Gupta, P. N.

Khan, I. A.

Malik, Wahid U.

English

NOPR

Indian Journal of Chemistryver, 14A, Jnly 1976, pp. 466-468Surface Area of Hydrous Oxides by Dye Adsorption MethodWAHID U. MALIK, P. N. GUPTA* & I. A. KHANtChemistry Department, University of Roorkee, RoorkeeReceived 27 February 1975; accepted 22 September 1975The adsorption behaviour of alizarin sulphonic acid, malachite green, methyl orange andmethylene blue 011 hydrous oxide gels such as silicic acid, alumina and ferric oxide has beenInvesttgated. The surface areas of these gels have also been evaluated (1) from the monolayercapacity of the adsorbents, and (2) from the heat of immersion method. The results obtainedby the two methods are comparable.THE interaction of dyes with metal hydrousoxide sols and gels has been studied by anumber of workers':". However, the effectof factors like shape and size of the dyestuff mole-cules, orientation on the surface of the adsorbent,pH, micellar structure of the dye, nature of theasdorbent, etc., has not been studied in depth. Withthis aim we have carried out investigations on theadsorption of dyes on a number of hydrous oxidegels. In order to assess the role of these factors inthe adsorption phenomenon and also to determinethe surface area of hydrous oxide gels, the adsorptionof dyes such as alizarin sulphonic acid, malachitegreen, methyl orange and methylene blue on thesegels has been studied and the results are presentedin this paper.Materials and MethodsSodium salt of alizarin sulphonic acid, methylorange, methylene blue and malachite green used inthe investigations were of analar grades. The gelswere prepared by the dialysis of the sols of silicic acid,alumina and ferric oxide prepared by the methodsrecommended by Hatschek", Weiser" and Krecke"respectively. Silicic acid gel was dried in an openfurnace at 2100 for 24 hr and the remaining two at1800 for 24 hr. The gels were passed through BS100 sieve, and presoaked in Britton-Robinson bufferof pH 2·0 after drying.Bausch & Lomb Spectronic-lOO spectrophotometerwas employed for the spectral measurements. Theheats of immersion were measured by the methodof Zettelmoyer et al.IO• A small rise in temperaturewas registered with the help of a thermistor inconjunction w.th a suitable resistance bridge. Thereproducibility of the heat of immersion valuesvaried between ± 3 and 4%, depending upon the typeof the gel used.Procedure - The samples for adsorption measure-ments were prepared in the following manner: 100mg of silicic acid gel + (i) varying amounts (0,6,*Present address: Department of Chemistry, KashmirUniversity, Srinagar.tPresen t address: Department of Chemistry, TahrazUniversity, Tahraz (Iran).4660'7,0·8,0'9 and 1·0 ml of 1·5x10-4M) of alizarinsulphonic acid; (ii) (1'0, 2·0, 3·0, 4·0 and 5·0 ml of1·96x 10-5M) of malachite green; (iii) (1·0, 2,0, 3·0,4·0 and 5·0 ml of 4·51 X 10-6M) of methyl orange;(iv) (1·0,2·0,3·0, 4·0 and 5·0 ml of 3·41 X 10-5M) ofmethylene blue.The total volume was made up to 10m1 by addingthe requisite amount of B.R. buffer (5·0 ml) andwater.Similar sets were prepared by taking 100 mg eachof ferric oxide and alumina gel.The samples were agitated thoroughly for equili-bration. After 24 hr, [dye] in equilibrium withadsorbent was measured spectrophotometrically andthe amount of dye adsorbed was found from thedifference in the optical density values. The ad-sorption isotherms were constructed from theamounts of dye adsorbed in the samples.Results and DiscussionIt is well known that a molecule having a highdegree of polarizability in three directions can exhibitthree bands, and in general, the wavelengths at thepeaks are referred to as first, second and third bandsin order of decreasing wavelengths. These dyesare characterized by oscillations in more than onedirection. The surface areas corresponding to majororientation for the dyes sodium alizarin sulphonate,malachite green, methyl orange and methylene blueare 28·2, 49·0, 39·5 and 28·6 A2 respectively.Any deviation from Beer's law is attributable toaggregation, and the degree of association betweenthe dye molecules can be obtained by this assump-tion-'. The concentration range selected in thepresent study was such that the dyes obeyed Beer'slaw and remained monomer in the concentrationrange under study.Nature of isotherms - Giles et al.12 have shown thatthe adsorption on inorganic oxides is either end-onas with polar molecules or flat-on as with dye stuffs,etc. These authors have shown that for a particulartype of adsorption there is a need to determinespecific effective cross-sectional area of the adsorbedmolecules from which one can obtain different orien-tations of the adsorbed molecules from the shapeMALIK et al .: SURFACE AREA OF HYDROUS OXIDESFig. 1 - Plots of equilibrium concen.tratior.s of the dyes versus x/m [(1) Silica gel + alizarin sulphonic acid. (2) silicagol + methyl orange. (3) silica gel + malachite green. (4) silica gel + methylene blue. (5) ferric oxide gel + alizarinsulphonic acid. (6) ferric oxide gol + methyl ora; .ge. (7) ferric oxide gel + malachite green, (8) ferric oxide gel + methyleneblue, (9) alumina gel + alizarin sulphor.icacid. (10) alumina gel + methyl orar.ge, (11) alumina gel + malachite green,and (12)alumina gel + methylene blue)of the isotherm. In our case it was found that theadsorption of alizarin sulphonic acid on ferric oxideand alumina was flat-on (Fig. 1. curves 5 and 9)giving a normal shape isotherm (L2) (the terminologyused here and thereafter is the same as recommendedby Elworthy-s). Similarly methylene blue gaveL2 type isotherm (Fig. 1, curve 4) with silica geland Ll type isotherm (Fig. 1, curve 8) with ferricoxide as per BET classification. The silica gel-alizarin sulphonic acid and ferric oxide-methyl orangesystems result in a well established Cl constantpartition like Henry's law range in adsorption ofvapours, while alumina-methylene blue gave asecond plateau (Fig. 1, curve 12) about twice theheight of the first which is typical of L4 type isotherm.The second plateau probably represented a re-orien-tation of the adsorbed molecule to give end-on ad-sorption with increased concentration, thereafter.further layers may build UP. as is shown by afurther steep rise in the isotherm. The end-onadsorption from water gives the S2 isotherm whichis intially convex to the concentration axis similarto that obtained in the case of adsorption ofmalachite green on both silica and alumina. Theend-on adsorption from solvent gives another iso-therm which is initially concave to the concentrationaxis and with a plateau resulting in a Langmuir typeLmx isotherm obtained for silica-methyl orange andferric oxide-malachite green systems. The Lmxtype of adsorption which is more precisely knownTABLE 1- COMPARISON OF SURFACE AREA (5) OBTAINEDBY ADSORPTION DATA AND HEAT OF IMMERSION METHODAdsorbent= 6Hs x 10'(ergsjg]5 (ml/g) fromAdsorptiondataHeat ofimmersionALIZARIN SULPHONIC ACID(A) 1394 214 210(B) 1018 281 267(C) 936 243 252MALACHITE GREEN(A) 1376 211 203(B) 958 265 264(C) 900 234 230METHYL ORANGE(A) 1374 209 202(B) 930 252 262(C) 880 228 226METHYLENE BLUE(A) 1346 207 200(13) 1000 276 261(C) 825 213 210*(A) = silicic acid gel-water, hi = 650 ergs em-ll.(B) = ferric oxide gel-water, hi = 362 ergs cm-t.(C) = alumina gel-water. hi = 385 ergs em-s.467INDIAN J. CHEM., VOL. 14A, JULY 1976as negative adsorption, may be attributed to theincreasing concentration of the solute whereby thesolvent is adsorbed more and more. Based onthe data of Ostwald and Izaguirre= a successfultheory regarding this complex adsorption behaviourhas been developed by Bartell and Sloan-e. Ourdata fit well with this theory.Surface area - The method-" based on assumptionthat the adsorption was confined to a monolayerwas used to calculate the surface area using Eq. (1).55 + 55 - 5 - XmonoNXA (1)HI 1 n. 2 - - M '"where n~ and n~ are the number of moles of eachcomponents adsorbed, 51 and 52 are the areaoccupied by 1 mole each of the components. Xmonois the monolayer capacity in grams of solute pergram of solid, Nand M are Avogadro's number andmolecular weight respectively, A is the area occupiedby one molecule of solute in a closely packed filmon the surface of the solid, and 5 is the surface area.The values calculated by us are given in Table 1.The results have been verified from the heat ofimmersion measurement employing the relationship!l.Hi = hiS ... (2)where !l.H' is the heat of immersion (in ergs) per gramof solid, and hi is the standard heat of immersionper unit area of the solid in the given liquid.The hi values for the system silica acid gel-water",ferric oxide-water-s and alumina oxide gel-water-"have been reported to be 650, 362, 385 ergs crrr"respectively. It may be noted that the values of 5468calculated by both the techniques compare favourably(Table 1). The maximum and minimum valuesobtained for alizarin sulphonic acid were 281 and210 m2 g-l respectively which are not unexpected.References1. MARKER, H. & GORDON, M., Ind. Engng Chem., 16(I924), 1188.2. WHITE, J. F. & GORDON, M., J. phys. Chem., 31 (1927),1764.3. GILES, C. H., EASTON, U· A. & MEKAY, R. B., J. chem,Soc., (1964), 4495.4. GYANI, B. P., j. Indian chem. Soc., 28 (1951), 503.5. TEWARI, S. N., Kolloid Z., 128 (1952), 19.6. DUTTA, R., Bull. chem. Soc. japan, 37 (1964), 4.7. HATSCHEK, E., Laboratory ma.nual of elementary colloid(J & A Churchill Ltd, London), 1947, 50.8. WEISER, H. B., J. phys. Chem., 24 (1920), 525.9. l(1{ECKE, A, J. prakt. Chem., 2 (1871), 286.10. ZETTLEMOYER, A. C., YOUNG, G. J., CHESSICK, J. J. &HEALEY, F. H., J. phys. Chem., 57 (1953), 649.11. PUGH, D., GILES, C. H. & DuFF, D. G., Trans. Faradaysoc., 67 (1971), 563.12. GILES, C. H., MACEWAN, T. H. & NAKHAWA, S. N., 1·chem. soc., (1960), 3973.13. ELWORTHY, P. H., Solubil ization (Academic Pres's,Loidon), 1969, 203.14. OSTWAI_D, WOo & IZAGUIRRE, R. DE., Koll. Z., 30 (1922),279; 32 (1923), 57.15. BARTELL, F. E. & SLOAN, C. rc., j. Am. chem, Soc., 51(1929), 1637, 1643.16. GILES, C. H. & NAKHAWA, S. N., j. appl. Chem., 12 (1962),266.17. MACKRIDES, A. C. & HACKER""AN, N., J. Phys. Chem.,64 (1960), 594.18. GOODMAN, J. F., Ph.D. t hesis, London University,LO<1do:'., 1955.19. WADE, W. H. & HACKERMAN, N., j. Phys. Chem., 64(1960), 1196.

Surface Area of Hydrous Oxides by Dye Adsorption Method

http://nopr.niscair.res.in/bitstream/123456789/53791/1/IJCA%2014A%287%29%20466-468.pdf

Surface Area of Hydrous Oxides by Dye Adsorption Method

Abstract

Similar works

Full text

Available Versions

NOPR