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Determination of Specific Surface—Solution Adsorption

比表面测定. —— 溶液吸附法. Determination of Specific Surface—Solution Adsorption. Contents. Purposes and Demands Principle Apparatus and Reagent Procedure Data Records and Processing Questions Attentions. ·. Purposes and Demands.

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Determination of Specific Surface—Solution Adsorption

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  1. 比表面测定 ——溶液吸附法 Determination of Specific Surface—Solution Adsorption

  2. Contents • Purposes and Demands • Principle • Apparatus and Reagent • Procedure • Data Records and Processing • Questions • Attentions

  3. · Purposes and Demands 1.Understand the principle of solution adsorption method. 2. Learn how to determine specific surface of micro-silica gel by adsorption method with methylthionine chloride solution.

  4. Principle • Specific-surface that stands for general surface of 1 g solid is an important characteristic parameter of porosity powder substance. It did good job in fields of manufacture such as catalyze, chromatogram, environmental protection and spinning and scientific research.

  5. We shall be concerned here with the method of methylthionine-chloride solution adsorption by which determine specific surface of micro-silica gel.

  6. Since tendency of methylthionine chloride to be adsorbed by most solid is the largest in dyestuffs had been found. It presents monolayer adsorption which is coincident with Langmuir adsorption isotherm.

  7. As stated in monolayer adsorption theory, when admolecules cover full on the surface of adsorbent, the area of 1g adsorbent seized by admolecule is the product that admolecule’s number multiply by the area of an adsorbed molecule.

  8. The total area of the solid is Where S, A, M , NA, W, ΔW, are respectively, specific surface with( cm2/g), the cross-sectional area of methylthionine-chloride molecule( 81.3×10-16cm2),

  9. molar mass of methylthionine-chloride( 373.9), Avogadro constant, the mass of silica gel（g） and the mass of methylthionine-chloride when silica gel has saturated adsorption.

  10. It is important to select a substance what has quite large specific surface in the experiment. • Methylthionine-chloride has two adsorption peaks in visible light region that are waves of 445nm and 665nm.

  11. Determine absorbance change in solution by 722 type of spectrophotometer on the foundation of the equation below

  12. 实验原理 Where C0 is the primary concentration of the solution, C is the concentration of saturated solution after adsorption and V is the volume of solution.

  13. Apparatus and Reagent • 722-spectrophotometer 1 • Conessi-oscillator 1 • Volumetric flask(100ml) 8 • Iodine measuring flask(100ml) 1 • Spheric aspirator 1 • Pipette(10ml, 25ml, 50ml) 3 • Methylthionine-chloride solution（500×10-3mg/ml） • micro-silica gel

  14. Procedure • 1.Determination of specific surface ⑴ Prepare Methylthionine-chloride solution of 50×10-3mg/ml for reservoir liquor. Pipette 10ml liquid of 50×10-3mg/ml to a 100ml volumetric flask and make up this solution.

  15. ⑵ Pipette 50ml this solution to a iodine measuring flask and add 50mg of silica gel，then surge it for half an hour. Pipette 25ml of this solution and make up other solution in a 100ml volumetric flask then determine the absorbance and look up the concentration C′ from the standard curve.

  16. Protract of standard curve. • Pipette reservoir solution of respectively 1, 2, 3, 4, 5 and 6ml to six 100ml of volumetric flasks and make up the terms of concentration of standard solution. Determine absorbance of those solution at biggest absorption wavelength of 445nm or 665nm.

  17. Methylthionine-chloride （500×10-3mg/ml） 1.00 2.00 3.00 4.00 5.00 6.00 Concentration （（×10-3mg/ml） 5 10 15 20 25 30 Absorbance 实验步骤

  18. Data Records and Data Processing • Look up C′ from standard curve base on the absorbance determined in step 1 and 2. • Figure out values of C according to the relation of C′ and C

  19. C＝（100/25）C′ C′ = mg/ml C = mg/ml C0 = mg/ml ΔW＝（C0－C）×V×10-3＝g

  20. Calculate specific surface of silica gel. NA：6.02×1023 A： cm2 M：373.9 W： g

  21. Questions • 1.Why should the adsorbed solution diluted before determination? • What’s the condition of Eq. 1 for practice?

  22. Attentions • Solution should be confected accurately.

  23. Outline for controlling 722-Spectrophotometer. • 1.Regulate the sensibility at the lowest value that is of the smallest amplificatory times. • 2.Electrify and warm-up for 20 min, set the switch at ‘T’.

  24. 3.Open the sample compartment, click“0%T”to make the value showed 0.000. • 4. Adjust the wave at appointed value. 5. Cover the door, adjust “100%T” to the value of 1.000, if not, improve its sensibility.

  25. 6.Determination of absorbance. Set the switch at “A”, according to the steps above and measure the value of absorbance. 7. Finally, clean the instruments, cut down the electricity and cover the dustproof.

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