Spectroscopic and Computational Analyses of Liquid–Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes

Abstract

Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid–liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extractant, which takes place at the liquid–liquid interface experimentally and theoretically. Raman spectroscopy for the microflow reactor provided the concentration of boric acid after extraction, whereas density functional theory calculation showed the reaction energy profiles of the underlying chemical reactions. Calculation results suggested that H2O molecules from the aqueous phase promote extraction by enabling the formation of [BOH-HOH-HOC], a sufficiently stable, nonsteric structure, which stabilizes the transi...