Thermodynamic Study of Methylene Blue Adsorption on Carbon Nanotubes Using Isothermal Titration Calorimetry: A Simple and Rigorous Approach

Abstract

In this article, a thermodynamic study of the methylene blue (MB) adsorption on carbon nanotubes (CNT), a known model system, was carried out by using a simple and rigorous experimental approach based on adsorption and isothermal titration calorimetry (ITC) experiments. Considering the thermodynamics of the process, the classical approach using the van't Hoff approximation provided endothermic values for Δ ads H 0 while the ITC measurements revealed that the adsorption of MB on both unmodified and acid-modified CNTs is an exothermic process. The thermodynamic parameters for the systems were obtained using the infinite dilution regime and ITC data: Δ ads H 0 = −9.13 ± 0.02 kJ mol −1 , Δ ads G 0 = −21.18 ± 0.61 kJ mol −1 , and Δ ads S 0 = 40.42 ± 0.61 J K −1 mol −1 for u-CNT and Δ ads H 0 = −11.49 ± 0.34 kJ mol −1 , Δ ads G 0 = −27.88 ± 0.18 kJ mol −1 , and Δ ads S 0 = 54.97 ± 0.38 J K −1 mol −1 for f-CNT. The process is both enthalpically and entropically driven, having a more negative Δ ads G 0 for the system based on a modified nanotube. With this work, we expect to increase the interest of researchers in the study of other solid−liquid adsorption systems using calorimetric techniques and also contribute to a more accurate characterization of the thermodynamic properties without the use of an excessive number of approximations.

High value activated carbons from waste polystyrene foams

“…The maximum amounts adsorbed by AC600, AC700 and AC800 were 270, 536 and 1042 mg g -1 respectively. The AC obtained at 800 ºC evidenced an excellent adsorption performance with an outstanding amount of MB adsorbed, one of the highest, in fact, ever published in the literature (Table 2) [23][24][25][26][27][28][29][30][31][32][33].…”

“…This could also be a possible and simple solution to add value to the recycling of this material. Graphene oxide 243.9 [24] Carbon nanotubes 99.8 [26] Activated carbon 435 [27] Mesophase pitch-derived AC 950 [23] Pyrophyllite 70.4 [28] Calcium…”

Preparation of Nano-Particles and Their Applications in Adsorption

“…Among nano-particles (metal oxides), the magnetic nano-particles have acquired a substantial importance due to their interesting magnetic properties i.e. super para-magnetism, strong reaction even at minor applied magnetic field [6,12,55,56].…”

“…Moreover, a recent improvement on carboniferous and siliceous nano-materials enclosed nano-sheets, nano-tubes and nano-particles of carbon and silicon declared as efficient adsorbents for sorption of metals and dyes from wastewater. Some oxides and carbon based nanomaterials are discussed below [55][56][57].…”

Self-Recognizing π-π Stacking Interactions Designed for the Generation of Ultrastable Mesoporous Hydrogen-Bonded Organic Frameworks

“…To understand the adsorption of MB on HOF-102, isothermal titration calorimetry (ITC) experiments ( Figure S23 and Table S4) were performed, and the calculated binding affinity (K a = 3.89 ± 0.22 × 10 4 M -1 ) for MB on HOF-102 is higher than the reported value using carbon nanotube as a sorbent. 40 Figure S24). The complete adsorption of Cyt-c occurred within four hours ( Figure 4C).…”