Equilibrium and kinetic studies of the extraction of chelated copper(II) anions with Aliquat 336

Abstract

The equilibrium and kinetics of solvent extraction of Cu 2 from aqueous solutions containing equimolar EDTA with Aliquat 336 in n-decanol and kerosene at 298 K were investigated. The concentrations of Cu 2 (8±50 mol m), and Aliquat 336 (20±100 mol m À3 ) were varied. A semi-empirical model with three parameters was proposed to describe the equilibrium behavior, in which the non-idealities in both aqueous and organic phases were considered. Over the ranges studied, the model agreed reasonably well with the experimental data (standard deviation, 15%). The forward and backward reaction rate constants were determined as (5.31 AE 0.16)Â10 À6 m 9/4 mol À3/4 s À1 and (2.62 AE 0.09)Â10 À7 s À1, respectively, at 298 K. An interfacial reaction mechanism was proposed, which revealed that the reaction between the chelated anions and trimeric amine molecules at the interface was rate limiting. The derived rate laws were consistent with the experimental results.

Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by solvent extraction

“…In extraction experiments, equal volumes (50 cm 3 , each) of the organic and aqueous phases were placed in a 250-cm 3 glass-stoppered flask, and were agitated with a magnetic stirrer at 400 rpm for 24 h. Preliminary experiments had shown that the extraction reactions were complete within 12 h [10,11]. The temperature was controlled in the range 15-35 • C in water bath.…”

“…Under the conditions studied, the concentrations of Cl − and CuL 2− are low enough compared to extractant concentration so their activity coefficients are assumed to be kept constant [10,11]. Thus, the thermodynamic equilibrium constant can be expressed as follows by substituting Eqs.…”

“…The non-ideality of organic phase in reactive extraction systems is usually expressed in terms of ideal associated solution concept, i.e., aggregation of complexes [10,11,[14][15][16][17]. In extraction of HNO 3 with the nitrate salt of Aliquat 336, the non-ideal behavior of organic phase was considered assuming that the logarithm of activity coefficient ratio of the complex to extractant is proportional to extractant concentration [15].…”

“…They are operated in different devices although they have similar chemical principles [8]. Previous studies have shown that Cu(II) can be effectively co-extracted with EDTA or NTA in the form of the complexed anions from aqueous streams with quaternary amines such as Aliquat 336 (tri-n-octylmethylammonium chloride) [9][10][11]. Thus, the acceptable distribution ratio offers the possibility of using solvent extraction for removal of Cu(II) from such complexed solutions.…”