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Adsorption of Polyvinyl Alcohol from Aqueous Solution on Montmorillonite Clay Substrate.

S. K. Guha
Department of Chemistry, Dhaka University, Dhaka, Bangladesh.

S. M. Imamul Huq
Department of Soil Science, Dhaka University, Dhaka, Bangladesh.

T. S. A. Islam
Department of Soil Science, Dhaka University, Dhaka, Bangladesh.

M. Y. A. Mollah
Department of Chemistry, Dhaka University, Dhaka, Bangladesh.

H . Ahmed
Department of Chemistry, Dhaka University, Dhaka, Bangladesh.

Abstract/ Executive Summary:

The adsorption of polyvinyl alcohol from aqueous solution on high Mirf; cc area substratc-montmorillonite clay was examined . At low polymer concentration the system obey a high affinity type adsorption ISO therm. Above a certain coveralls the adsorption of polymer was found to be Langmuirian. Amount of polymer ad obscurer gram of clay w:" found to be more then 7 time> than the annual required for complete coverage of the surface. Adsorption w01 found he increased with increase in the temperature and dependent on solution like P11 and ionic strength.

Keywords: Soil, Caly, Alcohol, Montmorillonite, Clay substrate.

Location: Department of Chemistry, Dhaka University

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Contamination of soil

Objectives:

To identify adsorption isotherms for montmorillonite clay substrate under a wide range of solution conditions.

Methodology:

Montmorillonite clay (Panther Creek. Miss. U.S .A.) was purchased from Ward's National Science Establishment. The clay was grounded and sieved. Surface area of the dry clay was obtained by nitrogen adsorption and elemental analysis by name ionization. The clay was identified using the JCPDS powder diffraction files. Electron micrograph of the clay. Polyvinyl alcohol was supplied by the manufacturer (E. Merck). Molecular weight of the polymer is 72,000 g/mole. All the other reagents were of analytical grade. Both the polymer and the clay were used without further purification. Aqueous polymer solution was prepared by adding required amount of polymer to 300 ml of distilled water under vigorous agitation for ca 30 sec. The polymer dispersed slurry was immediately added to 700 ml of water and stirred vigorously until dissolution. The PYA concentration in the supernatant (after the adsorption by clay) was determined calorimetrically by measuring the colour intensity of the complex of PYA with iodine in the presence of boric acid and PYA. Calibration curves were drawn by plotting adsorptiance of PYA-iodine complex against PYA concentration. To 6 m l of PV A solution ( 10-60 ppm) were added 4 ml of the reagent. The colour intensity of containing 0.64 M H3 3 2 the complex was measured using a Pye Unicam SP6 series spectrophotometer wit h 10 mm cell at 670 nm. To a 100 ml of polymer solutions having concentrations ranging between 30 to 200 ppm, 0.20 g. of clay was added and mixed carefully by shaking for half an hour.

Source of Information: Bangladesh J. Agri. Re. 12(): 17-31 (Dhaka University Institutional Repository)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Above a certain coverage (40 mg of polymer/g clay). adsorption of PYA was found to be Langmuirian. The fit to the Langmuirian equation up to a certain extent is quite good. However, it should be mentioned that PYA adsorption does not satisfy the conditions required for Langmuir type of adsorptions. It has already been pointed out that PV A adsorption is irreversible. and exact equilibrium between the adsorbate and the bulk solution is not attained with in the time intervals indicated. However, assuming the model, some useful information could be obtained. The slope of the Langmuir plot is a measure of polymer required for complete coverage of the substrate surface which was found to be 220 mglg of clay . The surface area of each segment of PYA determined by Lank veld ( 1970) from the compressibility of PYA in the water paraffin interface was 25A02 in a closed packed monolayer . Assuming the same value on clay, the amount of PYA required for complete coverage would be 0.48 mg per m2 of the surface. Surface area of montmorillonite clay is 63.2 m2/g. From this, it follows that 31 mg of polymer is necessary for complete coverage which is about 7 times less than the actual amount adsorbed and which is equivalent to seven monolayers. Thus at maximum adsorption, one seventh of the total number of segments, at most, is adsorbed on the surf ace and the polymer layer must be very thick. At low coverage a high proportion of segments can be adsorbed giving a thinner layer. The empirical formula of the clay (A1. Mole ) Si 0 uCOH) JCA obtained 3 2 0 7 118 8 2 1 1 from the elemental analysis suggests some substitution of Nontronite and Beidellite to the ideal montmorillonit ecomposition .

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