Abstract
Solvent extraction is one of the common methods for the recovery of boric acid (or boron) from aqueous solutions. A wide variety of different compounds including monohydric alcohols has been tested, and there is wide recognition that they are rather ineffective compared to other extractants such as diols. Nevertheless, monohydric alcohols find application in industrial processes, demonstrating their efficiency. The intention of this study is to clarify this discrepancy and to provide an overall picture of monohydric alcohols as an extractant for boric acid. Five different monohydric alcohols are the object of this study: n-octanol, 2-ethyl-1-hexanol, 2-butyl-1-octanol, 2-octanol and 3,7-dimethyl-3-octanol. A special focus of this work is the examination of the effect of the structure of the carbon chain and the effect of the composition of the aqueous phase on the extraction efficiency. As well as the extraction efficiency for boric acid, other important properties are examined such as the viscosity of the organic phase, the solubility of alcohols in the aqueous phase and the co-extraction of salts used as a salting-out agent (NaCl, Na2SO4, MgCl2, LiCl, LiNO3). Finally, a numerical algorithm is developed to calculate the relationship between the number of theoretical stages and the phase ratio at equilibrium for selected extraction systems.
Highlights
Boric acid is produced industrially from borate minerals and brines [1]
As well as the extraction efficiency for boric acid, other important properties are examined such as the viscosity of the organic phase, the solubility of alcohols in the aqueous phase and the co-extraction of salts used as a salting-out agent (NaCl, Na2 SO4, MgCl2, LiCl, LiNO3 )
This study investigates the solvent extraction of boric acid with monohydric alcohols in detail
Summary
Boric acid is produced industrially from borate minerals and brines [1]. The majority of boric acid is obtained from minerals such as borax (Na2 [B4 O5 (OH)4 ]·8H2 O), kerinte (Na2 B4 O6 (OH)2 ·3H2 O) colemanite (Ca[B3 O4 (OH)3 ]·H2 O) and howlite (Ca2 B5 SiO9 (OH)5 ).Borax became by far the most important mineral for the borate industry by the end of the20th century [2]. Boric acid is produced industrially from borate minerals and brines [1]. The majority of boric acid is obtained from minerals such as borax (Na2 [B4 O5 (OH)4 ]·8H2 O), kerinte (Na2 B4 O6 (OH)2 ·3H2 O) colemanite (Ca[B3 O4 (OH)3 ]·H2 O) and howlite (Ca2 B5 SiO9 (OH) ). Borax became by far the most important mineral for the borate industry by the end of the. The production process from high-grade borax concentrates or other alkali borates consists of dissolving borates in mineral or organic acids (HX) (Equation (1)) and the subsequent crystallization of boric acid and sodium salt (NaX) as a by-product. Na2 [B4 O5 (OH)4 ] · 8 H2 O + 2 HX −−→ 4 H3 BO3 + 2 NaX + 5 H2 O In the process, sulfuric acid is preferred [3]; techniques based on nitric acid [4], oxalic acid [5] and propionic acid [6] have been described.
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