TRACE ION METHOD FOR TRACE-ION METHOD FOR TRACE-ION METHOD FOR CHARACTERIZATION OF NCHARACTERIZATION OF NCHARACTERIZATION OF N

Laia Llenas1, Xavier Martínez-Lladó1, Miquel Rovira1,Laia Llenas , Xavier Martínez Lladó , Miquel Rovira ,

1 Environmental Technology Area CTM Centre TecnològiEnvironmental Technology Area, CTM Centre Tecnològi

2 ICREA; 3Department of Chemical Engineering Polytech2 ICREA; 3Department of Chemical Engineering, Polytech

INTRODUCTION AND OBJECTIVESINTRODUCTION AND OBJECTIVESReal waters are usually complex mixtures of predominantly ionic solutes Modelling memReal waters are usually complex mixtures of predominantly ionic solutes. Modelling memproperties with respect to single ions In the properties obtainable from the measurementsproperties with respect to single ions. In the properties obtainable from the measurements

i “ t l d” d t th t l i i l t i fi ldanions are “entangled” due to the spontaneously arising electric fields.

The underlying observation of the approach of trace ions is that the effect of these fields onThe underlying observation of the approach of trace ions is that the effect of these fields oni l lt O th th h d h th t i t ti ffi i tl l thsingle salts. On the other hand, when the trace-ion concentrations are sufficiently low, the m

considered a kind of non-interfering probes for the studies of mechanisms of transfer of domg p

In [2] it was shown that the dependence of rejection of various single salts on the transIn [2], it was shown that the dependence of rejection of various single salts on the transMoreover, it was shown that this model can easily explain the experimentally observed highy p p y gcommonly used “nano-porous” model cannot Within the scope of solution-diffusion modelcommonly used nano porous model cannot. Within the scope of solution diffusion modelcoupling between the volume and solute transfers) This makes possible a very simple decoupling between the volume and solute transfers). This makes possible a very simple de

bt i i b t t ti f i t l d tobtaining membrane transport properties from experimental data.

The objective of this work is to generalize the solution-diffusion-model to include trace ionThe objective of this work is to generalize the solution-diffusion-model to include trace ionl fl i bt i d A d i l t d t l t th i t i i j ti t thvolume flow is obtained. A procedure is also presented to relate the intrinsic rejections to the

from the treatment of rejection of the dominant salt.j

DATA TREATMENT PROTOCOLDATA TREATMENT PROTOCOL

Treat the rejection of dominant salt by means of solution-diffusion-film model: obtain theea e ejec o o do a sa by ea s o so u o d us o ode ob a emembrane permeability to the salt and the thickness of unstirred layer.membrane permeability to the salt and the thickness of unstirred layer.

B i th ti t d l f ti d l thi k d lit t d t th By using the estimated value of unstirred layer thickness and literature data on thediff i ffi i t f i l l t th t ti f th d i t lt d thdiffusion coefficients of ions calculate the concentrations of the dominant salt and thet t th b f d th th i i t i i j titrace at the membrane surface and, thus, their intrinsic rejections.

Present the two-parameter equation for the intrinsic rejection of trace ions in special Present the two-parameter equation for the intrinsic rejection of trace ions in specialcoordinates where the plot has to be linear; fit one parameter to obtain a linearcoordinates where the plot has to be linear; fit one parameter to obtain a lineardependence and determine the other parameter from the slopedependence and determine the other parameter from the slope.

Estimate the membrane permeabilities to single ions by using thermodynamicp g y g yrelationships.e a o s ps

RESULTS AND DISCUSSIONRESULTS AND DISCUSSION

NF270 5000 ppm NaCl + 50 ppm CaCl2NF270, 5000 ppm NaCl + 50 ppm CaCl2

1

0 9

1

smP 61630 8

0.9 smPNa 6.1630 7

0.8Na, observable

PNa

6120 6

0.7

(-) Na, obs., model smPCl 6.12

0 5

0.6

ctio

n Na, intrinsic

N i t d l

smPCl 6.120.5

ejec Na., int., model

Ca observable smP 7780.4

on r Ca, observable

Ca intrinsic

smPCa 7.780.3

i Ca, intrinsic

Ca int model0.2

Ca, int., model

0.1

0

0 20 40 60 80 100 120 140 1.6

trans-membrane volume flow (m/s)y = 3E-07x2 + 0 7149x - 0 0013

1.4y = 3E-07x + 0.7149x - 0.0013

1.2

1

0 8

1

0 6

0.8

0.6

smPN Cl 423 373 0.4smPNaCl 4.23 37.30.2

smP 2108 71500

smP 2.108 715.00 0.5 1 1.5 2

CONCLUSIONSCONCLUSIONSCONCLUSIONS

In pressure-driven membrane processes, spontaneously arising electric fields cause cop essu e d e e b a e p ocesses, spo ta eous y a s g e ect c e ds cause cotrans-membrane flows of various ions.trans membrane flows of various ions.

These coupling phenomena can be mastered only if one knows the membrane transportp g p y pions (and not only to salts).( y )

Th ff t f t l i i l t i fi ld i ll i ibl i l t l t The effects of spontaneously arising electric fields are especially visible in electrolyte mlt d t i ( )salt and trace ion(s).

This can be exploited for the determination of membrane permeabilities with respect to sin This can be exploited for the determination of membrane permeabilities with respect to sin

REFERENCESREFERENCESREFERENCES

[1] A Yaroshchuk V Ribitsch J Membr Sci 201 (2002) 85 94[1]. A.Yaroshchuk, V.Ribitsch, J.Membr.Sci. 201 (2002) 85-94

[2]. A.Yaroshchuk, X.Martínez-Lladó, L.Llenas, M.Rovira, J.de Pablo, J.Flores, P.Rubio,[ ] a os c u , a e adó, e as, o a, J de ab o, J o es, ub o,Desalination and Water Treatment accepted for publication on 20/04/2009Desalination and Water Treatment, accepted for publication on 20/04/2009 .

THE ADVANCED THE ADVANCED THE ADVANCED NF MEMBRANESNF MEMBRANESNF MEMBRANES

Joan DePablo1,3, Andriy Yaroshchuk2,3Joan DePablo , Andriy Yaroshchuk

ic Av Bases de Manresa 1 08242 Manresa Spainic, Av. Bases de Manresa 1, 08242 Manresa, Spain

hnic University of Catalonia Av Diagonal 647 08028 Barcelona Spainhnic University of Catalonia, Av. Diagonal 647, 08028 Barcelona, Spain

mbrane performance in electrolyte mixtures requires the knowledge of membrane transportmbrane performance in electrolyte mixtures requires the knowledge of membrane transports of rejection of single salts the membrane transport properties with respect to cations ands of rejection of single salts, the membrane transport properties with respect to cations and

n the trans membrane transfer of traces is much more directly visible than in the rejection ofn the trans-membrane transfer of traces is much more directly visible than in the rejection ofb ti ff t d b th f t Th f th l tt bmembrane properties are unaffected by the presence of traces. Therefore, the latter can be

minant ions [1].[ ]

s membrane volume flow can be quite well described by the solution diffusion film models-membrane volume flow can be quite well described by the solution-diffusion-film model.rejections of sulfates from concentrated electrolyte solutions (seawater, brines) whereas thej y ( )the reflection coefficients of all solutes are considered to be equal to one (no convective, the reflection coefficients of all solutes are considered to be equal to one (no convective

scription of trans membrane solute transfer and the development of efficient procedures ofscription of trans-membrane solute transfer and the development of efficient procedures of

ns A very simple analytical formula for the intrinsic rejection of traces vs trans-membranens. A very simple analytical formula for the intrinsic rejection of traces vs. trans-membraneb bl b i i f ti th t t f t ti l i ti bt i ble observable ones by using information on the extent of concentration polarization obtainable

EQUATIONSEQUATIONSQ

11 obsm

s PRc 1exp1 s

obss

s PeRcsc

1m d

1

111exp1exp t obsZobsm

t dyRPeRPe

c

11111exp1exp

tZobstsstyR

RPeRPec

exp 11tPe st yRc

DD VJPe

tD

DDZZ

D δ - thickness of unstirred layer

DZDZV

ts DPe,

sD

DZDZDs δ - thickness of unstirred layer

DZDZ tsD , s DZDZ

PPZZ PP PsR

1

1 PP 1 Z

PPZZP

PP Z

PP s

1

s

R

11 st PP 1 tZ

PZPZPs

PZPZ Z1

st R

R

1ln

1

1ln

1

P permeability to the trace P permeabilities to the ions of dominant salt

Pt – permeability to the trace P± – permeabilities to the ions of dominant salt

NF270, 4750 ppm CaCl2 + 13 ppm NaCl

0 90.9

P 020.7Na intrinsic smPCa 0.2

0.5Na, intrinsic

Na, int., model

Ca

0 3

0.5

n (-

)

, ,

Na, observable smPCl 8.130.3

ctio

n

Ca, intrinsicsmPCl 8.13

0.1

reje

c

Ca, int., model smP 838-0.1io

n Na, obs.,outlyers

N i t tl

smPNa 8.380 3

Na, int., outlyers

Ca observable

0 5

-0.3 Ca, observable

-0.5

-0.7

0 20 40 60 80 100 120 0trans-membrane volume flow (m/s)

0

0 0.5 1 1.5 2 2.5 3 3.5-1

-22

-3

smPC Cl 7.4 -426.8smPCaCl 7.42

26.8

smP 72 y = 5E-07x2 - 1.6583x + 0.009-566.1smP 72 y 5E 07x 1.6583x 0.009-6

66.1

onsiderable coupling between thePermeability Dominant Dominant

o s de ab e coup g bet ee t ePermeability Dominant Dominant

(m/s) NaCl CaCl2t properties with respect to single (m/s) 2

P 163 6 38 8

p p p g

PNa 163.6 38.8i t i ti f d i t PC 78 7 2 0mixtures consisting of a dominant PCa 78.7 2.0

P 12 6 13 8PCl 12.6 13.8ngle ionsngle ions.

ACKNOWLEDGEMENTSACKNOWLEDGEMENTSACKNOWLEDGEMENTS

This study was financially supported by Sociedad General de Aguas deThis study was financially supported by Sociedad General de Aguas deB l (AGBAR) ithi th f CENIT j t “D llBarcelona (AGBAR) within the scope of CENIT project “Desarrollostecnológicos hacia un ciclo del agua urbano auto-sostenibleg g(SOSTAQUA)”(SOSTAQUA) .