STABILIREA PROPRIETĂŢILOR ACIDO-BAZICE ALE CĂRBUNILOR ACTIVI

Raisa NASTAS, Vasile RUSU, Tudor LUPAŞCU

Abstract


Au fost precizate unele aspecte metodologice ale tehnicilor de titrare vizuală (metoda Boehm) şi electrometrică (titrări alcalimetrice şi acidimetrice) pentru stabilirea proprietăţilor acido-bazice ale adsorbanţilor carbonici. Pe suprafaţa cărbunilor activi obţinuţi prin metoda fizico-chimică predomină grupările funcţionale bazice, pentru determinarea conţi­nutului lor fiind recomandată metoda titrării conductometrice acidimetrice. De rând cu grupările bazice, pe suprafaţa acestor cărbuni există şi grupări funcţionale acide, pentru determinarea lor fiind recomandată metoda titrării pH-metrice indirecte. Pe suprafaţa cărbunilor activi obţinuţi prin metoda chimică predomină grupările funcţionale acide, pentru de­ter­­minarea conţinutului lor fiind recomandă metoda titrării conductometrice alcalimetrice. Pentru determinarea grupări­lor bazice pe suprafaţa acestor cărbuni se recomandă metoda titrării pH-metrice indirecte.

EVALUATION OF ACTIVE CARBONS ACID-BASIC PROPERTIES

The methodological peculiarities of visual titration method (Boehm method) and electrometric (alkalimetric and acidimetric titrations) for researching of acid-basic properties of carbonaceous adsorbents have been specified. On the surface of active carbons obtained by physical-chemical method of activation the basic sites predominate being recom­mended acidimetric conductometric titration for their determination. Besides of such groups there are also acidic sites being recommended alkalimetric pH-metric back titration for their determination. On the surface of active carbons obtained by chemical activation the acidic groups predominate being recommended alkalimetric conductometric titration for their determination. Besides of such groups there are also basic sites being recommended acidimetric pH-metric back titration for their determination.


Keywords


active carbons, functional group, surface chemistry, electrochemical titration.

Full Text:

PDF

References


BENADI, H., BANDOSZ, T.J., JAGIELLO, J., SCHWARZ, J.A., ROUZAUD, J.N., LEGRAS, D., BEGUIN, F. Surface functionality and porosity of activated carbons obtained from chemical activation of wood. In: Carbon, 2000, vol.38, p.669-674.

BARTON, S.S., EVANS, M.J., HALLIOP, E., MACDONALD, J.A.F. Acidic and basic sites on the surface of porous carbon. In: Carbon, 1997, vol.35, p.1361-1366.

CONTESCU, A., CONTESCU, C., PUTYERA, K., SCHWART, J.A. Surface acidity of carbons characterized by their continuous pK distribution and Boehm titration. In: Carbon, 1997, vol.35, p.83-94.

MORENO-CASTILLA, C., LOPEZ-RAMON, M.V., CARRASCO-MARIN, F. Changes in surface chemistry of activated carbons by wet oxidation. In: Carbon, 2000, vol.38, p.1995-2001.

BOEHM, H.P. Some aspects of the surface-chemistry of carbon-blacks and other carbons. In: Carbon, 1994, vol.32, p.759-769.

BOEHM, H.P, DIEL, E., HECK, W., SAPPOK, R. Surface oxides of carbon. In: Angewante Chemie International Edition, 1964, vol.3, p.669-677.

BOEHM, H.P. Chemical Indentification of Superficial Groups. In: Advances in Catalysis, New York: Academic Press, 1966, p.179-274.

BOEHM, H. Surface chemical characterization of carbons from adsorption studies. In: Adsorption by carbons. BOTTANI EDUARDO, J., TASCO´N JUAN, M.D. (eds). Amsterdam: Elsevier, 2008. p.301-27.

SEREDYCH, M., HULICOVA-JURCAKOVA, D., LU, G.Q., BANDOSZ, T.J. Surface functional groups of carbons and the effects of their chemical character, density and accessibility to ions on electrochemical performance. In: Carbon, 2008, vol.46, p.1475-88.

SALAME, I.I., BANDOSZ, T.J. Surface chemistry of activated carbons: combining the results of temperature-programmed desorption, Boehm, and potentiometric titrations. In: Journal of Colloid and Interface Science, 2001, vol.240, p.252-8.

MENENDEZ, J.A., XIA, B., PHILLIPS, J., RADOVIC, L.R. On the modification and characterization of chemical surface properties of active carbon: Microcalorimetric, electrochemical, and thermal desorption probes. In: Langmuir, 1997, vol.13, p.3414-3421.

NASTAS, R., RUSU, V., GIURGINCA, M., MEGHEA, A., LUPAŞCU, T. Modificarea structurii chimice a suprafeţei cărbunilor activi vegetali. În: Revista de Chimie (Bucureşti), 2008, vol.59, p.159-164.

LUPASCU, T., PETUKHOVA, G.A., NASTAS, R., POLYAKOV, N.S. Pore structure and adsorption properties of stone active carbons prepared by physicochemical and chemical activation methods. In: Rus. Chem. Bull., 2006, vol.55, p.770-775.

GOERTZEN, S.L., THERIAULT, K.D., OICKLE, A.M., TARASUK, A.C., ANDREAS. H.A. Standardization of the Boehm titration: Part I. CO2 expulsion and endpoint determination. In: Carbon, 2010, vol.48, p.1252-1261.

MADERA, V., ALLEN, H.E., MINEAR, R.A. Non-metallic Constituents. In: Examination of Water for Pollution Control, A Reference Handbook, M. J. Sues, Wold Health Organization, Regional Office for Europe, Copenhagen, Denmark (Eds.), 1st Edition, Oxford-New York-Toronto-Sydney-Paris-Frankfurt: Pergamon Press, 1982. 310 p.

RUSU, V., NASTAS, R., GIURGINCA, M., MEGHEA, A., LUPASCU, T. Chimia suprafeţei adsorbanţilor carbonici. În: Materialele Simpozionului internaţional „Mediul şi Industria”, Bucureşti, 2007, p.140-145.

ADAMSON, A.W. Physical chemistry of surfaces. Third edition. New York: John Wiley and Sons, Inc., 1976. 700 p.

RUSU, V., LUPAŞCU, T. Chimia sedimentelor sistemelor acvatice. Proprietăţi de suprafaţă. Modele fizico-chimice. Chişinău: Elena VI, 2004. 272 p.

STUMM, W., MORGAN, J.J. Aquatic chemistry. Chemical equilibria and rates in natural waters. Third edition. New York: John Wiley and Sons, Inc., 1996. 1024 p.

OICKLE, A.M., GOERTZEN, S.L., HOPPER, K.R., ABDALLA, Y.O., ANDREAS. H.A. Standardization of the Boehm titration: Part II. Method of agitation, effect of filtering and dilute titrant. In: Carbon, 2010, vol.48, p.3313-3322.


Refbacks

  • There are currently no refbacks.