NAMS 2002 Workshop - ICOM 2008

Facilitated Transport Membranes – 2
Friday July 18, 10:15 AM-10:45 AM, Wai’anae
Explorative Investigation of Cu(II) Facilitated Transportation Through
Supported Liquid Membrane and Its Derivatively Successful Story
Q. Yang (Speaker), National University of Singapore, Singapore
T. Chung, National University of Singapore, Singapore - chencts@nus.edu.sg
J. Jiang, National University of Singapore, Singapore
N. Kocherginsky, National University of Singapore, Singapore
The initiative for this work is to develop a novel and more efficient supported
liquid membrane (SLM) based process to recover copper and regenerate spent
ammoniacal etchant solution with low operation cost and without generating
secondary waste for Printed Circuit Board (PCB) manufacturers. A
comprehensive study has been conducted in this work including 1) the quantum
chemical computations for selecting proper carrier for Cu(II) extraction in SLM
system; 2) the fundamental kinetics and mechanism of Cu(II) transport through
SLM system; 3) a successful lab-scale to pilot-scale spent etchant treatment
process.
First of all, a comparative study of two widely used Cu(II) extractants, namely
LIX54 and LIX84, and their impregnated SLM systems was carried out in this
work. Experimental and computational characterizations of LIX54/Cu(II) and
LIX84/Cu(II) complexes were investigated and the results agreed well in the
reaction mechanisms, complexes geometries and Cu(II) extraction strengths of
these two carriers. Cu(II) transmembrane fluxes at different conditions were
compared and the results showed that LIX54 had slightly higher copper removal
rate in the ammoniacal solution but much poorer copper loading in acidic media.
Much higher selective separation performances of Cu(II) over Zn(II) and Cd(II)
and no ammonia carry-over provide LIX54 significant advantages over LIX84 for
ammoniacal solutions treatment.
Subsequently, Cu(II) recovery from industrial ammoniacal wastewater using flat
sheet SLM system was investigated. LIX54 in kerosene was used as a carrier in
the liquid membrane phase to extract and transfer copper. Detailed theoretical
model for facilitated transport through flat membrane was developed, where
diffusion of copper complex with ammonia in aqueous stagnant layer and fast
reactions of the carrier and copper species in aqueous reaction layer have been
taken into account. This model, where the carrier moves slightly out from the
membrane in the reaction layer, then transfers from one aqueous phase to
another through the membrane, and finally moves back, is called Big Carrousel.
Mathematical model simulation demonstrated that only Big Carrousel model,
based on the ability of the carrier to leave the membrane and to react with copper