Extractant-impregnated organogel for capturing heavy metals from aqueous solutions

An organogel of dodecyl acrylate loaded with an metal extractant di-2-ethylhexyl phosphoric acid (D2EHPA) or ethylhexylphosphonic acid (EHPNA) was applied for sorption of Zn(II) and Cu(II) from their hydrochloric acid solutions. Equilibrium and kinetics of sorption have been studied using the organogel of various crosslink degrees. The mechanism of metal sorption for each metal–extractant system was similar to that of metal separation in liquid–liquid extraction. Mass transfer flux for the metal ion uptake was in the range of 1.0–4.0 × 10−6 mol/(m2 s), and was independent of the crosslink degree. Kinetics of metal sorption with the organogel was similar to liquid–liquid extraction and ion exchange resin under the condition of large excess amount of extractant in comparison with the metal ion in feed solution. The metal uptake process seems to be classified as film-diffusion controlled. More than 98% of the extractant was retained after repeating five times the sorption–desorption cycle. Substantially high percentage of metal ion sorption and desorption was achieved in the cyclic use of the organogel. The results suggested the feasibility of extractant-impregnated organogels for separating metal ions from their aqueous solutions.