Use of montmorillonite to recover carboxylic acids from aqueous medium

Abstract

In this work, it was investigated the use of montmorillonite as a trap to recover small carboxylic acids from aqueous medium. TOC and titration analyses showed remarkable uptake of organic acid molecules, e.g. 46, 49, 9 and 16 mmol g−1 of acetic, propionic, citric and lactic acids, respectively (1.4–3.6 gacid gclay−1), in concentrations up to 4 mol L−1. XRD, TG-MS and BET indicated that acetic and propionic acids can be easily recovered from montmorillonite, producing some delamination of the clay mineral with the formation of mesopores and increasing the specific surface area to 83 m2 g−1. Non-volatile citric and lactic acids are also efficiently removed from aqueous solution. Although the uptake mechanism of the acids by the clay is not clear, XRD and FTIR results indicate a possible intercalation process that strongly affects the Si[sbnd]O tetrahedral layer of Mt. Preliminary experiments using a strongly acidic aqueous fraction of bio-oil indicated that montmorillonite can be used to recover small organic acids from the complex mixture by selectively trapping.