Chitosan with Sulfonic Groups: A Catalyst for the Esterification of Caprylic Acid with Methanol

Esterification of caprylic acid with methanol was performed over chitosan with sulfonic acid groups, as a catalyst, at 60 °C. The sulfonic acid groups were introduced into chitosan (CH) by using chlorosulfonic acid. Catalysts were characterized by scanning electron microscopy (SEM), elemental analysis, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and acid–base titration. Catalytic activity increased with the amount of sulfonic acid groups present on chitosan. The 4–CH–SO3H catalyst (chitosan with sulfonic acid groups—sample 4 prepared) showed the highest activity of all materials. The esterification of caprylic acid with methanol was optimized using a 4–CH–SO3H catalyst. Under optimized reaction conditions, it was found that, at 60 °C, with 0.2 g of catalyst loading and with a molar ratio methanol to caprylic acid equal 1:95, a caprylic acid conversion of about 83%, after 4 h could be obtained. Catalytic stability of the 4–CH–SO3H material was evaluated through consecutive batch runs. After the second batch, the catalytic activity stabilized.

Enhancing Anti-Static Performance of Fibers by Construction of the Hybrid Conductive Network Structure on the Fiber Surface

The hybrid antistatic agent SCNTs/OAA composed of sulfonated carbon nanotubes (SCNTs) and organic antistatic agent (OAA) was treated on the fiber surface to construct the hybrid conductive layer. Among them, SCNTs were synthesized through a simple method, and their chemical structure and morphology were characterized. SCNTs had good dispersibility due to the presence of sulfonic acid groups, which made SCNTs uniformly dispersed on the fiber surface. The SCNTs/OAA-treated fiber was hardly affected by relative humidity, because SCNTs form a continuous and uniform physical conductive network on the fiber surface. When the addition amount of SCNTs/OAA was 0.5~2 wt%, the fiber had excellent antistatic ability. Under the synergistic effect of SCNTs and OAA, the resistivity of SCNTs/OAA-treated fiber was almost not affected by fiber stretching.

Removal of Zirconium (Zr) from Aqueous Solution by Polymer Enhanced Ultrafiltration

Although the world output of zirconium has been declining, increasing zirconium consumption cannot compete with this situation. For this reason, removal and recovery of zirconium become important. This work is focused on the removal of Zirconium (as ZrO22+) ions from an aqueous solution using polymer-enhanced ultrafiltration (PEUF) techniques with water-soluble Poly (sodium-p-styrene sulfonate, SSS) sorbent. The negatively charged sulfonic acid groups in the polymer interact with positively charged ZrO22+ cation thereby enabling the efficient removal of ZrO22+through ultrafiltration. The effect of polymer: zirconium mole ratio, initial solution pH, and the presence of interfering ions on the removal of zirconium was investigated. The obtained results demonstrated that ZrO22+ can be removed from the aqueous solution by the PEUF technique with more than 99% efficiency at pH ≥ 2 using polymer: Zr molar ratio of 5:1. The presence of interfering ions did not affect the percent removal of ZrO22+.