Water Research 38 (2004) 593–600

ARTICLE IN PRESS

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0984-496-655.

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doi:10.1016/j.w

Metal ions removal from wastewater or washing water fromcontaminated soil by ultrafiltration–complexation

Raffaele Molinari*, Saverio Gallo, Pietro Argurio

Department of Chemical and Materials Engineering, University of Calabria, Via P. Bucci, Cubo 45/A, Rende (CS) I-87030, Italy

Received 18 September 2002; received in revised form 10 September 2003; accepted 14 October 2003

Abstract

In the present paper a process for removal of ions from wastewater or from washing water of contaminated soil by

using the weakly basic water-soluble polymer polyethylenimine (PEI) as chelating agent and the Cu2+ ion as model in

combination with an ultrafiltration process was investigated. The complexing agent was preliminarily tested to establish

the best operative conditions of the process. Next, ultrafiltration tests by using five different membranes were realised to

check membrane performance like flux and rejection. Finally, the possibility for recovering and recycling the polymer

was tested in order to obtain an economically sustainable process. Obtained results showed that complexation

conditions depends on pH: indeed, at a pH>6 PEI–Cu2+ complexes are formed, while at pHo3 the decomplexation

reaction takes place. Saturation condition is 0.333mg Cu2+/mg PEI, meaning a ratio PEI/Cu2+=3 (w/w). UF tests

showed good results using the PAN 40kDa membrane reaching an average copper concentration in the permeate of

2mg/l and a flux of 135.4 and 156.5 l/h.m2 at 2 and 4 bar, respectively. Metal rejection, permeate flow rate, and

possibility to regenerating and recycling the polymer makes the polymer-assisted ultrafiltration process (PAUF) very

interesting for metal ion removal from waters.

r 2003 Elsevier Ltd. All rights reserved.

Keywords: Ultrafiltration–complexation; Polymer-assisted ultrafiltration; Cu (II) ion removal from water; Wastewater treatment; Soil

remediation

1. Introduction

Water treatment plays an important role in the wide

subject of pollution problems solving and represents

today one of the most important fields of study. In fact,

a ‘‘rational hydrologic resource management’’ is neces-

sary because of increased world’s demand of water,

particularly in these last years owing to lacking of this

resource. Other than in the Mediterranean Middle-East,

it is known that in some regions of Southern Italy the

service of water distribution is not continuous, and this

phenomenon is happening also in Northern Italy

because of anomalous climatic changes, especially in

ing author. Tel.: +39-0984-496-699; fax: +39-

ess: r.molinari@unical.it (R. Molinari).

e front matter r 2003 Elsevier Ltd. All rights reserve

atres.2003.10.024

winter. In this situation some textile industries of

Northern Italy, which request big water consumption,

have taken into account to review their operational

system, treating and recycling wastewater, in order to

find a remedy for unoptimistic prevision for the future.

So, the approach of a pondered water consumption and

its purification and recycling has become very important

as stated also by the European Commission (Council

Directive 96/61/EC) for achieving integrated prevention

and control of pollution through the application of Best

Available Techniques (BAT) to obtain a high level of

protection of the environment as a whole.

The engineered systems associated with wastewater

reclamation, recycling and reuse can play an important

role in the natural hydrologic cycle. An overview of

the cycling of water from surface and ground-

water resources to water treatment facilities, irrigation,

d.

ARTICLE IN PRESSR. Molinari et al. / Water Research 38 (2004) 593–600594

municipal, and industrial applications, and to waste-

water reclamation and reuse facilities is described

elsewhere [1]. This scheme takes into account that in

most cases the reuse of wastewater can produce water

for non-potable applications.

Metal contamination is a dangerous cause of water

pollution: indeed, e.g., Cu2+ ions are essential nutrients,

but when people are exposed to Cu levels of above

1.3mg/l for short period of time, stomach and intestinal

problems occur. Long-term exposure to Cu2+ leads to

kidney and liver damage.

Separation processes for metal ions removal from

aqueous solutions are a major industrial activity cover-

ing processes ranging from production of potable water,

to leaching and recovery of metals from contaminated

soil or from ores, to detoxification of process water and

wastewater, also for water recycling and reuse. A variety

of separation processes for metal ions have been

developed up-to-date for industrial need: e.g., in water

softening (Mg2+, Ca2+ removal) the first studied

traditional process is the lime-soda method, which

causes a precipitation of hardness [2]. This technique,

like the others, consisting practically in an induced

sedimentation, produce water within international

health standards, but has two important drawbacks:

they produce big amount of sludge [3–5] containing

residual of reagents used, which result in a pollution

problem, and treated water may contain residual

coagulants if the process is not correctly controlled or

operated [6]. Another important method for metal

removal from polluted water is the ion exchange process,

which produces water within international quality

standards, but it is not a continuous process, because

of regeneration necessity [2].

Membrane processes play today an important role in

the field of wastewater purification and reuse. This well

consolidated technology is very interesting because of

low operative costs, conceptual simplicity, modularity,

and optimal quality of treated water. Furthermore, the

use of new materials permits to obtain very resistant

membranes, both on chemical and mechanical point of

view, for various applications [6–8].

For separating species with ionic dimensions, reverse

osmosis membranes are required but they will result in

high operative costs, low permeate flow rate and low

ions selectivity. In order to overcome these problems,

the ultrafiltration–complexation, also named polymer-

assisted ultrafiltration (PAUF), was introduced. Ultra-

filtration can be used for removal of trace metals from

aqueous streams, provided that these metals are

primarily bound to water-soluble polymers [9]. The

unbound metals pass through the membrane, whereas

the polymers and their complexes are retained. This

PAUF process can be applied for various purposes

such as the treatment of waste effluents, groundwater

and seawater. The advantages of this method are the

low-energy requirements involved in the ultrafiltration

and the high removal efficiency because of effective

binding [10]. Several research efforts have been carried

out to study the applicability of PAUF in metal removal

from water of various origins. Pivot of the study are the

consideration on technical and economical feasibility, to

respect the limits fixed by pollution laws: Juang and

Shiau [10] studied the metal removal from aqueous

solutions using chitosan-enhanced membrane filtration,

and in other two works [11,12] the authors considered

the problem of technical feasibility on the use of PAUF

for brackish water softening, or wastewater treatment by

using three weakly basic, water-soluble polymers like

chitosan, polyethylenimine (PEI), poly(diallyl dimethy-

lammonium chloride) to remove ions like Ca2+, Mg2+,

Na+, K+, Cu2+ and Zn2+. Tabatabai et al. [13] studied

the feasibility of PAUF for water softening in the

removal of Ca2+ and Mg2+ ions from hard water by

using the polymer sodium polystyrene sulfonate (PSS).

They demonstrated (with some economical considera-

tions) that the PSS needs to be recovered from the

retentate and regenerated appropriately, to be reused.

Steenkamp et al. [14] considered the Copper (II) removal

from polluted water with alumina/chitosan composite

membrane, giving attention prevalently to the problems

related to the synthesis of their composite support

and to the factors which influence metal removal

efficiency, like pore radii variation with temperature

and powder mixtures used, and chitosan coating

thickness. Vieira et al. [15] studied an application of

PAUF in metal removal from pulp and paper industry

wastewater.

All the cited works consider the PAUF and its

applicability in metal removal from water, but they use

polymers that in their complexing action to complex

ions of interest, release other ions, like Na+ or H+,

which results in a potentially modification of water

characteristic, or they do not consider the use of the

polymers at their maximum complexation ability,

saturation conditions and chemistry of polymer–metal

complexation.

In the present work, some results of a study on

metallic ions removal from wastewater and from

washing water of contaminated soils by means of PAUF

are reported.

The determination of complexation, de-complexation

and chemical conditions of saturation are discussed; the

results of ultrafiltration tests on five different mem-

branes realised by using the weakly basic poly(ethyleni-

mine) as the selective polymer and the copper as model

ion are reported. This polymer has the advantage of no

release of other ions in treated water because it does not

work by means of ionic exchange reaction, but it

complexes also counter-ions to form neutral complexes.

A criterion to find the membrane with the best

performance is also reported.

ARTICLE IN PRESSR. Molinari et al. / Water Research 38 (2004) 593–600 595

2. Materials and methods

Copper sulphate penta-hydrate (CuSO4 � 5H2O) from

Fluka Chemika (purity>99%) was used for preparing

Cu2+ solutions. Poly(ethylenimine) 50%wt solution in

water from Sigma-Aldrich (MW 10,000 and 60,000) was

the polymer utilised. Other chemicals used were H2SO4

(purity 95–97%) purchased by Riedel de Haen and

NaOH (purity>99%) from Merck.

The used ultrafiltration plant (Fig. 1) permitted to test

simultaneously five different UF membranes. It was

constituted by three sections: electric panel, to control

plant working; alimentation section, constituted by

a feed reservoir of 25 l, in which a cooling coil

was immersed with a thermostat and a level control

sound; ultrafiltration section, with a centrifugal pump

LOWARA CKM 70/34 that generates the flow (max

flow rate=1.5m3/h; max pressure=4.5 bar), five steel

plane cells (useful membrane surface area 14.18 cm2)

equipped with manometers and flow meters to control

operative transmembrane pressures and tangential flow

rates of the concentrate (retentate).

The thermostatic system controlled the operative

temperature, resulting isothermal ultrafiltration runs

(t ¼ 25�C). The coolant was simply tap water.

Before each ultrafiltration run the membranes were

characterised with demineralised water in the same

plant, in order to evaluate the relative membrane

permeability and the membrane fouling after the

ultrafiltration runs. During this characterisation, opera-

tive transmembrane pressure was fixed first at 4 bar to

stabilise the compaction, and later it was decreased

to 2 bar. Ultrafiltration tests were carried out setting

the operative pressure first at 2 bar and after increased

at 4 bar, because it is known that fouling tendency

Feed reservoir

PumpF

Permeateheader

Retentateheader

Fig. 1. Flowsheet of the ultrafiltration laboratory plant

increases with transmembrane pressure. The plant

was operated in batch mode recycling the five permeates

to feed reservoir. Every 30min (starting by the

time t ¼ 0min) permeates were collected for 2min

and their volumes measured in order to calculate

instantaneous flux; they were also analysed to determine

copper concentration. Each ultrafiltration run was

stopped (or pressure was changed) when steady state

was reached, that means permeate flux and copper

concentration were practically constant. The aver-

age time to reach the steady state was between 2.5

and 3 h.

Permeates collected in the steady-state condition were

also submitted to total organic carbon (TOC) measure-

ments, in order to verify if the polymer passed through

the membranes. The thermostat LT 100-1, the photo-

meter LASA 100 and the analytical kits LCK 380 and

LCK 381 (depending on the concentration of the total

carbon estimated in the sample) from Dr. Lange, were

used for carrying out TOC measurements.

Five different UF membranes were tested measuring

retention and water permeate flux. Some of their

characteristics are reported in Table 1 where fluxes

measured with distilled water at 2 and 4 bar are also

reported. The retention RTC; for the target component(TC), was measured by using its definition:

RTC ¼ 1� ½CTC;P=CTC;F�;

where CTC;P and CTC;F are the concentrations of the TC

(Cu2+) in the permeate and in the feed solution,

respectively.

The other important parameter, the volume permeate

flux (J), generally expressed as the volume obtained per

unit time (t) and per unit of membrane surface (S), was

low meters Plane cells

Feedheader

Permeates

able to tests simultaneously five UF membranes.

ARTICLE IN PRESS

Table 1

Some characteristics of the tested UF membranes

Membrane type Material Cut-off (kDa) Producer Water flux (l=h m2) (2–4 bar)

Iris 10 Polyether sulphone (PES) 10 Tech-Sep 33.85–55.00

FS 40 PP Fluoride-polypropylene 40 Dow 220.0–397.7

GR 40 PP Polysulphone-polypropylene 40 Dow 220.0–444.3

Iris 30 Polyether sulphone (PES) 30 Tech-Sep 114.2–207.3

PAN 40 Polyacrylonitrile 40 Tech-Sep 291.1–528.9

Fig. 2. Idealised structure of the polymeric complex PEI–

copper (II) ions.

R. Molinari et al. / Water Research 38 (2004) 593–600596

measured by the following equation:

J ¼ V=ðtSÞ:

Determination of copper concentration was carried

out by using an analytical kit (Carlo Erba Reagenti),

based on a colorimetric reaction and absorbance reading

at a 600 nm wavelength. Absorbance reading was

performed by using a Recording Spectrophotometer

UV–Visible 160A (Shimadzu Corporation-Analytical

instruments division).

A pH meter (Orion Research Incorporated–Expand-

able ion Analyzer EA 920) with a combined glass

electrode was used for pH measurements.

3. Results and discussion

The water-soluble polymer PEI was considered in this

preliminary phase of our work. It shows a good affinity

for the model ion Cu2+ and has the advantage of no

release of counter ions in the treated water with respect

to polymers that work with an ion-exchange mechanism.

In Fig. 2, the mechanism of PEI–copper interaction is

reported [16], where the lone-pair of nitrogen binds the

copper according to the acid and base Lewis theory.

The mechanism of PEI–copper interaction can be

described by the following equilibrium reactions:

PEIþ nH2O"PEIHnþn þ nOH�; ð1Þ

PEIþ aCu2þ"PEICu2aþa ; ð2Þ

where 0pnp %n and 0pap %a with %n equal to the number

of monomers contained in a single polymeric chain and

%a representing the maximum complexation ratio of the

polymers with copper ions ( %a ¼ %n=4 as showed in the

idealised structure previously reported). In particular,

considering the longer polymeric chain (MW 60kDa)

and considering the monomeric unit –CH2–CH2–NH–

(MW 43.062Da) we obtain that %n ¼ 1393:Reactions (1) and (2) are competitive for the polymer

because, depending on pH conditions, it is able to

complex copper ions by means of Eq. (2) or stays

in aqueous solution like PEI Hnþn at low pH incapable to

interact with copper. Measuring the pH of PEI in

aqueous solutions, the Keq of Eq. (1) was practically

equal to zero, meaning that this equilibrium reaction is

hardly shifted at left. So, the polymer at its natural pH in

water stays prevalently as PEI, and not in the form

PEI Hnþn :

First step of this research consisted in the determina-

tion of optimal chemical conditions (pH) for copper

complexation (bound) and de-complexation (release).

The determination of release condition is fundamental

for recovering and recycling the binding polymeric

agent. Indeed, it should be taken into account that the

PAUF process appears to be economically more feasible

if the polymer could be regenerated and reused, so that

the process should be represented as reported in Fig. 3.

Complexation and de-complexation conditions were

determined by means of some tests conceptually very

similar to L–L extraction. They were carried out in

isothermal conditions at a temperature of 2571�C by

preparing 20ml of aqueous solutions containing poly-

mer and copper at concentrations respectively of 150

and 50 ppm, and changing the pH. In order to evaluate

the influence of polymer molecular weight on copper

complexation, these experiments were realised both with

PEI 10,000 and PEI 60,000. To quantify the copper–

polyethylenimine (Cu–PEI) complex formation, the

spectrophotometric technique was used. By previous

scanning of various samples, the peaks of absorbance vs.

wavelength showed a maximum absorbance for Cu–PEI

complex in aqueous media at a wavelength of 620 nm.

By taking advantage of complex reading at this

wavelength whilst no reading was observed for Cu2+

alone, it was possible to establish if the complex was or

not formed by simple experiments in test tubes without

using the membrane separation process. The complexa-

tion–decomplexation process was quantified by plotting

ARTICLE IN PRESS

Recovered

Metal solution

Polymer Recycle

Metal containing

Feed

Permeate (water to reuse or discharge)

Retentate

Complexation

Polymer make-up

MEMBRANE

STEP Polymer

Regeneration

Fig. 3. Schematic principle of the PAUF separation process.

0

20

40

60

80

100

2 4 6 8 10pH

C % 300/50

150/5050/50

Fig. 4. Cu–PEI complex formation C%ð¼ ðABS=ABSmaxÞ100Þ vs. pH in complexation tests of PEI 10,000 (300, 150 and

50mg/l) with copper (50mg/l).

0

20

40

60

80

100

0 30 60 90 120 150

Copper concentration [mg/l]

C % PEI 60000

PEI 10000

R2 = 0.9857

0

40

80

120

0 100 200 300 400

Polymer concentration [mg/l]

[Cu

2+] m

ax

(a)

(b)

Fig. 5. (a) Cu–PEI complex formation C%ð¼ ðABS=ABSmaxÞ100Þ vs. copper concentration (initial PEI concentration=

150mg/l, pH=6) and (b) determination of the binding capacity

of PEI 60,000 (pH=6).

R. Molinari et al. / Water Research 38 (2004) 593–600 597

the complexation percentage C%¼ ðABS=ABSmaxÞ100; where ABSmax is the maximum value of the

absorbance obtained from the experiments which

corresponds to the maximum amount of complex

(100%). Obtained results for PEI 10,000, reported in

Fig. 4, show that this polymer is able to complex copper

ion at pH 6 or higher, while the decomplexation happens

at pHo3 ðC%o10%Þ: The results of complexation tests

with PEI 60,000 are not reported because the obtained

data were practically equal to that ones obtained with

the smaller chain-polymer. Indeed, the number of single

complexes in Fig. 2, [Cu2+–(NH)4], depends only on

total monomeric units present in the overall polymer

chains and not on polymer molecular weight. Similar

results were obtained by working at different polymer

concentrations (300 and 50 ppm), showing that pH of

maximum bonding does not depend also on polymer

concentration.

These results agree with the chemical mechanism of

polymer–copper interactions. Indeed, at high pH the

complexation reaction (2) takes place.

In order to determine the bonding capacity (satura-

tion condition) of PEI (maximum copper amount, e.g.

grams, that can be complexed by a fixed amount, e.g.

1 g, of polymer), some complexation tests were carried

out with a polymer concentration of 150mg/l (volu-

me=20ml) and changing copper concentration at a

fixed pH value (equal to 6). It should be taken into

account that one important cost of PAUF process is

represented by polymer consumption and its bonding

efficiency: this justify the convenience to use the polymer

at its maximum complexation capacity. Obtained

results, reported in Fig. 5a for PEI 10,000 and 60,000,

show that maximum copper that can be complexed by

150mg/l PEI is equal to 50mg/l, that is 0.333mg Cu2+/

mg PEI. This value is also confirmed in Fig. 5b for

various concentration values of Cu2+ and polymer. The

excess of copper remains in solution like hydroxide. In

fact, taking into account that the solubility product

constant Ksp CuðOHÞ2 ¼ ½Cu2þ�½OH��2 ¼ 10�19:9; at 25�C,maximum feed pH to avoid copper hydroxide formation

ARTICLE IN PRESS

0

100

200

300

150 300 450 600Polymer concentration in the retentate [mg/l]

Flu

x [l

/h*m

2 ]

Iris 10 kDaPAN 40 kDaDOW GR 40DOW FS 40 PPIris 30 kDa

Fig. 6. Comparison of flux through the five membranes by

increasing polymer concentration (values at steady state,

P ¼ 2 bar, PEI=Cu2þ ¼ 3).

0

2

4

6

8

10

150 300 450 600Polymer concentration in the retentate [mg/l]

Co

pp

er C

p [

mg

/l]

Iris 10 kDaPAN 40 kDaDOW GR 40DOW FS 40 PPIris 30 kDa

Fig. 7. Comparison of copper concentration in the permeate

(Cp) for the five membranes by increasing polymer concentra-

tion (values at steady state, P ¼ 2 bar, PEI=Cu2þ ¼ 3).

96.0

98.0

100.0

150 300 450 600

Polymer concentration in the retentate [mg/l]

R%

Iris 10 kDa

Iris 30 kDa

PAN 40 kDa

DOW GR 40

DOW FS 40PP

Fig. 8. Comparison of copper rejections (R%) for the five

membranes by increasing polymer concentration (values at

steady state, P ¼ 2 bar, PEI=Cu2þ ¼ 3).

R. Molinari et al. / Water Research 38 (2004) 593–600598

and precipitation is approximately 5.6 for an aqueous

concentration of copper equal to 50mg/l, while in these

complexation tests operative pH was 6.

Important result of the complexation tests is the

identical binding capacity obtained operating with PEI

10,000 and 60,000. This is a consequence of the

concentration unit used: in fact, PEI binding capacity

depends only on the number of complexation sites that

are the same for a same weight amount of polymer.

Obviously, this is not applicable when referring to molar

concentration (polymer moles/litres of solution).

Adding the previous consideration on identical

operative pHs and binding capacity for the two size of

PEI used and taking into account that in PAUF the

complexation step is followed by a membrane filtration,

the PEI 60,000 is more interesting than the smaller one,

permitting the use of membranes with bigger pores for

obtaining low operating costs.

From the above results the operative conditions for

ultrafiltration tests were ratio PEI/Cu2+=3(w/w) and

pH=6.

Ultrafiltration tests were carried out using five

different membranes (see Table 1), two operative

trans-membrane pressures (2 and 4 bar), pH approxi-

mately equal to 6 and three different weight concentra-

tions of PEI and Cu2+ (150/50, 375/125, 600/200).

Working at increasing PEI/Cu2+ concentrations per-

mitted to simulate the increase of retentate concentra-

tion in a hypothetical industrial plant where the

permeate free of metals is withdrawn using the PAUF

technique. We used this approach because of the small

volume of permeate collected during an ultrafiltration

run (as a consequence of the small useful membrane

surface area); indeed, the increase of concentration in

the retentate by a direct withdrawn of permeate would

require a lot of working hours of the laboratory plant.

Each test, at different copper and polymer concentra-

tions, was carried out by starting with a new set of the

five membranes: in fact, to realise a process with an

industrial applicability it is certainly important to

evaluate membrane fouling, regeneration and reuse,

but goal of our preliminary tests was to evaluate and

compare membrane performances at increasing reten-

tate concentrations, which practically results in an

increase of membrane fouling and/or concentration

polarisation.

Obtained results, summarised in Figs. 6–8, show that

increasing copper and then polymer concentration (ratio

PEI/Cu2+=3 fixed) in the retentate, the separation

efficiency (R%) decreases, that will results in a copper

and polymer concentrations increase in the permeate

and a little decrease of permeate flux. By increasing

polymer concentration in the retentate (Fig. 8), rejection

first decreases, because of fouling, but increasing

retentate concentration this tendency changes, because

of the formation of a selective dynamic layer (by

concentration polarisation) that improves the separa-

tion. This causes a little permeate flux decrease too,

because of mass transfer resistance increase. The

inspection of the membranes at the end of each run

permitted to confirm cake formation: in fact, each used

membrane presented a thin layer on its filtering surface.

This cake was cerulean, practically the colour of the

polymer–copper complex, but it not gave too much

intensity of the fouling after simple washings with tap

ARTICLE IN PRESSR. Molinari et al. / Water Research 38 (2004) 593–600 599

water. Indeed, the initial water permeate flux obtained

with demineralised water (see Table 1, column at 2 bar)

was about the same of that one obtained in operating

conditions (see Fig. 6).

It should be taken into account that an optimal

PAUF processes should generate high permeate flux (JP)

with low copper concentration (Cp). So, in order to

compare membrane performances, an appropriate para-

meter Jp=Cp was introduced. This parameter has no

dimensional significance, but it answers to the previous

requirements to optimise PAUF processes.

Data of our optimisation parameter Jp=Cp; reportedin Figs. 9 and 10 at 2 and 4 bar, respectively, show that

the PAN 40 kDa membrane gives the best combination

of the two parameters. Furthermore, it is better

operating at P ¼ 2 bar rather than at 4 bar as the higher

Jp=Cp value shows.

The economical feasibility of PAUF process depends

also on polymer regeneration, so some UF tests were

carried out in the laboratory plant, with a set of five

membrane previously used and with the following

operative conditions: PEI=150 ppm; Cu=50 ppm;

pH=3 (de-complexation conditions). The permeates

withdrawn at established time were analysed to deter-

mine copper and TOC concentrations: obtained data

0

200

400

600

800

150 300 450 600

Polymer concentration in the retentate [mg/l]

(Jp

/Cp

)

Iris 10 kDa

PAN 40 kDa

DOW GR 40

Iris 30 kDa

DOW FS 40 PP

Fig. 9. Comparison of Jp=Cp for the five membranes by

increasing polymer concentration (values at steady state,

P ¼ 2 bar, PEI=Cu2þ ¼ 3).

0

200

400

600

150 300 450 600Polymer concentration in the retentate [mg/l]

(Jp

/Cp

)

Iris 10 kDa

PAN 40 kDa

DOW GR 40

Iris 30 kDa

DOW FS 40 PP

Fig. 10. Comparison of Jp=Cp for the five membranes by

increasing polymer concentration (values at steady state, P ¼ 4

bar, PEI=Cu2þ ¼ 3).

showed that all the copper passed through the mem-

brane, while the polymer remained in the retentate

(rejection of 95% with PAN 40kDa membrane), that

means a good possibility of polymer regeneration,

recovery and reuse.

4. Conclusions

The described study on polymer assisted ultrafiltra-

tion shows: (i) the importance to use optimal chemical

conditions to obtain a maximum binding capacity of the

polymer; (ii) the role of different types of UF

membranes in order to employ this process in metal

ions removal from various types of wastewaters. In the

case of Cu2+ removal by its complexation with PEI best

results were obtained for the membrane PAN 40 kDa,

reaching an average copper concentration in the

permeate of 2mg/l and a flux of 135.4 and 156.5 l/h.m2

at 2 and 4 bar, respectively. The obtained results show

that use of PAUF process with PEI does not reach a

complete removal of the metal, but can reach the

objective of the purification process that is to decrease

metal concentration down a certain value required by

reuse or fixed by water laws for discharge.

Acknowledgements

The authors wish to thank the National Interuniver-

sity Consortium ‘‘Chemistry for the Environment’’

(INCA) which partially supported this work within the

Sisifo Project and the National INCA Plane ‘‘Remedia-

tion of contaminated soil’’.

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