Stepwise Recovery of Molybdenum, Vanadium, and Tungsten with Amino-Type “Trident” Molecule by Stripping

Abstract

ABSTRACT The long-chain tripodal amino reagent 1,1,1-tris(aminomethyl)nonane was prepared and used to extract various metal species. The results were compared with the results of extractions using the related long-chain primary decylamine. The study was focused on the extraction of the oxyanions of V(IV), Mo(VI), and W(VI). Factors affecting the extraction efficiency were the shaking time, pH, and diluent. The oxyanion species distributions particularly strongly affected the oxyanion extraction efficiencies. The tripodal amino reagent extracted Mo(VI) with a good degree of specificity at pH 5–6, and the amount of Mo(VI) extracted increased until 12–14 min had passed but then decreased. The relationship between the amount of Mo(VI) extracted, the potential, and the pH suggested that a heptanuclear Mo(VI) species was extracted by the protonated tripodal amino reagent until 12–14 min had elapsed. The data further suggested that the change in pH at that point caused the heptanuclear Mo(VI) species to be converted into a mononuclear species because of protonation of the amino reagent, meaning the extracted Mo(VI) then started to be released back into the solution. The Mo(VI) extraction sequence did not include any redox reactions. From the experimental results, a stepwise method for stripping the metals from the organic phase was developed to recover molybdenum, tungsten, and vanadium. Multiple protonation of the tripodal amino reagent at different pK a values was taken into account as a “structural effect” of the tripodal compound.