Solvent Extraction of Boric Acid: Comparison of Five Different Monohydric Alcohols and Equilibrium Modeling with Numerical Methods

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.

Advances in Technologies for Boron Removal from Water: A Comprehensive Review

“…The key aim of this method is to identify an extractant with a low toxicity and high selectivity. Reported extractants include 2-ethyl-1,3-hexanediol (EHD), 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylphenol (CTMP), 2,2,4-trimethyl-1,3-pentanediol (TMPD), 2-butyl-2-ethyl-l,3-propanediol (BEPD), N,N-bis(2,3-dihydroxypropyl) octadecylamine (BPO), 2-butyl-1-n-octanol, 2-ethylhexanol, and 1,3 diolic compounds [ 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 ]. Ayers et al (1981) [ 130 ] studied the extraction efficiency of boron with 2-ethyl-1,3-hexanediol (EHD) and 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylphenol (CTMP).…”

Liquid–liquid extraction of boron from continental brines by 2-butyl-1-octanol diluted in kerosene

“…17–20 Among them, liquid–liquid extraction is the most used technology in hydrometallurgy for the recovery of many metals including boron. 21,22 Alcohols 23–25 diluted in kerosene, 12 toluene, 26 chloroform, 19,25 benzene 27 or sulfonated kerosene 23,24,28,29 were extensively reported in the literature as extractants to recover boron from brines.…”

“… 11 Thus, boron extraction from brine could be a good alternative to ores as the exploitation of boron ores implies high energy consumption for crushing and grinding steps and the use of huge amounts of chemicals to leach ore concentrates. 12 Furthermore, the huge demand of lithium in the next decades due to the exponential increase of lithium-ion battery production for electric vehicles will be responsible for the co-extraction of a considerable amount of boron from brines, which should be valorised as co-product.…”

A promising modified polyvinyl chloride for adsorption of boron: Preparation, adsorption kinetics, isotherm, and thermodynamic studies

“…This suggests that a pH buffer is required to prevent ester hydrolysis in an acidic environment. It is common practice to classify boron extraction agents as either mono‐hydroxy alcohols (2‐butyl‐1‐n‐octanol), 22–24 di‐hydroxy alcohols (diols), 25,26 or phenols 27 . Alcohols with 8–12 carbon atoms, such as 2‐ethyl‐1,3‐hexanediol (EHD), 28 2‐butyl‐2‐ethyl‐1,3‐propanediol (BEPD), 29,30 and 2,2,4‐trimethyl‐1,3‐pentanediol, 31 have been shown to have excellent boron extraction efficiencies. …”