Importance of the α_s-plot Method in the Characterization of Nanoporous Materials

Abstract

In this work, an exhaustive study of the calculation of micropore and mesopore volumes with α s-plot method as proposed by Professor Sing is carried out. The method is critically compared with other similar methods such as the Dubinin-Radushkevich, t-plot and those based on density functional theory (DFT). For comparison purposes, several nanoporous materials with different chemical properties were selected. The analysis was segregated into three categories: (i) microporous materials, in which the analyzed samples are activated carbons (ACs) with different pore-size distributions, a single-walled carbon nanotube (SWNT) and a zeolite (MS5A); (ii) mesoporous materials, including ordered mesoporous carbons (CMK-3) and ordered mesoporous siliceous materials (MCM-41 and SBA-15); and (iii) micro-mesoporous materials, in which pillared clays (PILCs) obtained with different metals (Al, Si, Fe and Zr) were studied. To apply the α s-plot method, several standard isotherms previously reported by other authors were considered for the analysis of microporous and mesoporous materials. Furthermore, a series of four reference materials for PILCs were synthesized and their high-resolution nitrogen adsorption isotherms were measured and reported. The results obtained by the α s-plot method are consistent with those obtained by DFT methods. This consistency highlights the importance of the use of this reliable and versatile method, where the correct selection of the standard isotherm is the most critical aspect to be considered.

Removal of Ciprofloxacin from Aqueous Solutions Using Pillared Clays

“…The specific surface area (S BET ) was assessed by the Brunauer, Emmet and Teller (BET) method, using the Rouquerol’s criteria [ 38 ]. The micropore volumes (V μp ) were calculated with the α-plot method using the corresponding sample calcined at 1000 °C as reference material [ 39 ]. The total pore volume (V T ) was obtained using the Gurvich rule (at 0.97 of relative pressure) [ 38 ].…”

Influence of pH and antibiotic solubility on the removal of ciprofloxacin from aqueous media using montmorillonite

“…The specific surface area (BET area, S BET ) was assessed by the Brunauer, Emmet and Teller (BET) method. The micropore volumes (V μp ) were calculated with the α-plot method using the calcined sample at 1000°C as reference (Villarroel-Rocha et al, 2013). The total pore volume (V T ) was obtained by the Gurvich rule (at 0.97 of relative pressure) (Rouquerol et al, 1999).…”

Natural and Modified Montmorillonite Clays as Catalysts for Synthesis of Biolubricants

“…Samples were previously degassed at 150 °C for 12 h. The specific surface area of the samples was estimated using the Brunauer, Emmet and Teller (BET) method [ 28 ], and the total pore volume was obtained from the N 2 adsorption data at relative pressure of 0.95. Micropore volume (V µP ) was evaluated with the α S -plot method using the natural clay and pillared clay reference materials reported elsewhere [ 29 ].…”