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Study on Preparation and adsorption of heavy metal ions on MCM-41 mesoporous molecular sieve

Author: ZhuWenJie
Tutor: MaWenHui
School: Kunming University of Science and Technology
Course: Physical Chemistry of Metallurgy
Keywords: the MCM-41mesoporous molecular sieve rice hull ash silicafume adsorption of heavy metal ionic
CLC: TQ424.25
Type: PhD thesis
Year: 2013
Downloads: 31
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Abstract


Due to their excellent performances such as large specific surface area, uniform pore size distribution and rich surface functional groups, the M41s mesoporous molecular sieves have attracted great interest of scientists, since they had successfully synthesized by Mobil researchers in1992. On account of the properties of silica source, template system, synthesis methods etc, the MCM-41mesoporous molecular sieve has not been widely utilized so far.In this work, industrial solid waste, rice husk ash and silica fume were chosen to be silica resources instead of traditional organic silica resource. The main purpose of this work is to synthesis the MCM-41mesoporous molecular sieve with special morphology from particular macroscopic morphology of silica sources, studying the synthesis mechanism in condition of impurities, moreover characterizing the structure of mesoporous molecular sieve and the absorptive property of heavy metal ionic. This dissertation mainly was consisted by the following several aspects.1. Pretreatment and acid leaching purification of silica fumesBased on the characterization upon the structure and properties of silica fume, the purification process of silica fume had been determined. Firstly silica fume had been pretreated and then was leached by acids using two-steps method. The influence of concentration of acids, reaction temperature, reaction time, have been discussed. The mechanisms of cleaning impurities have also been studied. The best purification experiment conditions were as fellows:concentration of H2SO4and HC1was6mol/L, liquid-solid ratio was50:1, reaction temperature was60℃, reaction time was2h, and stirring speed was600r/min.2. MCM-41mesoporous molecular sieve synthesized from silica fumesMCM-41mesoporous molecular sieve were synthesized by hydrothermal method using acid leached silica fumes as silica source.The factors to influence the structure and performances of MCM-41were studied, such as properties of silica source, CTAB/SiO2molar ratio, NaOH/SiO2molar ratio, crystallization time, crystallization temperature, the type of template and the post-treatment technology. The mechanisms of synthesizing this MCM-41material were also discussed. The proper parameters under this trial condition were selected:CTAB/SiO2molar ratio was0.15, NaOH/SiO2molar ratio was0.2-0.3, Crystallization time was48h; Crystallization temperature was90℃; Template system was the mixture of CTAB and PEG6000.The MCM-41has been used for the adsorption of Cu(Ⅱ), Pb(Ⅱ) and Cd(Ⅱ) from aqueous solutions. The influence of the dosage of mesoporous molecular sieve, pH value of solution, adsorption time and initial concentration of heavy metal ions has been discussed. The adsorption isotherm, adsorption kinetics and the adsorption mechanism of heavy metal ionic of MCM-41have also been analyzed.3. MCM-41mesoporous molecular sieve synthesized from rice husk ashBased on the characterization upon the structure and properties of rice hull ash, the pretreatment technologies have been determined. MCM-41mesoporous molecular sieve was synthesized by hydrothermal method with rice husk ash as silica source. The factors such as CTAB/SiO2molar ratio, NaOH/SiO2molar ratio, crystallization temperature and time crystallizing were studied. The mechanism of synthesizing this MCM-41material was also discussed. The optimal parameters of synthesis for this silica source were listed in following:pH value was12, CTAB/SiO2molar ratio was0.05, and Crystallization time was72h.4. The study of MCM-41organic functionalization and heavy metal ionic adsorption performanceOrganic ligands containing fuctional groups (-NH2and-SH) were grafed to the surface and inner pore of a mesoporous molecular sieve MCM-41prepared from silica fume as silica source. The organic-inorganic composites were used for the adsorption of Cu(Ⅱ), Pb(Ⅱ) and Cd(Ⅱ) from aqueous solutions. The adsorption isotherm, adsorption kinetics and thermodynamics are exmined. The adsorption mechanisms of heavy metal ionic were also analyzed after the functionalization of MCM-41.

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CLC: > Industrial Technology > Chemical Industry > Reagents and the production of pure chemicals > Adsorbent > Inorganic adsorbent > Used as artificial silicate adsorbent
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