prepared by polymer solution intercalation, andthen characterized with Fourier transform infrared (FTIR) and X-ray diffraction(X-RD). The effects of molar ratio of CTS to MMT, temperature, initial pH andconcentration of the dye solution, mass of adsorbent on adsorption capacities forReactive Red dye (RR136) have been investigated in detail. The results indicated thatthe optimum adsorption condition was using CTS/MMT composite with CTS toMMT molar ratio of5:1as adsorbent, adsorption temperature20oC and pH value ofRR136solution3. It was shown that all the adsorption processes were better fitted by the Langmuir equation, and the thermodynamic parameters indicated that theadsorption process of RR136onto CTS/MMT was spontaneous, exothermic anddominated by physical adsorption. All the adsorption processes were better fitted bythe pseudo-second-order equation, indicating that the rate of adsorption is determinedmainly by external particle diffusion process. For15times consecutiveadsorption/regeneration, adsorption capacity and regeneration efficiency was266.27mg/g and60.5%, respectively, which indicated that the intercalation compoundadsorbent has better regeneration reuse potential.(2) The salicylaldehyde modified chitosan (S-CTS) was prepared by molecularmodification for chitosan with salicylicaldehyde, and then intercalatedmontmorillonite to get S-CTS/MMT. Adsorption properties for phenol,4-chlorinephenol,4-nitro phenol and hydroquinone with S-CTS/MMT as adsorbent have beeninvestigated in detail. The results showed that the adsorption capacity of S-CTS/MMTfor phenols were in order of4-nitro phenol,4-chlorine phenol, hydroquinone andphenol. Adsorption processes were better fitted by the Langmuir equation, whichindicated that adsorption sites on surface of adsorbent belonged to the same type, andadsorption behavior closed to the theory of monolayer adsorption. All the adsorptionprocesses were better fitted by the pseudo-second-order equation, indicating that therate of adsorption is determined mainly by external particle diffusion process. Theadsorption of phenols onto S-CTS/MMT were predominated by π-π interaction,hydrogen bonding and hydrophobic interaction, not electrostatic interaction.(3) The cetyl trimethyl ammonium bromide modified montmorillonite(CTAB-MMT) was prepared by chemically modified of montmorillonite, and thenCTAB-MMT intercalated with S-CTS, S-CTS/CTAB-MMT were obtained. S-CTS/CTAB-MMT have been used for adsorption of phenol,4-chlorine phenol,4-nitrophenol and hydroquinone. The results indicated, compared with S-CTS/MMT,adsorption performance of S-CTS/CTAB-MMT improved significantly. Adsorptionproperties of phenols onto S-CTS/CTAB-MMT were better fitted by the Freundlichadsorption model, which indicated that the adsorption process was multilayeradsorption through intermolecular interactions. The kinetics results showed that the adsorption processes were better fitted by the pseudo-second-order equation,indicating that the rate of adsorption is determined mainly by external particlediffusion process. The adsorption interaction of phenols and S-CTS/CTAB-MMTincluding π-π interaction, hydrogen bonding and hydrophobic interaction of S-CTSand phenols molecules, and electrostatic interaction between cationic surfactants ofCTAB-MMT and phenols. Regenerative adsorption results indicated that for5timesconsecutive adsorption/regeneration, regeneration efficiencies of4-chlorine phenoland4-nitro phenol were54.9%and44.2%, respectively, and the adsorbent stillmaintain layer structure. |
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