Removal of Methyl Red from Aqueous Solution Using Biochar Derived from Fennel Seeds

Abstract

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor to obtain carbon adsorbents through physical activation with carbon dioxide and chemical activation by impregnating the precursor with sodium carbonate. The physical activation involved the carbonization of the precursor at a temperature of 600 °C for 60 min and activation at a temperature of 800 °C for 30 min with carbon dioxide. Chemical activation included impregnation of the precursor with sodium carbonate at a mass ratio of a precursor to activator of 1:2. The mixture was activated in a nitrogen atmosphere with a flow rate at a temperature of 700 °C for 45 min. The resulting biochar samples were washed with 5% hydrochloric acid and subsequently rinsed with boiling distilled water. The biochar adsorbents were characterized using low-temperature nitrogen adsorption–desorption isotherms, Boehm titration, and pH measurements of their aqueous extracts. The specific surface area of the obtained adsorbents ranged from 89 to 345 m2/g. Biochar adsorbents exhibit a predominance of acidic groups over basic groups on their surfaces. The sorption capacities of the obtained samples towards an aqueous solution of methyl red range from 26 to 135 mg/g. Based on adsorption studies, it was found that the adsorption of the dye on the obtained biochar materials follows a pseudo-second-order model. The Freundlich isotherm best describes the studied process, indicating the formation of a multilayer of adsorbate on the adsorbent surface. The efficacy of adsorption in aqueous solutions of methyl red was found to increase with the elevation of the process temperature. Moreover, thermodynamic studies have shown that the adsorption process is spontaneous and endothermic. Consequently, this work provides a description of the physicochemical parameters of two biochars obtained by physical and chemical activation of a little-studied precursor—fennel seeds—and studies on their potential use as adsorbents for contaminants from the aqueous phase.

Methyl Red Adsorption on Biochar Obtained by Physical Activation of Caraway Seeds with Carbon Dioxide

“…Considering the surface analysis of the carbon materials tested, it can be concluded that there are several mechanisms by which methyl red can be adsorbed on the surface of biochar. Interactions between an adsorbent and adsorbate can occur through electrostatic attraction to a positively or negatively charged surface, π–π interactions involving aromatic rings or hydrogen bonds [19] …”

“…Interactions between an adsorbent and adsorbate can occur through electrostatic attraction to a positively or negatively charged surface, π-π interactions involving aromatic rings or hydrogen bonds. [19] Table 2 displays the acid-base properties of the biochar samples. The precursor exhibits a slightly acidic surface property, as evidenced by a pH value of 6.6 in its aqueous extract.…”

A Study on the Adsorption of Rhodamine B onto Adsorbents Prepared from Low-Carbon Fossils: Kinetic, Isotherm, and Thermodynamic Analyses

“…A PlasmaQuant PQ 9000 Elite spectrometer (Analytic, Jena, Germany) was used. The measurement procedure is described in our earlier work [ 34 ]. The concentration of oxygen functional groups on the surface of the activated carbons was assessed using the Boehm method [ 16 ].…”

Aminated Rapeseed Husks (Brassica napus) as an Effective Sorbent for Removing Anionic Dyes from Aqueous Solutions

“…One of the simplest and most effective methods for removing dyes from post-production water is adsorption [ 4 ], which involves binding dye molecules on the sorbent’s surface. The most popular sorbents today include activated carbons [ 5 ], which consist mainly of elemental carbon, the characteristic feature of which is a very extensive surface area, exceeding 500 m 2 /g [ 6 ]. These sorbents have been proved effective in removing most industrial dyes [ 7 ].…”