Fidelity of Al2(SO4)3 for the Discharge of Pectin during the Pretreatment of Apocynum Venetum

Abstract

During the extraction of fibers from the bast of A. venetum, there is an issue of the existence of undesirable macromolecules, for example, pectins. Separation of these compounds is mostly done by pretreatment with H2SO4 and then by NaOH boiling in the traditional method (Fiber-C). The use of Sulfuric acid for pretreatment may cause harm to both fibers and the environment. In order to overcome these limitations, attempts were made to find a new pretreatment (Fiber-N) method. The hypothetical premise of the new pretreatment strategy dependent on the use of Al2(SO4)3 is presented. Four model solutions were investigated using a method of measuring zeta potential. Furthermore, fibers obtained by pretreatment methods along with the raw fibers of A. venetum had been characterized by Electron spin resonance spectroscopy (ESR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and water retention value (WRV). Results showed that pure salts of Al2(SO4)3 presented improved binding properties with the pectin and causes better swelling and eventually helps to remove pectin than other pretreatment processes. Ultimately, Donnan equilibrium, metal ion complex formation, and Gouy–Chapman–Stern (GCS) model were used to theoretically elucidate the discharging mechanism of pectin macromolecules from A. venetum in the presence of Al3+ ions during pretreatment.

Keywords

• pretreatment
• pectin
• ion exchange
• ion binding
• swelling