Synthesis and bharacterization of poly(vinyl alcohol)-boric acid beads from PVA with several hydrolysis degrees

Abstract

This work describes the synthesis and characterization of polyvinyl alcohol)-boric acid (PVA-BA) sphere-like beads. The PVA-BA beads were prepared by the dropwise addition of PVA aqueous solutions to a boric acid solution under constant stirring and controlled temperature. Different temperatures for bead formation as well as PVA with several hydrolysis degrees were used and tested. PVA with several hydrolysis degrees were characterized regarding molecular mass and intrinsic viscosity, while characterization of PVA-BA beads was carried out using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results obtained with TGA have shown that structural changes occurs in PVA following the reaction with boric acid and that the spheres formed are thermally stable, whereas SEM analysis demonstrated that symmetric sphere-like beads were formed, with considerable porosity, which are requisite for solid supports when applied to effluent treatment. Trace element extraction tests were carried out using inductively coupled plasma mass spectrometry (ICP-MS). Without the addition of a chelating agent, no significant extraction occurred from acidic solutions, while after the addition of ethylenediaminetetracetate, less than 10% of the trace element content was extracted from the aqueous phase by the PVA-BA beads. However, after the addition of ammonium O,O-diethyldithiophosphate (DDTP), over 10% of As, Co, Cr, Fe, Sr and Zn, 40% of Cd and 70% of Pb were extracted from acidic solutions, even without any further optimization. The results have shown that the synthesized PVA-BA beads are potential alternatives for trace element extraction in effluent treatment.