Gas cylinder 2. Mass flow meter 3. VOCs generator 4. Mixing bottle 5. Adsorbent bed 6. GC-MS 7. Tail gas absorption. The adsorption volume of VOCs is calculated by integrating the adsorption curve.
The mathematical expression is as follows:. W is the quality of the adsorbent, in g. The impurities include S, K, and Fe, which accounts for 0. It indicates that the prepared zeolite X sample is of high purity.
Since EDS is primarily directed to the specific space of zeolite, it is commonly used to characterize individual particles or local samples. As can be seen from the figure, there is almost no amorphous peak in the XRD diffraction pattern of the zeolite X, which indicates that the zeolite X is of good crystallinity and no other crystals are formed.
The specific surface area and pore structure are important indicators to evaluate zeolite. The BET specific surface area of the synthesized zeolite X is The microscopic morphology can reflect the crystallinity of the material. It can be seen that the crystal form of the zeolite X is mainly octahedral structure. The surface of the partial particle unit cell is rough and has some defects.
It may be that the aluminosilicate ions are not completely dissolved in water and some of the ions are still adsorbed on the surface of the particles during the hydrothermal reaction. It also may be due to the presence of Ca, K impurities in the mother liquor. The time from the start of adsorption to the penetration point is the penetration time.
The capacity of adsorption during the penetration time is penetration adsorption capacity. The time from the start of adsorption to the adsorption saturation is the saturation time. The capacity of adsorption during the saturation time is the saturated adsorption capacity. The physical parameters of VOCs are shown in Table 4. The adsorption of isopropyl alcohol, benzene and cyclohexane was tested by the zeolite X and activated carbon and then comparing the adsorption properties of two adsorbents.
As is shown in the picture, the adsorption curve of zeolite X lags behind that of activated carbon and the adsorption capacity of zeolite X on VOCs is larger than activated carbon, which indicates that zeolite X has better adsorption performance than activated carbon.
Original Research ARTICLE
The adsorption capacity of isopropanol is higher than that of benzene and cyclohexane, whether zeolite X or activated carbon Figures 8 — 10 ; Tables 5 , 6. The adsorption performance of the adsorbent is closely related to the polarity of the molecules. The polarity of isopropanol is stronger than that of benzene and cyclohexane. In addition, the unsaturation of molecules is also an important factor to determine the adsorption performance of adsorbent.
The greater unsaturation of the molecules and the stronger adsorption capacity of the adsorbent. A large number of micropores are formed in the process of disorderly superposition of adjacent graphite microcrystals and the pore diameter of activated carbon micropore is between 0. The activated carbon has large specific surface area due to its unique pore structure characteristics Chmelik et al.
The carbon atoms on the surface are easily oxidized with hydrogen and oxygen to form various functional groups due to covalent bond unsaturation in the preparation of activated carbon. Therefore, the polarity of activated carbon has significant effect on its adsorption properties Bhatnagar et al. Zeolite X has the function of screening molecules. Uniform pore size and honeycomb structure are the unique characteristics of zeolite X. The adsorbate can be captured when its molecular diameter is smaller than the zeolite X aperture Zhou et al.
The framework of the zeolite X carries negative charge because the silicon atoms are replaced by aluminum. The negative charge is compensated by strongly polar molecules outside the framework of the zeolite X. The greater polarity of the adsorbate molecules and the higher adsorption capacity of the zeolite X Akosman and Kalender, ; Gorshunova et al.
Adsorbate molecules are activated due to special electric field effects in the pore channels of zeolite X, which ensures that the zeolite X can identify the adsorbate molecules accurately and improve the adsorption performance of the zeolite X Akosman and Kalender, ; Kim and Ahn, Brosillon et al.
The results showed that the adsorption capacity of zeolite to heptane was larger than that of acetone. The molecular polarity of heptane is stronger than acetone, which reflects the excellent selectivity of zeolite and it is closely related to the molecular polarity of VOCs Brosillon et al. The comprehensive utilization of coal fly ash can not only develop circular economy, but also produce huge environmental and social benefits. At present, China's economy is developing at high speed and the demand for resources is also increasing as well. The refinement and high value-added comprehensive utilization of coal fly ash resources should be the prospect in the future and it is an important way to achieve sustainable development strategies in China.
This study may bring a new and alternative approach for recycling of coal fly ash.
Reviews on Environmental Health
By analyzing the chemical phase, microstructure and VOCs adsorption performance of zeolite X and activated carbon, it was found that:. There is no need to add silicon or aluminum source during the synthesis process. It effectively enhances the comprehensive utilization efficiency of the coal fly ash and enriches the product categories.
The crystalline form is mainly octahedral structure and the particle size distribution is basically uniform.
Environmental Chemistry | LAQV
The structure and microstructure specific of zeolite X are analyzed. The results show that the BET specific surface area is The adsorption capacity of cyclohexane on zeolite X is higher than that on benzene and isopropanol. All authors have contributed in various degrees to the analytical methods used, to the research concept, to the experiment design, to the acquisition of data, or analysis and interpretation of data, to draft the manuscript or to revise it critically for important intellectual content.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Akosman, C. Analysis of diffusion and adsorption of volatile organic compounds in zeolites by a single pellet moment technique. Bhatnagar, A. An overview of the modification methods of activated carbon for its water treatment applications.
Brihi, T. Determining volatile organic compounds' adsorption isotherms on dealuminated Y zeolite and correlation with different models. Data 47, — Brosillon, S. Brunchi, C. C, and Stankiewicz, A. Adsorption of volatile organic compounds. Experimental and theoretical study. Calero, S. On the performance of FAU and MFI zeolites for the adsorptive removal of a series of volatile organic compounds from air using molecular simulation. Chiang, P. Effects of pore structure and temperatuare on VOC adsorption on activated carbon.
Casey C. Chakhmouradian A. Chambers E. Midwinter, London.
Chandler D. Chawla N.
Chen J. Choptuik M.
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