Adsorption Study of Glycerol in Biodiesel on the Sulfonated Adsorbent

Abstract

The adsorption isotherm data of glycerol from biodiesel (FAME, fatty acid alkyl esters) onto the sulfonated adsorbent were obtained via batch equilibrium tests at different temperatures in the range of 303–323 K. Subsequently, these data were fitted by four isotherm models. Freundlich isotherm model was the best fitted (r 2 > 0.98), and the model parameter 1/n implied that the adsorption process was favorable. For the Dubinin–Radushkevich (D-R) isotherm model, the model parameter Q D decreased with increasing temperature, and the mean free energy of sorption (E) was less than 8 kJ mol–1. The results of Q D and E reflected the exothermic and physical properties of the adsorption process, respectively. The negative values of Gibbs free energy change (ΔG 0) and enthalpy change (ΔH 0) indicated that the adsorption occurs spontaneously with an exothermic nature, while the positive values of entropy change (ΔS 0) suggested the increase in randomness at the solid–liquid interface during adsorption. The isosteric heat of adsorption (ΔH X) suggested that strong hydrogen bonding between glycerol and the −SO3 – groups of the sulfonated adsorbent dominated the adsorption process and that there existed adsorbate–adsorbate mutual attractive interaction. Furthermore, the existence of hydrogen bonding was also confirmed by infrared spectra.

Synthesis and Charaterization of Silica-Based Aldehyde Chitosan Hybrid Material for Biodiesel Purification

“…Adsorbents whose capacity to remove free glycerol from biodiesel has been evaluated include, magnesium silicate (Magnesol) [ 22 , 23 ], ion exchange resins (amberlite and pyrolite) [ 23 ], sulfonated resin [ 24 ], silicas [ 25 ], eucalyptus pulp [ 26 ], sugarcane bagasse [ 27 ], and cellulose [ 28 ]. However, researchers are still looking for a low-cost material that can be used on an industrial scale removes other impurities, and can be regenerated and reused.…”

Improvement of glycerin removal from crude biodiesel through the application of a sulfonated polymeric adsorbent material

“…The stronger absorbance at 3440 cm −1 in the sulfonated PVA was due to its polar surface, which was caused by the sulfonation of the PVA material. In a comparison of Figures (d) and (e), we observed that some bands changed after sulfonation; these included the weaker absorbance at 2800–2900 cm −1 due to aromatic hydrogen atom substitution and the stronger absorbance at 690 cm −1 due to the in‐plane bending vibrations of the aromatic SO 3  groups …”

“…The sulfonation of PVA increased the efficiency of the solid material for glycerin adsorption by approximately 70%. These facts evidenced that sulfonated materials are more efficient in glycerin removal because of the strong hydrogen bonding between glycerol and the SO 3  groups of the sulfonated adsorbent . Additionally, the PVA film was easily separated from the liquid medium, so application of the sulfonated PVA film is recommended for biodiesel purification.…”

Sequential Oxygen Reduction and Adsorption for Carbon Dioxide Purification for Flue Gas Applications

“…Figure 6 shows the mechanism for O 2 removal by catalytic reduction on the surface of Pd catalyst using CH 4 . [33] The reactants, CH 4 and O 2 , first undergo dissociative adsorption on the Pd surface (denoted by an asterisk). Propagation reactions lead to further C-H cleavage and the formation of more stable O-H and C-O bonds.…”