SESSION 7

TWO-FLUID SYSTEMS AND APPLICATIONS

Chairmen: J.C. Merchuk, J.I. Ramos

THE APPLICATION OF LIQUID MEMBRANE PROCESSES IN WASTEWATER TECHNOLOGY. PART.1 SEPARATION, CONCENTRATION AND THE SELECTIVE RECOVERY OF COPPER IONS FROM DILUTE AQUEOUS SOLUTIONS AND WASTEWATERS

Viorica Dalea*,**, Smaranda Mâsu**, V.Cocheci+*,**
*"Politehnica" University of Timisoara
**Research Institute for Wastewater Treatment - Branch of Timisoara

1. INTRODUCTION

The treatment of some wastewaters by using ELM (emulsion liquid membrane) has been defined as a main process by N.N.Li1 (on the middle of XX century).

This process consists in a mass transfer of pollutants due to some physical and chemical gradients. The working system has been represented by AIII/UII/AI, (wastewater/organic phase/internal water phase for capture and concentration of pollutants),a double emulsion obtained by primary emulsion A I/UII stabilised with surfactant distribution in the continuous phase AIII (waste water)2-3.

2. EXPERIMENTAL

Emulsion of type A I/UII has been obtained by using of a hydrodynamic regime consisting in a very rapid stirring (1200 rpm) for 15 minutes, applied to a mixture of one part water phase containing NaOH 0.25 M and one part of organic phase containing carrier and surfactant. The used compounds are presented in table 1.

Table l.
AI/UII emulsions used for copper extraction from wastewater (AIII)
(working ratio AIII : AI/UII = 3:1 in volumes)
organic phase: Romanian kerosene

ELM type Tensioactive agent Carrier Internal phase
ELM 1 Alkyl dymethyl benzyl ammonium chloride p.a. 0.15 %Fatty acids Acetic acid solution p.a. 2 %
ELM 2 Span 80 Fluka p.a. 2 % PEG p.a. 2000, 3-5 % NaOH sol. p.a. pH = 9
ELM 3 Span 80 Atlas p.a. 2 % Naphtenic acids, 5-10 % H2SO4 sol. p.a. pH = 2
ELM 4 Span 80 Atlas p.a. 1.75 % PEG p.a. 6000 NaOH sol. p.a. pH = 9
ELM 5 Span 80 indigen p.a. 3.5 % Rubeanic acid H2SO4 sol. p.a. pH = 2
ELM 6 Span 80 indigen p.a. 1.2 % NH4Cl/NH4OH Ammoniacal buffer, pH = 10
ELM 7 Span 80 indigen p.a. 1.2 % TOA p.a. KJ sol. p.a. 2 %, pH = 2

3. RESULTS AND DISCUSSIONS

The distribution of simple emulsion AI/UII in AIII was made by a hydrodynamic regime presented in Table 2.

Table 2.
Efficiencies of ELM in the treatment of wastewaters containing Cu2+ ions.

ELM type Hydrodynamic conditions Wastewater Ci
[ppm] 		Process efficiency
[%]
Stirring speed
[rot/min.] 		Stirring time
[s]
ELM 1 500 300 l000 70
ELM 2 200 300 1000 50
ELM 3 150 - 200 300 1000 87
ELM 4 200 300 1000 75
ELM 5 200 300 1000 62
ELM 6 250 90 190 80
ELM 7 250 240 240 68.8
The swelling phenomena of AI/Uß emulsion during the distribution in the AIIIlLlII/AI system (due to wastewater osmosis) were limited by an adequate quantity of tenside and hydrodynamic regime (slow stirring)

The treatment efficiencies of wastewater (AIII) with primary emulsion AI/UII ranged between 68.8 - 80 %, under optimum hydrodynamic conditions: stirring speed = 250 rpm and stirring time : 90 - 240 s. (carner was trioctylamine, TOA)

4. CONCLUSION

  1. Different types of ELM can be prepared to provide treatment efficiencies for wastewater with Cu2+ ions in the range of 50-87 % and a satisfactory final concentration for a single step of treatment by the establishing optimal conditions concerning tensioactive agent, internal phase, carrier.
  2. Primary emulsion application should follow a particular hydrodynamic regime regarding the speed and the duration of the slow stirring to provide high efficiencies.
  3. In this work, we have been emphasised on swelling phenomena of emulsion AI/UII occurred during the treatment of some wastewaters. These phenomena have a negative influence on the treatment eff ciency. Swelling phenomena could be diminished both by ELM formulation and by adequate hydrodynamic conditions of slow stirring.

5. SELECTIVE REFERENCES

  1. Li, N.N., US Patent 3.410,794, November, I ,1968.
  2. Franckenfeld, J.W., Cahu, R.P. and Li, N.N., Sep. Sci. Tech.,16 (4),1981, p.385.
  3. Ho, W. S. and Li, N.N., "Modelling of Liquid Membrane Extraction Process", Hydrometallurgical Process Fundamentals, Ed. R.G. Bautista NY, Plenum Press,1984.

THE APPLICATION OF LIQUID MEMBRANE PROCESSES IN WASTEWATER TECHNOLOGY. PART 2. SEPARATION, CONCENTRATION AND THE SELECTIVE RECOVERY OF PHENOL FROM DILUTED AQUEOUS SOLUTIONS AND WASTEWATERS.

Smaranda Mâsu**, Viorica Dalea*,**, V.Cocheci*,**
* "Politehnica" University of Timisoara
** Research Institute for Wastewater Treatment - Branch of Timisoara

1. INTRODUCTION

The use of ELM (emulsion liquid membrane) for the treatment of some waters containing organic pollutants is based on the organic species (A) permeation principle through organic barrier, corresponding to permeation laws1, 2.

Permeation process is coupled in internal phase with a reaction by wich reaction agent B consumes permeated species and, thus, the resulted compound C can not cross the organic film in the opposite sense:

C6H5OH + NaOH --> [C6H5O][Na] + H2O (1)
CH3COOH + NaOH --> [CH3COO][Na] + H2O (2)
A = C6H5OH, CH3COOH; B = NaOH, C =[C6H5O][Na], [CH3COO][Na]

Equation of permeation is:

dn/dt = - DS dc/dx (3)

where:
dn/dt = quantity of material permeating across a given area of membrane/time;
D = diffusion coefficient, constant;
S = transfer area;
dc/dx = the concentration difference of the permeation species on the membrane thickness;
x = membrane thikness.

Because the permeation rate is directly proportional with pollutant concentration in external phase (and when pollutant A permeation is coupled with its irreversible blocking reaction in the internal phase) the following equation is valid :

ln(Cf/Ci)=-D' R t (4)

where:
D/x2 = D'= permeation constant
VELM/VWW = R, working ratio;
VELM = AI/UII emulsion volume;
VWW = feed phase volume

2. EXPERIMENTAL

The generation of primary emulsion AI/UII and of the double one has been carried out according to the description in Part l.

Analyses of pollutant species in initial and treated water are as follows: phenol by HLPC, acetic acid by potentiometric titration, organic load as COD (Chemical Oxygen Demand).

The experimental study has set up conditions to provide that reactions (1) and (2) proceed in function of the capture agent amount, NaOH, introduced in the internal phase; 0,5M NaOH for ELM I; 0,25M NaOH for ELM II.The two types of ELM (I-II) would be used in two slow stirring hydrodynamic regimes: 25 rpm (ELM I - l, ELM II -1 ) and 250 rpm (ELM I - 2, ELM II - 2). The variants for the treatment of water containing a mixture a phenol and acetic acid by ELM I - l, ELM I - 2, ELM II - l, and ELM II - 2 carry out a disproportion of the pollutant mixture.

3. RESULTS AND DISCUSSIONS

Domains of permeation for phenol in phenol/acetic acid mixture characterized by D' (permeation constant) are given in Tab. l.

Table 1
Permeation rate constants for different t

ELM

I - 1

I - 2

II -1

II - 2

1. Permeation Rate Constant (for t=2 s), D' phenol sec-1

1.77

2.0

1.63

1.71

2. Permeation Rate Constant (for t=30 s), D' phenol sec-1

0.15

0.20

0.21

0.22

The permeation rate constants were determined using experimental data obtained in laboratory using equation 4.

In Fig. l . organic load (COD) of the water treated by ELM variants are represented as function of contact time.


Figure 1. Variation of COD in wastewater when ELM 1- 4 are applied

4. CONCLUSION

As a function of the required wastewater treatment degree, the separation efficiencies for phenol and acetic acid are in correlation both with the COD values in treated water and with the secondary phenomena of emulsion swelling, occurring during the treatment.

5. SELECTIVE REFERENCES

  1. Cahn, R.P. and Li, N.N., Sep. Sci. 9(6),1974, p.505.
  2. Nian-Xi Yan, Song - An Huang and Ya - Jun Shi, Sep. Sci. Techn. 22 (283),1987, p.801.

VIABILITY OF THE LIQUID-LIQUID SEPARATION OF CADMIUM FROM PHOSPHORIC ACID USING ALIQUAT 336 AS EXTRACTANT

A.M. Urtiaga, S. Zamacona, A. Irabien, I. Ortiz
Dpto. de Quìmica. E. T. S.I.I. y T. Universidad de Cantabria. Avda. de los Castros S/N.
39005 Santander. ESPAÑA

In the wet phosphoric acid process, the heavy metals contained in the phosphate rock get redistributed between the phosphoric acid and waste phosphogypsum. The most frequent metals are Cd, Ni, Pb, Zn, Cu, Mn, Mo, Hg as well as some radionucleides, that in the manufacture of phosphate fertilizers finish in the solid product. Cadmium is one of the most toxic elements to the living body as builds up. Therefore due to the gradually stricter standards for cadmium content of fertilizers, the fertilizer industry is required to introduce effective technologies for the removal of cadmium from phosphoric acid.

In this work, and as a part of a general project under the frame of the european Avicenne program, the viability and analysis of the selective removal of cadmium from phosphoric acid by means of the non-dispersive liquid-liquid extraction technology, NDSX. using Aliquat 336 as selective organic extractant, has been studied.

The industrial phosphoric acid used in this study, has been kindly supplied by FERTIBERIA. The metallic content was characterized by means of an ICP spectrophotometer. The initial acid metallic content was Cd,16 mg/l; Cr, 292 mg/l; Cu, 34 mg/l; Fe, 2013 mg/l; Ni, 48 mg/l; Pb, 8 mg/l and Zn, 335 mg/l. The cadmium concentration was raised up to 50 mg/l previous to extraction runs.

Following a literature survey the group of thiophosphinic acids (commercialized as CYANEX 301 and CYANEX 302) seemed to be adequate compounds for the selective extraction of cadmium from highly acidic media.

Encouraging results were obtained when testing a synthetic phosphoric acid ( 30% P2O5) containing 50 mg/1 of Cd as unique heavy metal, employing CYANEX 302 as extractant and leading to Cd extraction efficiencies around 99% (1,2). However, the behaviour of CYANEX 302 in the cadmium extraction from industrial phosphoric acid is completely disturbed by the presence of copper. It has been experimentally proved that the simultaneous extraction of Cd(II) and Cu(II) from phosphoric acid by CYANEX 302 involves the reduction of Cu(II) to Cu(I) and the accompanying oxidation of CYANEX 302, yielding a no longer active extractant. Recent studies published in the literature support this mechanism of deactivation. Under these circumstances, the search of an adequate extractant for the cadmium removal from industrial phosphoric acid is required.

In this work, the viability study of the removal of Cd using of ALIQUAT 336 as organic extractant is presented.

Under the experimental conditions of this study, a cadmium removal efficiency using ALIQUAT 336 of 95% has been obtained using an organic extractant phase with ALIQUAT 336 (30%), isodecanol (30%) and commercial kerosene (40%).

ALIQUAT 336 extracts the Cd(II) from the industrial phosphoric acid in the form of cadmium phosphates, accompanied by Ni, Fe and a little amount of phosphoric acid. No extraction of Cu is observed, since the concentration of the metal in the phosphoric acid remains unchanged.

The regeneration of the loaded ALIQUAT 336 is performed using water, observing the reextraction of Cd, Zn, Fe and phosphoric acid.

REFERENCES

  1. I. Ortiz, S. Zamacona, B. Galán, A.I. Alonso, A.M. Urtiaga, A. Irabien.(1995)."Selective extraction of cadmium from phosphoric acid in hollow tiber modules". 7th Mediterranean Congress of Chemical Engineering.
  2. A.I. Alonso, A.M. Urtiaga, S. Zamacona, A. Irabien, I. Ortiz. (1996). "Kinetic modelling of Cd removal from phosphoric acid by non-dispersive solvent extraction". Journal of Membrane Science (submitted).

SEPARATION OF CADMIUM FROM PHOSPHORIC ACID CONTAINING Cu2+ AND Cd2+ USING SURFACTANT LIQUID MEMBRANES

T. Gallego Lizon, E.S. Pérez de Ortiz
Department of Chemical Engineering and Chemical Technology
Imperial College
London SW7 1NA
United Kingdom

ABSTRACT

A two stage process for the separation of Cd and Cu from raw phosphoric acid is proposed in which copper(II) is extracted first by conventional solvent extraction using Acorga P50 as the extractant. Cyanex 302 is then used as the reagent for the recovery of Cd(II) with an emulsion liquid membrane. The performance of the emulsion liquid membrane (ELM) in the extraction of Cd was investigated covering wide ranges of extractant and surfactant concentrations, internal phase to organic ratios, homogenizer speed and stirring speed in the stirred tank. The recovery of Cu using the ELM was also investigated but no surfactant was found that produced a sufficiently stable emulsion at the conditions of the process.

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