Extraction and/or recovery of chromium (Cr) and nickel (Ni) from textiles industry wastewater by membrane separation using polymer inclusion membranes (PIMs) based on polymer supports polyvinylidene fluoride (PVDF) and polyvinyl pyrrolidone (PVP), with Nitrilotriacetic acid (NTA) as extractive agent (EA). Furthermore, to quantify the PIMs performances, the macroscopic parameters such as the membrane permeability, P, and the initial flux, J 0 , and the microscopic parameters such as the association constant, Kass, and the apparent diffusion coefficient, D*, were determined based on the Fick's first law and the saturation law of the EA by the substrate (S). Also, to explain the substrate (S) (Cr or Ni) recovery process performed by the membrane, and to elucidate the mechanistic aspects, the activation parameters such as the energy Ea, the enthalpy ΔH ≠ and the entropy ΔS ≠ , were determined. The efficiency of different PIMs to recover Cr and Ni was compared. Respectively, the influence of temperature and pH on removal performance was investigated. The results showed that the macroscopic and microscopic parameters increased with increasing temperature and acidity medium. Similarly, the values of the activation parameters make it possible to explain the membrane performance and to elucidate the mechanism relating to the diffusion of the extracted substrates through this membrane.

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The processes for the extraction and removal of Cr(VI) ions using the polymer inclusion membranes (PIMs) that contained nitrilotriacetic acid (NTA) or tris(2-aminoethyl)amine (TAM) as the extractive agent were reported in this study. Each PIM was prepared and characterized using SEM and FTIR techniques to understand the correlation between its structure (morphology and composition) and its performance. The effects of several factors were studied. The parameters permeability, P, initial flux, J 0 , association constant, K ass , apparent diffusion coefficient, D*, and activation parameters (energy, E a , enthalpy, ΔH ‡ , and entropy, ΔS ‡ ) were determined and quantified using the kinetic and thermodynamic models. Therefore, we can affirm that the mechanisms of these oriented processes are governed kinetically rather than energetically. The extractive agent TAM (P = 35.26 × 10 −7 cm 2 •s −1 , D* = 11.5326 × 10 −5 cm 2 •s −1 , E a = 6.03 kJ mol −1 , and ΔH ‡ = 3.53 kJ mol −1 ) was determined to be better for the selective extraction process of Cr(VI) ions in comparison to its counterpart NTA (P = 22.49 × 10 −7 cm 2 •s −1 , D* = 9.58 × 10 −5 cm 2 •s −1 , E a = 7.12 kJ mol −1 , and ΔH ‡ = 7.12 kJ mol −1 ). Therefore, the membranes developed using the TAM agent were adopted further to conduct experiments related to the processes of selective extraction and removal of Cr(VI) ions from the mixtures containing industrial P3R dye. The results of these experiments were conclusive and indicated a total and selective separation of the Cr(VI) ions and the P3R dyes with the observance of a clear improvement in the P, J 0 , and D* parameters and better membrane performance.

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