Modification of the AMX membrane surface by polyethyleneimine: Effect of ionic strength on the membrane ion exchange selectivity

• Published in: Canadian journal of chemical engineering 2016-12, Vol.94 (12), p.2386-2393
• Main Authors: Louati, Islem, Guesmi, Fatma, Hannachi, Chiraz, Hamrouni, Béchir
• Format: Article
• Language: English
• Subjects: adsorption models; AMX membrane; Ion exchange; ion exchange selectivity coefficient; ionic strength; Mathematical models; Membranes; Polyetherimides; Polyethyleneimine; Selectivity; Strength; Surface chemistry
• ISSN: 0008-4034; 1939-019X
• DOI: 10.1002/cjce.22615

In order to improve the selectivity of the AMX membrane, a polyethyleneimine (PEI) layer was adsorbed on its surface by the immersion of the considered membrane in a solution of PEI. The adsorption process of PEI was studied and the results were well correlated with the Langmuir model and with Lagergren's pseudo‐first‐order kinetic model. Equilibrium ion exchange isotherms of (Cl−/NO3−), (Cl−/SO42−), and (NO3−/SO42−) systems, using modified AMX membrane, were established at various ionic strengths from 0.1 to 0.5 mol/L and at constant temperature of 298 K. The results obtained with the modified membrane, in this range of ionic strengths, showed that the affinity order was: NO3−>Cl−>SO42− at I = 0.1 mol/L and I = 0.2 mol/L and it was Cl−>NO3−>SO42− for I = 0.3 mol/L and I = 0.5 mol/L. The ion exchange selectivity coefficients KAB, thermodynamic ion exchange equilibrium constants KA°B, and the standard free enthalpies ΔrG° of the ion exchange reactions were determined for the three binary systems. These results were compared with those obtained with the unmodified membrane. It was observed that for the modified membrane the ion exchange selectivity towards sulphate ions decreased and increased towards monovalent anions.