Development of dual-model classical density functional theory and its application to gas adsorption in porous materials

Classical density functional theory (CDFT) is a useful theory in many fields. The basis of CDFT is spherical model and extending it to nonspherical molecules is a challenging issue due to the orientation/configuration of the molecules, which implies more complicated molecular models, and higher computational costs. In this work, we propose a dual-model classical density functional theory (DM-CDFT) to address this issue. The theory uses a more precise model (all-atom model) and a simpler model (coarsening model) to construct the external and excess free energy functionals, respectively. By using this methodology, CDFT could handle orientation/configuration effects with low computational costs. The theory is examined by applying it to gas adsorption (such as C₂H₂/C₂H₄/C₂H₆ and toxic gases) in porous materials, and the predicted adsorption isotherms verify the accuracy of the theory. Additionally, the predicted density profile indicates that rotation entropy plays an important role in the adsorption of nonspherical molecules.     

Comparative study of the textural characteristics of oil palm shell activated carbon produced by chemical and physical activation for methane adsorption

The objective of this study is to relate textural and surface characteristics of microporous activated carbon to their methane adsorption capacity. Oil palm shell was used as a raw material for the preparation of pore size controlled activated carbon adsorbents. The chemical treatment was followed by further physical activation with CO₂. Samples were treated with CO₂ flow at 850 °C by varying activation time to achieve different burn-off activated carbon. H₃PO₄ chemically activated samples under CO₂ blanket showed higher activation rates, surface area and micropore volume compared to other activation methods, though this sample did not present high methane adsorption. Moreover, it was shown that using small proportion of ZnCl₂ and H₃PO₄ creates an initial narrow microporosity. Further physical activation grantees better development of pore structure. In terms of pore size distribution the combined preparation method resulted in a better and more homogenous pore size distribution than the conventional physical activation method. Controlling the pore size of activated carbon by this combined activation technique can be utilized for tuning the pore size distribution. It was concluded that the high surface area and micropore volume of activated carbons do not unequivocally determine methane capacities.     

A simple determination method of the absolute adsorbed amount for high pressure gas adsorption

A new determination method of the absolute adsorbed amount is proposed. The present method, which is called the buoyancy-mediated (BM) method, is simpler than the adsorbed volume mapping (AVM) method [Chem. Phys. Lett., 321 (2000) 342]. If there are data of the experimental surface excess mass up to the high pressure region, the BM method coincides with the AVM method. In the case of methane adsorption on pitch-based activated carbon fiber (ACF: P-5), the obtained volume of the adsorbed layer is from 0.84 to 20 ml/g. The isosteric heat of adsorption from the absolute adsorption isotherms is in the range of 19 to 25 kJ/mol, which almost coincides with the value calculated from grand canonical Monte-Carlo simulation.     

Ordered mesoporous carbon preparation by the in situ radical polymerization of acrylamide and its application for resorcinol removal

In this study, acrylamide (AM) was, for the first time, successfully used to synthesize ordered mesoporous carbon (OMC) through in situ polymerization inside SBA‐15 (Santa Barbara Amorphous type material) as a hard template. A straightforward and environmentally friendly method was proposed and verified with an emphasis on the precursor modification for the preparation of OMC. The influences of the structure and the amount of SBA‐15 on the OMC structure and adsorption capacity were evaluated. To improve the adsorption capacity and yield, the following three approaches were tried: (1) the use of concentrated sulfuric acid (H₂SO₄) to fix carbon and nitrogen, (2) the use of a crosslinking agent, and (3) the addition of melamine as a possible nitrogen source. The adsorption capacities for resorcinol were evaluated, and they showed an improvement of 37% in comparison with that of the commercially available granular activated carbon (27 mg/g). Well‐OMC materials were obtained with higher yields with H₂SO₄ and crosslinking agent compared with those obtained for the pure AM precursor. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43426.     

等离子体引发微孔板接枝SMCC及蛋白吸附性能

用丙烯酰胺等离子体引发活化聚苯乙烯（PS）微孔板，接枝4-(N-马来酰亚胺基甲基)环己 烷-1-羧酸琥珀酰亚胺酯（SMCC）联接剂，制备了易于固定蛋白的PS-g-SMCC微孔板。利用FTIR、EDS、XPS、SEM、接触角测试仪和酶标仪对其表面组成、结构、形貌及蛋白吸附性能进行了表征。结果表明，PS微孔板表面成功接枝了丙烯酰胺与SMCC，当等离子体处理参数为500 W，300 s时，接枝丙烯酰胺的效果最好，PS-g-SMCC微孔板表面达到超亲水；当SMCC质量浓度为5 g/L 时，PS-g-SMCC微孔板对牛血清蛋白的吸附量最大，为903.08 ng/cm2，与未处理的PS微孔板相比，吸附量提高了2.93倍，有效提高了PS微孔板的检测灵敏性。     

Bamboo charcoal modified with Cu2+ and 3-aminopropyl trimethoxy silane for the adsorption of acid fuchsin dye: Optimization by response surface methodology and the adsorption mechanism

The bamboo charcoal modified with Cu²⁺ and 3-aminopropyl trimethoxy silane (BC-Cu/Si-NH₂) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and surface acid–base potentiometric titration. The adsorption for acid fuchsin (AF) dyes onto BC-Cu/Si-NH₂ was investigated. Moreover, response surface methodology was performed to optimize the process parameters including pH, initial dye concentration, adsorbent dosage, and temperature. The results presented that the adsorption process was mainly influenced by initial AF concentration and adsorbent dosage. Isotherm studies revealed that the adsorption data fitted well with the Sips model and Dubinin–Radushkevich (D–R) model, which indicated the monolayer, homogeneous, and physical nature of the adsorption process. The maximum adsorption capacity calculated from D–R model could approach approximately to 14.91 mg g⁻¹ at 40 °C, and the maximum adsorption capacity of Sips reached to 10.77 mg g⁻¹ at 40 °C. The kinetic experimental data matched well with Spahn and Schlunder model as well as pseudo-second-order model. In addition, intraparticle diffusion was not the only rate-controlling step of adsorption process. Thermodynamic parameters revealed the feasibility, spontaneity, and endothermic nature of adsorption. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47728.