Review of adsorbents incorporating calixarene derivatives used for metals recovery and hazardous ions removal: the concept of adsorbent design and classification of adsorbents

Kaolin-Derived Porous Silico-Aluminate Nanoparticles as Absorbents for Emergency Disposal of Toluene Leakage

To rapidly eliminate toluene from aqueous environments during leakage accidents, this paper synthesized porous silico-aluminate nanoparticles (SANs) via a hydrothermal method, using cost-effective and non-toxic natural kaolin as the basic raw material. The morphology and structure of the porous SANs were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and BET-specific surface area tests. The effects of different conditions, such as the dosage of porous SANs, initial concentration of toluene, temperature, capture time, and pH, on the adsorption performance of porous SANs were analyzed. The as-prepared SANs exhibited a high removal efficiency and rapid adsorption performance toward toluene in aqueous solution. Finally, the kinetics of the adsorption of toluene in aqueous solution by porous SANs were investigated. The mechanism of the adsorption of toluene by porous SANs was further discussed. These findings provide a cost-effective and highly efficient absorbent for the emergency disposal of toluene leakage accidents.

Utilization of vanillin to prepare sulfated Calix[4]resorcinarene as efficient organocatalyst for biodiesel production based on methylation of palmitic acid and oleic acid

Recently, biodiesel production from palm oils has been thoroughly investigated to substitute crude oil due to its scarcity. However, the biodiesel production process is time-consuming due to its slow kinetics; thus, concentrated sulfuric acid has been used to fasten the reaction process in some industries. Unfortunately, sulfuric acid is a toxic, corrosive, and non-environmentally friendly catalyst. In this study, we prepared sulfated Calix[4]resorcinarene derived from vanillin as an efficient organocatalyst to replace sulfuric acid. The catalytic activity of sulfated Calix[4]resorcinarenes was evaluated through the methylation of palmitic acid and oleic acid as model compounds due to their abundant amounts in palm oil. The Calix[4]resorcinarene and sulfated Calix[4]resorcinarenes have been obtained through a one-pot reaction in 71.8-98.3% yield. Their chemical structures were confirmed by using FTIR, NMR and HRMS spectrometry analyses. The results showed that the sulfated Calix[4]resorcinarene exhibited high catalytic activity for methyl palmitate and methyl oleate productions in 94.8 ± 1.8 and 97.3 ± 2.1% yield, respectively, which was comparable to sulfuric acid (96.3 ± 1.8 and 95.9 ± 2.5%). The optimum condition was achieved by using 0.020 wt equivalent of organocatalyst for 6 h reaction process at 338 K. The methylation of palmitic acid and oleic acid fits well with the first-order kinetic model (R² = 0.9940-0.9999) with a reaction rate constant of 0.6055 and 1.1403 h^-1, respectively. Further investigation reveals that the hydroxyl group of vanillin plays a pivotal role in the organocatalytic activity of sulfated Calix[4]resorcinarene.

Comparative Extraction of Aluminum Group Metals Using Acetic Acid Derivatives with Three Different-Sized Frameworks for Coordination

We prepared acetic acid derivatives using three different frameworks, calix[4]arene, alkenyltrimethylol, and trihydroxytriphenylmethane, which differ in the number and size of their coordination sites. We further investigated the extraction properties for aluminum group metal ions. All three extraction reagents exhibited increased extraction compared with the corresponding monomeric compounds, owing to structural effects. The extraction reaction and extraction equilibrium constants were determined using a slope analysis. Their extraction abilities, separation efficiencies, and potential coordination modes are discussed using the extraction equilibrium constants, half-pH values, and spectroscopic data. The calix[4]arene and trihydroxytriphenylmethane derivatives demonstrated allosteric co-extraction of indium ions (In3+) with an unexpected stoichiometry of 1:2.