| Mesoporous molecular sieve MCM-41, which possesses readily pore size, verylarge specific surface area and regular pore structure, is a new type of inorganicporous material. Its uniform structure providing unexampled free space to largemolecular reactions and its characteristics that can match the pore size, theconcentration and the strength of acid sites with application requirements all indicatethat this kind of molecular sieve has a wide potential applications in areas of catalysis,immobilization of active enzyme, preparation of functional materials, sorption andseparations of matter.Surfactants C16H33(CH3)3NBr(1631) were used for syntheses of silic-abasedmesoporous molecular sieves MCM-41 by the hydrothermal crystallization. By meansof XRD, TEM, SEM and other modern techniques, the structure and properties ofmesoporous molecular sieve MCM-41 were studied. Results indicated that structureof MCM-41 molecular sieve has uniformly arranged channels.In this paper, the MCM-41 mesoporous molecular sieve was used to adsorbheavy-metal-contained waste water and mephitis. Optimal experimental conditions,stability, and requirements of regeneration in such sorption were studied. Based on theorthorhombic experiment, the optimal conditions was determined: 50min, pH=4.8,and 30°C for As(III);25min, pH=6.2 and 30°C for Hg2+;pH=4.8, and 30°C for As(III);25min, pH=6.2 and 30°C for Cr(VI).Through static experiments, the results showed that, at 25℃, the adsorption date ofCr(VI), Hg2+ and As(III) ion fits well into the Langmuir adsorption isotherm andFreundlich linear equation. MCM-41 was found to be highly effective for theadsorption of Cr(VI), Hg2+ and As(III) ions, exhibiting high metal ion uptakecapacities of 84.81, 34.01 and 13.95 mg·g-1,, respectively.At 25℃, the adsorption of SO2 and NO2 was fitted to Langmuir isotherms. TheLangmuir fitting equation of SO2 is that 1/Qe=2.29/Ce-0.95, r2=0.9319;The Langmuirfitting equation of NO2 is that 1/Qe=0.0092/Ce+4.3898, r2=0.9999.The adsorption kinetics of heavy-metal-ion by MCM-41 was studied through staticexperiments. The results show that the adsorption rate for As(III) and Cr(VI) appearsto be the first-order kinetics and the adsorption rate for Hg2+ appears to be thesecond-order kinetics. The kinetics equation was worked out, where for As(III) at 25℃,y1=-0.2208-0.0648x1 (r12=0.9895), at 40℃, y2=-0.0128-0.0729x2 (r22 = 0.9987) and at55℃, y3=-0.3264-0.0994x3 (r32=0.9679);for Cr(VI) at 25℃, y1=-0.0291 -0.2121x1(r2=0.9911), at 40℃, y2=-0.2295-0.2167x2 (r2=0.9786), and at 55℃, y3=-0.1433 -0.2287x3(r2=0.9918);for Hg2+ at 25℃, y=0.2916-0.0010x, r2=0.9847.The thermodynamics research on the sorption of heavy-metal-ion by MCM-41demonstrated that the ?H is greater than zero which indicated that adsorption processis an endothermic reaction, and the value of △G As(Ⅲ), △G Hg(Ⅱ) and △G Cr( Ⅵ ) is-8.289 KJ·mol-1, -2.700 KJ·mol-1, and -5.474 KJ·mol-1 , respectively, which indicatedthat adsorption process is spontaneous process. The process of heavy-metal-ionadsorption on MCM-41 is physic and chemic effect coexisting.The results of competition adsorption experiment show that the order of adsorptioncapacity of MCM-41 to heavy-metal-ion is Cr(VI) > Hg2+> As(III). The reason ofdifference of adsorption capacity is that the greater ion radius in effect has the moresteric hindrance.In addition, we apply D-R theory to deal with experiment date, and the result showthat saturation adsorption quantity worked out by D-R equation is fit well intocorrespondence of date that get from Langmuir fitting. So D-R theory has meaning todirect adsorption experiment.
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