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Adsorpcja acetonu na materiałach ilastych

100%

Pliś I. , Warzybok M. , Prokop W. , Petrus R. , Warchoł J.

tom T. 18, nr 2

233--243

Celem niniejszej pracy było porownanie adsorpcji par acetonu na węglu aktywnym i naturalnych adsorbentach opartych na bentonicie. Naturalny bentonit poddano chemicznej modyfikacji poprzez dealuminację kwasem HCl, wymianę jonową solami: chlorkiem cezu (CsCl) i bromkiem tetrametyloamoniowym (TMA-Br) oraz interkalację. Otrzymane adsorbenty zastosowano do adsorpcji par acetonu. Badania przeprowadzono w warunkach kolumnowych w specjalnie do tego celu zbudowanej instalacji laboratoryjnej, składającej się z butli zawierającej mieszaninę par acetonu w azocie o danym stężeniu, kolumny wypełnionej badanym adsorbentem, przepływomierza oraz analizatora stężeń. Pomiar stężenia acetonu na wylocie z kolumny wykonano (on-line) techniką chromatografii gazowej. Badania przeprowadzono w temperaturze otoczenia pod ciśnieniem atmosferycznym dla wejściowego stężenia acetonu równego 200 ppm. Na materiale modyfikowanym TMA-Br wyznaczono izotermę adsorpcji, którą wykorzystano do modelowania równowagi adsorpcji. Zastosowano równania empiryczne dwu-, troj- i czteroparametrowe.

The aim of the present work was to compare adsorption of acetone vapors on activated carbon and natural adsorbents based on bentonite. Natural bentonite was chemically modified by acidic dealumination using HCl, by cationic exchange with cesium chloride (CsCl) and tetramethylammonium bromide (TMA-Br) salts and by intercalation. There were determined basic physical and chemical properties of the adsorbents and the investigation for acetone adsorption capacity was carried out. For comparative purposes, also active carbon (AC) was tested. The research was realized in a self-made system consisting of a bottle with acetone-nitrogen mixture with given concentration, fixed-bed column with tested adsorbent, flowmeter and concentration analyzer. Concentrations on column inlet and outlet were monitored on-line using gas chromatography technique. The tests were implemented on 0.5 g samples of active carbon, natural bentonite (B) and four modified bentonites: one treated with hydrochloric acid (B-HCl), two modified with Cs+ and TMA+ cations (B-Cs, B-TMA) and one intercalated. Samples were previously dried at 150°C for one hour. The tests were performed for atmospheric pressure, ambient temperature and inlet acetone concentration of 200 ppm. The amounts adsorbed by examined materials were calculated with integral method on the basis of obtained breakthrough curve. Non-modified bentonite (B) had much lower acetone adsorption capacity than modified ones. The determined acetone adsorption capacity followed the order: B-int > B-TMA > B-Cs > B-HCl > B. Using specific method of chemical modification, the acetone adsorption capacity level compared to AC was reached. Surface area (ABET) of AC was 10-times greater than ABET of B-TMA, but in comparison with B-TMA the adsorption capacity of AC was only doubled. Therefore, ABET should not be the only factor determining acetone adsorption onto modified bentonite, but also chemical character of the adsorbent surface ought to be taken into consideration. The isotherm for B-TMA was examined in the temperature of 30°C for vapor pressure range of 0 to 0.5 P/P0. In order to perform modeling of adsorption equilibrium, there were used obtained equilibrium concentrations of acetone in solid and gaseous state. Two-, three- and four-parametric empirical equilibrium models were applied. The non-linear curve fitting was carried out using the Levenberg-Marquardt algorithm. The relationship between two variables (experimental and theoretically predicted) was assessed by the Fisher test, the mean error and the approximation of standard deviation. The best criteria value of statistical tests proved that the best approximation of experimental data was obtained for the Redlich-Peterson model. Moreover, this model reflected the best approximation of experimentally obtained maximum adsorption capacity value (qm,exp). The value of parameter n (n ≠ 1) implied heterogeneity of the B-TMA adsorbent surface and/or multilayer adsorption.