XVII-th ARS SEPARATORIA – Borówno, Poland 2002
ACTIVE TRANSPORT AND SEPARATION OF Zn(II) AND Cu(II)
BY POLY(OXYPROPYLENE) BISPHOSPHATES AS
MACROIONOPHORES IN HYBRID LIQUID
MEMBRANE SYSTEMS
Romuald WÓDZKI and Marek ŚWIĄTKOWSKI
Nicholas Copernicus University, Faculty of Chemistry
87-100 Toruń, 7 Gagarina St., Poland
e-mail: [email protected]
Poly(oxypropylene) bisphosphates (POPBPs) have been synthesised by
the modification of polypropylene glycols (PPG 400, 1200, 2000) and used
as macroionophores of metal cations in a multimembrane hybrid system
comprising a flowing liquid membrane unit, cation exchange, and
pervaporation polymer membranes - MHS[FLM-PV] (scheme below).
Striping
solution
I
CEM
Feeding
solution
Striping
solution
CEM
Flowing LM
Feeding
solution
CEM
II pervaporation
I
Flowing LM
II
Low
pressure
PV
Flowing LM
Low
pressure
removal of water
Fig. Scheme of the MHS-FLM (I) coupled with the pervaporation process (II): MHS[FLMPV]; PV – pervaporation membrane, CEM – cation exchange membrane, LM –liquid
membrane
The ability of POPBPs to mediate the pertraction of some cations from a
mixture containing alkali (K+, Na+), alkaline earth (Ca2+, Mg2+) and transient
metal cations (Zn2+, Cu2+) has been studied and compared with the properties
of respective PPGs. POPBPs, after dissolving in 1,2-dichloroethane (liquid
membrane phase), have been observed to transport and separate cations in
the following order: Zn2+>Cu2+>>Ca2+, Mg2+, K+, Na+. An increase in the
molecular mass of POP chain changes the position of K+ cations in the order
from Zn2+>Cu2+>K+≥Na+,Ca2+>Mg2+ to Zn+,K+>Na+>Ca2+>Cu2+,Mg2+ as
observed for PPG400 and PPG2000, respectively. High ionic fluxes and
separation properties of POPBs depend mainly on the presence of ionisable
phosphoric acid end-groups. These groups, in cooperation with
poly(oxypropylene) chains, mediate the proton-coupled transport of cations
(counter-transport) leading to the effective up-hill transport of Zn2+ cations.
It has been found that the pertraction process assisted by the continuous
pervaporation of water from a liquid membrane results in stable functioning
and high selectivity of the system with POPBPs as the ionic carriers.
XVII-th ARS SEPARATORIA – Borówno, Poland 2002