Abstract
The worldwide production of colored products and intermediates is increasing year on year. The consequence of this is an increase in the number of liquid effluents containing toxic dyes entering the aquatic environment. Therefore, it is extremely important to dispose of them. One of the techniques for the elimination of environmentally harmful dyes is adsorption. The main purpose of this study was to explore the possibility of using a carbon and silica (C/SiO2)-based composite for the removal of the azo dye C.I. Basic Red 46 (BR46). The adsorption capacity of C/SiO2 was found to be temperature dependent and increased from 41.90 mg/g to 176.10 mg/g with a temperature rise from 293 K to 333 K in accordance with the endothermic process. The Langmuir isotherm model seems to be the better one for the description of experimental data rather than Freundlich or Dubinin–Radushkevich. The free energy (ΔGo) confirmed the spontaneous nature of BR46 adsorption by C/SiO2. Kinetic parameters revealed that BR46 uptake followed the pseudo-second-order equation; however, the external diffusion plays a significant role. Surfactants of cationic, anionic and non-ionic type influenced BR46 retention by C/SiO2. The electrokinetic results (solid surface charge density and zeta potential) indicated that the adsorption of cationic dye and surfactant influences the structure of the electrical double layer formed at the solid–liquid interface.
Highlights
Dyes are organic substances that are used in many areas of industry such as: textiles, paper, tanning, cosmetics and food industries
This paper describes the adsorption properties of the carbon-and-silica-based composite towards basic dye
This paper presented the adsorptive properties of the carbon–silica composite towards toxic azo dye, i.e., C.I
Summary
Dyes are organic substances that are used in many areas of industry such as: textiles, paper, tanning, cosmetics and food industries. The most popular adsorbents are materials based on activated carbon due to its developed specific surface area and high porosity, as well as high efficiency in the removal of dyes from wastewater [9] They possess a number of favorable properties, among which are resistance to high temperatures in non-oxidizing atmospheres, chemical stability, resistance to drastic temperature changes, or low coefficients of thermal expansion [10]. It was shown that carbon–silica composite presents high efficiency for Cu(II) adsorption from a solution containing proteins with a different internal stability (ovalbumin and lysozyme) [18] as well as ionic polyacrylamides [19] Waste material such as fly ash (consisting of unburned carbon, silica, alumina and iron oxide) was used for the separation of copper, nickel and cadmium ions in the presence of methylene blue dye [20]
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