An analysis of gas chromatography pulse dispersion data for the system n-butanelzeolite NaY is presented. The data were analyzed in terms of two models, an intracrystalline diffusion limiting model and a surface barrier model. Both models provided acceptable fits to the pulse dispersion data; however, the temperature dependence of the apparent mass transport parameters strongly suggests that a surface barrier is responsible for the observed transport resistance. The Henry's law constants were independent of choice of model and the isosteric heat of sorption was consistent with literature values. Chen-Chen SCOPEThere are indications in the literature that diffusion measurements in zeolites by the sorption rate technique may under certain circumstances be controlled by a surface barrier resistance. This is most likely to occur for rapid diffusion in small crystals of large-pore zeolites. However, another phenomenon must be considered in analyzing such systems, namely the sorption heat effect. Failure to take into account either the surface barrier or the sorption heat effect will result in erroneously low reported values of intracrystalline diffusivity. It is important to distinguish between these effects because of the many applications of large-pore zeolites in industry.Pulse gas chromatography offers a potential means for eliminating the sorption heat effect, and at the same time it should be sensitive to a surface barrier. In the present study we have undertaken a study of n-butane sorption and diffusion on a commercial sample of zeolite Nay. The data are analyzed on the basis of an intracrystalline diffusion model and a surface barrier model. We earlier reported results on the n-butanelNaY system, but it was not possible to obtain quantitative results due to a system nonlinearity (Hsu and Haynes, 1981). This problem was eliminated in the present study by using much more sensitive detectors. CONCLUSIONS AND SIGNIFICANCEBy injecting highly diluted n-butane pulses into our system it was possible to operate in a linear region where complications from nonlinear sorption, non-fickian diffusion and sorption heat effects were absent. Henry's law constants were independent of the choice of model, and the isoteric heat of sorption compared favorably with literature values on a similar zeolite (NaX). It was not possible t o distinguish between anCorrespandencz concerning this paper should be addressed to H. W. Haynca. Jr. 1848November 1986 intracrystalline diffusion model and a surface barrier model on the basis of goodness of fit. However, arguments based on the apparent activation energies support the surface barrier model. Furthermore, it appears that the surface barrier is due to a finite rate of adsorption from the gas phase, as opposed to pore constrictions just under the zeolite crystal surface. This interpretation leads to the conclusion that the sticking coefficient for molecules colliding with the external surface is of the order of lo-'. Such a small value of the Vol. 32, No. 11 AICbE Journal sticking coeff...

A dynamic model is derived for simultaneous, homogeneous and heterogeneous, first-order reactions in a slurry reactor. The theory is applied to experimental data for the oxidation (with gaseous oxygen) of aqueous sulfite solutions which is first order in oxygen and zero order in sulfite. The homogeneous reaction is very slow at low pH (2-3) where the sulfur exists as dissolved SO, or HS03-, even when cobalt is added as a homogeneous catalyst. At higher pH (7-8.5), considerable homogeneous reaction occurs with and without cobalt ions. Here the predominant species are SO3' and HS03-. Activated carbon is not a heterogeneous catalyst at pH 7 or 8.5, but is responsible for nearly all the reaction at the low pH values. Analysis of the heterogeneous data indicates that the surface reaction between adsorbed oxygen and SO2 controls the rate rather than adsorption of oxygen.

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Osmanthus fragrans (scientific name: Osmanthus fragrans (Thunb.) Lour.) is a species of the Osmanthus genus in the family Oleaceae, and it has a long history of cultivation in China. O. fragrans is edible and is well known for conferring a natural fragrance to desserts. This flowering plant has long been cultivated for ornamental purposes. Most contemporary literature related to O. fragrans focuses on its edible value and new species discovery, but the functional use of O. fragrans is often neglected. O, fragrans has many properties that are beneficial to human health, and its roots, stems, leaves, flowers and fruits have medicinal value. These characteristics are recorded in the classics of traditional Chinese medicine. Studies on the metabolites and medicinal value of O. fragrans published in recent years were used in this study to evaluate the medicinal value of O. fragrans. Using keywords such as metabolites and Osmanthus fragrans, a systematic and nonexhaustive search of articles, papers and books related to the medicinal use of Osmanthus fragrans metabolites was conducted. Fifteen metabolites were identified through this literature search and classified into three categories according to their properties and structure: flavonoids, terpenes and phenolic acids. It was found that the pharmacological activities of these secondary metabolites mainly include antioxidant, anticancer, anti-inflammatory and antibacterial activities and that these metabolites can be used to treat many human diseases, such as cancer, skin diseases, cardiovascular diseases, and neurological diseases. Most of the reports that are currently available and concern the secondary metabolites of Osmanthus fragrans have limitations. Some reports introduce only the general classification of compounds in Osmanthus fragrans, and some reports introduce only a single compound. In contrast, the introduction section of this paper includes both the category and the functional value of each compound. While reviewing the data for this study, the authors found that the specific action sites of these compounds and their mechanisms of action in plants are relatively weak, and in the future, additional research should be conducted to investigate this topic further.

Atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-s-triazine) is a selective herbicide that has been widely used worldwide due to its low cost and good weeding effect. However, owing to the characteristics such as stable chemical structure, superficial mobility, long half-life and high leaching potential, atrazine has been frequently detected in the surface and ground water in many countries and regions [1-3]. Continuous exposure to atrazine may inhibit the growth of plants and animals. Moreover, atrazine can be absorbed and accumulated by the human body through food chain enrichment, which would disrupt the endocrine systems, alter immune response, retard sexual and embryo development and induce the mammary gland or cancer [4, 5]. Therefore, the removal of atrazine from water