Solvent extraction of boron with 2-ethyl-1,3-hexanediol and 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylol-phenol

The solvent extraction equilibrium of boron extraction has been studied for petroleum ether solutions of 2-ethyl-1,3-hexanediol (EHD) and 2-chloro-4-(1,1,3,3-tetramethylbutyl)-6-methylol-phenol (CTMP), employed both singly and in admixture. Theoretical considerations are developed to account semi-quantitatively for observed trends in extraction with changes in pH and organic reagent concentration. The mixed reagents in a 1 : 1 concentration ratio give a much enhanced extraction in the pH range 8–12 and extraction becomes essentially pH independent when the EHD/CTMP ratio is 3 : 1. Boron extraction is largely unaffected by changes in the type of cation present (Na⁺, Ca²⁺ or Mg²⁺). These observations are interpreted in terms of the opposing pH dependences of the two reagents and of the formation of different mixed complexes in the organic phase. The possible application of mixed-reagent solvent extraction is discussed in terms of boron pollution control.