Separation and Purification Technology 22-23 (2001) 543 – 550 Behaviour of copper and silver in complexing medium in the course of nanofiltration on both mineral and organic membrane A. Chihani a , D.E. Akretche a, *, H. Kerdjoudj a , M. Persin b , J. Sarrazin b a Laboratoire de Valorisation des Minerais, Institut de Chimie, U.S.T.H.B, BP 32, El -Alia, 16111 Bab Ezzouar, Algiers, Algeria b LMPM, UMR 9987, ENSCM, 8 rue de l’Ecole Normale, F34033 Montpellier Cedex 1, France Abstract The recent development of new mineral and organomineral membranes induced an increasing interest in the nanofiltration process. Their better mechanical as well as chemical properties allow them to challenge widely commercialised organic membranes. In this work, the behaviour of both copper and silver in the course of nanofiltration is studied in presence of nitriloacetic acid (NTA) and sodium thiosulphate. Filtrations were performed using two different types of membrane: a mineral gamma alumina membrane with a point of zero charge equal to 8.2, and an organic membrane (MT34). Effects of the nature of ligand, pressure, pH and metal concentration were examined on each studied membrane. Filtrations on organic membrane showed that only the molecular weight can be considered as an preponderant parameter in relation with the rejection yield. On the other hand, based on both electric interaction and molecule size, the mineral amphoteric membrane allowed various possibilities of separation between the two metals according to the pH value. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Nanofiltration; Thiosulphate; NTA; Mineral membrane; Organic membrane www.elsevier.com/locate/seppur 1. Introduction Nanofiltration is a membrane process based on molecules separation by means of a pressure gra- dient. Due to the restrictions on molecular weight cut-off ranges (100 – 200) and the membranes av- erage pore diameter (2 nm), this process occurs in between reverse osmosis and ultrafiltration. Nanofiltration emerged as a promising technique in both retention of medium sized molecules such as inorganic salts [1–3] and treatment of indus- trial effluents [4]. Nanofiltration was also used both to obtain drinking water from wastewater [5,6] and viruses removal from water [7,8]. Re- cently, new development in membranes synthesis has enhanced the nanofiltration process by reduc- ing the membrane cost and lifetime. Organic poly- meric membranes with surface active groups improved fouling resistance against hydrophobic colloids, oils, proteins and other organics [9]. Organomineral composite membranes based on polysiloxanes or polyphosphazene polymer grafted on a mineral support were tested in * Corresponding author. Tel./fax: +213-2-247311. 1383-5866/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S1383-5866(00)00136-2