SORPTION OF BORIC ACID USING POLYCONDENSATION ANION EXCHANGERS

Abstract

The article presents the results of a study the influence of such factors as pH, temperature, and boric acid concentration on the boron sorption behavior in model aqueous solutions under static conditions by various forms of polycondensation anion exchangers based on monoethanolamine and epichlorohydrin (SB-1) and pyrocatechol and formaldehyde (SB-7). The hydroxyl-form polycondensation anion exchangers, as well as polymerization ones, have a higher sorption activity and selectivity for boron compared to anion exchangers in the boron salt forms, while SB-1 anion exchanger containing aminooxyethyl functional groups possesses the highest sorption activity and selectivity to boron. The established relationships and results of kinetic and IR spectroscopic studies have revealed that the sorption of boric acid by SB-1 anion exchanger is carried out by two complementary mechanisms. They are: 1) chemisorption of boric acid by OH groups of the anion exchanger, accompanied by the formation of the mononuclear borate anion exchanger, [B(OH4)]−, followed by the formation of polynuclear forms of boron, [B4O5(OH)4]2− in the sorbent phase and 2) complex formation of tetraborate anions with the nitrogen atom in aminooxyethyl groups. This fact explains occurring super-equivalent sorption of boron from boric solutions at a concentration more than 0.057 M and pH 5.0–7.5. © 2021. All Rights Reserved.