Assessment of the Porous Structure and Surface Chemistry of Activated Biocarbons Used for Methylene Blue Adsorption

Abstract

In the presented research, activated carbons from wheat bran were obtained as a result of pyrolysis and physical activation (CO2 or/and steam). In addition, the obtained materials were subjected to additional modification with superheated steam using the microwave radiation as an energy source. The detailed materials characterization was performed using low-temperature nitrogen adsorption/desorption, Raman spectroscopy, X-ray diffraction, thermal analysis (TG), Boehm’s titration, point of zero charge (pHpzc), scanning electron microscopy (SEM) and FT-IR/ATR methods. Moreover, the sorption capacity towards methylene blue (MB) was determined. The activated carbons were characterized with a well-developed surface and pore structure (SBET = 339.6–594.0 m2/g; Vp = 0.157–0.356 cm3/g). Activation in the presence of steam and additional modification with microwave radiation resulted in much better development of the porous structure (SBET = 600.4 m2/g; Vp = 0.380 cm3/g). The materials were shown to possess amorphous structure and thermal stability up to the temperatures of ~450–500 °C. They have good adsorption capacity towards MB varying from 150 mg/g to 241 mg/g depending on activation manner. The adsorption can be described by the pseudo-second order model (R2 = 0.99) and fitted to the Langmuir isotherm.

Adsorption of Methylene Blue Dye by Cetyltrimethylammonium Bromide Intercalated Polyaniline-Functionalized Montmorillonite Clay Nanocomposite: Kinetics, Isotherms, and Mechanism Study

“…In addition, the highest adsorption capacities of 81.25 mg•g −1 and 57.36 mg•g −1 were achieved by CTAB-Mt and Mt, respectively, at an MB dye concentration of 150 mg•L −1 . The reason for this trend could be that the initial dye concentration provided a considerable driving force to reduce the resistance of mass transfer between the aqueous and solid phases, and the equilibrium was achieved by introducing of the dynamic balance between the dye concentration and the adsorbent surface [21,22]. Interestingly, the removal capacity of PAni@CTAB-Mt was almost the highest among the adsorbents reported in previous studies for MB (Table 5).…”

“…The second stage includes the gradual diffusion of the adsorbate through the pores of the adsorbent (intraparticle diffusion). Finally, the third stage is an equilibrium state involving very slow diffusion of the adsorbate from the larger pores to the smaller ones (micropores) [21]. Similarly, the ID model data in Table 4 have a low regression coefficient (R 2 ), and the C parameters have positive values and they are different from zero.…”

“…In order to investigate the mechanism controlling the kinetics of the dye adsorption process on the obtained materials, the ID model proposed by Weber-Morris [21] was used. It is possible to determine the mechanism of the adsorption process in a given system.…”

Preparation of Activated Biocarbons from Cones and their Potential Application for Adsorption of Antibiotics (Tetracycline)

“…The higher the n value, the stronger the interactions between the TC molecules and the surface of the biocarbon. [15,43] To understand fully the adsorption nature there were determined the following functions describing thermodynamics of studied adsorption processes: free enthalpy (ΔG, kJ mol À 1 ), enthalpy (ΔH, kJ mol À 1 ) and entropy (ΔS, J K À 1 mol À 1 ). [44] Table 4.…”

Effect of pyrolysis temperature and hydrothermal activation on structure, physicochemical, thermal and dye adsorption characteristics of the biocarbons

“…One of the main problems of wastewater treatment is dyes and heavy metals removal. [14,15] Dyes are synthetic or natural compounds characterized by complex, aromatic structures of the molecules. They are considered toxic, carcinogenic, non-biodegradable, and environmentally dangerous substances, therefore, their removal from wastewater and water is a very important undertaking.…”