The effects of structural changes of organophosphorus cationic exchangers on metal-distribution curves (extraction efficiency vs. pH) have been investigated for the recovery of cobalt(II), nickel(II) and manganese(II) from acidic chloride solutions. By using alkyl groups with different branching and hydrophobicity and by including oxygen atoms in the hydrophobic chains of the cationic exchangers, it has been shown that the change of the chemical structure in the hydrophobic chains plays an important role in the extraction behaviours and causes more specifically a shift of the extraction curves to higher or lower pH depending on pK_a values of extracting agents (evaluated by using QSPR calculations), distribution constants of metal–ligand complexes between organic and aqueous phases and the formation constant of the metal–ligand complexes. Based on the present results, interest in the new cationic exchangers synthesized in the present work for cobalt(II), nickel(II) and manganese(II) separation is also discussed.

The transport of p-nitrophenol (PNP) through an agitated bulk liquid membrane (ABLM) was investigated. A kinetic model of two consecutive irreversible first order reactions was applied in order to describe pertraction. The influence of PNP concentration in the feed solution, NaOH concentration in the stripping phase, and the type of solvent on the transport parameters (k′ _f , k′ _s , t _max, , J _max) was studied. To describe transport kinetics, the apparent mass transfer coefficient (k′ [cm/s]) as a parameter independent of volume and a membrane area was proposed. The results indicated that pertraction efficiency decreases in the series: benzene > toluene > p-xylene. In the investigated range of concentrations, the influence of the feed phase concentration (PNP) on pertraction efficiency is much higher than the stripping phase concentration (NaOH). It was also found that pertraction is controlled by PNP diffusion and sorption (extraction) at the feed/liquid membrane interface. The average value for the overall mass transfer coefficient is equal to 3.564(±0.047) × 10⁻⁴ cm/s which is characteristic for the studied system.