Adsorption Capacity of Smectite Clay and Its Thermal and Chemical Modification for Two Anionic Dyes: Comparative Study

Abstract

The present research evaluates the influence of modification of smectite clay (BC) on its adsorption capacity of anionic dyes from aqueous solutions. Thermal (BC 250), acidic (BC H2SO4), and alkaline (BC NaOH) modification of clay was carried out. The clays were characterized by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Adsorption of dyes was investigated by batch experiments at room temperature (23 ± 2 °C), a wide range of initial dye concentrations (1–1000 mg/dm3), and an adsorbent dose of 50 g. All modifications increased the clay’s adsorption capacity for Reactive Red 198, in the order BC H2SO4 > BC NaOH > BC 250 > BC; it was 10.32, 5.06, 3.32, and 2.92 mg/g, respectively. Acid and thermal modification of the clay increased its adsorption capacity for Acid Red 18, in the series BC H2SO4 > BC 250 > BC > BC NaOH; it was 3.07, 2.66, 2.16, and 1.28 mg/g, respectively. The experimental data were analyzed by Freundlich, Langmuir, Dubinin–Radushkevich, and Sips isotherms, using nonlinear regression. The experimental data best fitted the Sips isotherm. Taking into account the structure of the adsorbent and adsorbates and the results obtained, it can be concluded that the dyes were probably bound through chemisorption, by forming hydrogen bonds between Si–OH and Al–OH groups in the clay and –NH, –NH2, and –OH groups in the dyes. From the results obtained, it can be concluded that smectite clay is a promising material for dye adsorption.

Synthesis and Micromechanistic Studies of Sensitized Bentonite for Methyl Orange and Rhodamine-B Adsorption from Wastewater: Experimental and DFT-Based Analysis

“…Langmuir and Freundlich’s isotherms were applied here to investigate the adsorption data ( Figure 6 ). The primary supposition of the Langmuir model is that a monolayer forms on the adsorbent’s surface, meaning that a single dye molecule may be adsorbed on one adsorption site and that forces between molecules diminish with distance [ 39 ]. It was also expected that the surface of the adsorbent would be homogenous and have comparable and energetically similar adsorption sites ( Figure 6 a) [ 40 ].…”

Enhanced Adsorption Capacity of Methylene Blue Dye onto Kaolin through Acid Treatment: Batch Adsorption and Machine Learning Studies

“…Various procedures and treatment methods have been employed throughout the last years for removing dyes from wastewater sources. Among current methods such as chemical oxidation [19], filtration [20], coagulation-flocculation [21], ozonation [22], membrane processes [23], biological treatment [24], precipitation, ion exchange [25], and photocatalytic degradation [26], adsorption is one of the most commonly used techniques for treating textile dye pollutants in water [27][28][29][30]. This is because of its low cost, ease of use, high efficiency, availability, and simple design, as well as its ability to handle a wide range of pollutants and adsorbents.…”

“…These factors make adsorption a more attractive option compared to the other approaches [3,7,9,11,27,28]. In the literature, many absorbents were used for the removal of pollutants from the environment, such as graphene/montmorillonite [29], chitosan/clay [6], bentonite [16], alginate beads [14], smectite [30], zeolite [31], and activated carbon [27]. Among them, clays are widely used as adsorbents due to their inexpensive cost, specific surface area, excellent stability, and variety of properties.…”

Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane

“…Dyes can be classified based on their charge, functional groups, and usefulness. On the basis of chemical structures, they can be classified into azo, anthraquinone, indigoid, nitro, triarylmethane, and so forth, and based on their use, they may be classified as cationic dyes, anionic dyes, and nonionic dyes. , The most significant aspect of these dyes is their charge, as it impresses the productiveness of the adsorption process . Methyl orange (MO) is a primarily employed dye from the azo group, which also has very low biodegradability and thus can persist in the environment for an extended period of time.…”