Journal of Membrane Science 248 (2005) 1–14 Comparative performance of non-dispersive solvent extraction using a single module and the integrated membrane process with two hollow fiber contactors Anil Kumar a,1 , R. Haddad a , F.J. Alguacil b , A.M. Sastre a,∗ a Department of Chemical Engineering, Universitat Polit` ecnica de Catalunya, ETSEIB, Av. Diagonal 647, E-8028 Barcelona, Spain b Centro Nacional de Investigaciones Metal´ urgicas (CSIC), Avda. Gregorio del Amo, 8 Ciudad Universitaria, E-28040 Madrid, Spain Received 12 November 2003; received in revised form 19 November 2003; accepted 9 September 2004 Available online 30 December 2004 Abstract Hollow fiber non-dispersive solvent extraction (HFNDSX) was carried out with one module (batch process) using (0.562 M) 18% LIX79/n- heptane by passing Ag(CN) 2 - alkaline feed through the tube side and organic extractant through the shell side in counter-current mode. Similarly, stripping was done by passing NaOH through the tube side and loaded organic through the shell side using the same module after washing (in batch operation). On the other hand, in the integrated membrane process (IMP), non-dispersive solvent extraction of silver cyanide and stripping of silver cyanide from organic complex were performed simultaneously using two hollow microporous hydrophobic polypropylene fiber contactors each for extraction and stripping, respectively. The overall mass transfer coefficient obtained in the integrated process was observed to be greater than the values of the mass transfer coefficient (K E Ag ) obtained with the single module (no stripping). The various hydrodynamic and chemical parameters, such as linear flow velocity of the feed aqueous phase (3.07 cm/s ≥ υ f ≥ 0.92 cm/s), linear flow velocity of the organic phase (1.18 cm/s ≥ υ f ≥ 0.39 cm/s), NaCN concentration in the feed, pH variation in the aqueous feed and NaOH concentration in the stripping phase, were optimized in the single module. Some selective experiments were performed with two modules in order to compare the performance of IMP with that of HFNDSX. The mass transfer coefficients were calculated under different hydrodynamic and chemical conditions with a single module, and rate-controlling steps in extraction and stripping were identified. Similarly, the mass transfer coefficients were evaluated using IMP and attempts were made to solve operational problems with HFNDSX using a single module in counter-current mode. © 2004 Elsevier B.V. All rights reserved. Keywords: Hollow fiber non-dispersive solvent extraction; Integrated membrane process; Hollow fiber contactors 1. Introduction Membrane science and technology has led to significant innovations in both processes and products over the past few decades, particularly with a view to sustainable industrial growth. Membrane technology using suitable fiber contac- ∗ Corresponding author. Tel.: +34 93 4015823; fax: +34 93 4015814. E-mail addresses: dranil@bom3.vsnl.net.in (A. Kumar), ana.maria.sastre@upc.es (A.M. Sastre). 1 On leave from PREFRE, Nuclear Recycle Group, Bhabha Atomic Re- search Centre, Tarapur 401502, Maharashtra, India. Fax: +91 2525 282158. tors has been demonstrated in a range of applications in fermentation, pharmaceuticals, waste water treatment, chi- ral separations, semiconductor manufacturing, carbonation of beverages, metal ion extraction, protein extraction, volatile organic compound (VOC) removal from waste gas, and os- motic distillation [1,2]. In the field of precious metal recovery, gold has been successfully separated from hydrometallurgi- cal alkaline cyanide solutions in the presence of other base metal salts using hollow fiber non-dispersive solvent extrac- tion (HFNDSX) [3]. Similarly, silver needs to be recovered from a variety of sources as this metal has gained greatly in importance owing to interest in its new technological ap- 0376-7388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2004.09.003