Liquid Extraction of Inorganic Acids with α-Aminophosphoryl Compounds

Abstract

Liquid extraction of inorganic acids, such as hydrochloric, hydrobromic, hydroiodic, and nitric, with four =-aminophosphonates with different-size hydrocarbon substituents in the aminomethylphosphoryl skeleton was studied. The extraction effectiveness increases with increasing number of carbon atoms in the molecules of organophosphorus extractants, that is with increase in their lipophilicity, and is also affected by the hydration enthalpy of the inorganic acid anion. The extractive ability of phosphorylated amines is 3!4 orders of magnitude lower compared with corresponding amines, on account of the fact that the basicity of the former is decreased by the electron-acceptor phosphoryl group. The absence of satisfactory linear two-and three-parameter correlations between the extraction constants and the number of carbon atoms in and the basicity of phosphorylated amines is evidently connected with the disregard for other structural and medium factors that may influence the extraction coefficients.We previously found that a-aminophosphonates are capable of extracting ions of noble metals, such as gold, platinum, and palladium, as well as ions of other metals that accompany noble metals in natural and technological objects [1,2]. Metal ions are most commonly extracted into organic phase from aqueous solutions of wide-range acidity, and the effectiveness of separation of extracted mixtures is much dependent on the ability of extractants to transport corresponding inorganic acids together with target substrates. The ability of a-aminophosphonates to transport inorganic acids through hydrophobic impregnated membranes we studied in one of our previous works [3].

Synthesis of β-Aminophosphonates and Study of Their Acid-Base Properties and Phase Distribution in Water-Organic Solvent Systems

“…Apart from high efficiency as bioactive substances, -aminophosphoryl compounds were shown to be capable of forming complexes with various species, including metal ions, organic and inorganic acids, etc. [4,5]. In particular, we studied -aminophosphonates as extractants which ensured selective separation of noble metal ions from concomitant elements [6].…”