Recovery of Sulfuric Acid from Liquid

Effluents by Electrodialysis

Juan Patricio Ibáñez & Ana Karina VásquezDepartamento de Ingeniería Metalúrgica y de Materiales

Universidad Técnica Federico Santa María

Introduction (i)

H2SO4 important and costly reagent used during copper production, it

is present in almost all the liquid effluents of the extractive processes.

Effluents high acidity, high level of sulphate/bisulphate. Treatment of

these effluents solid wastes, which needs to be manage according to

the DS 148.

Bleeds for controlling impurities in EW and/or ER H2SO4 liqueurs,

which are not always treated but are diluted and returned to previous

processes or transformed in “disposable” effluents.

Lix-SX-EW requirement of H2SO4 ≈3.2 ton/ton of Cu

Cost of H2SO4 ≈120 US$/ton

Introduction (ii)

Deficit of ≈2 Mton of acid per year is projected until 2013 in Chile

Recocery of acid

Solvent Extraction (Cyanex 923, TEHA, etc.)

Ion Exchange (Anion resine, etc.)

Dialysis (anion membrane)

Alternative electro dialysis

Introduction (iii)

ED membrane separation technology in which ionized species are

transported through ion-exchange membranes by an external electric field.

Cation

Memb.

Anion

Memb.

M+

M+

MXM+MX

X-

X-

X-

X-X

-

M+

M+

Electrical Field

Working

Solution(X-, M+, MX)

Anion rich

SolutionCation rich

Solution

Cathode(SS 316-L)

Anode(Pb)

CM(Neosepta)

AM(Neosepta)

Chambers(Acrylic)

Cation Flux

Anion Flux

C

C

A

CA C

Experimental (i)

W

S

Experimental (ii)

WS1. H2SO4 180 g/L + Cu 40 g/L

2. H2SO4 90 g/L + Cu 20 g/L

3. H2SO4 50 g/L + Cu 10 g/L

4. H2SO4 180 g/L + Co 0.2 g/LAnalysismetals by AAS

acid by titration

A , AC, CC & C H2SO4 20 g/L < WS

Experimental conditions Time = 180 mim

i = 100, 300 & 700 A/m2

Results & Discussion (i)

CM CMAM AM

(A) (AC) (WS) (CC) (C)

+ -SO42-

HSO4-

H+

HSO4-

SO42-H+

H+ + HSO4- H2SO4 H+ + HSO4

- H2SO4

2H+ + SO42- H2SO4 2H+ + SO4

2- H2SO4

T ime, m in

0 50 100 150 200

H2S

O4,

mm

ol

0

10

20

30

40

50

60

70

80

100 A/m2

300 A/m2

700 A/m2

Results & Discussion (ii)

Effect of current density

Lineal behaviour…

↑i ↑H2SO4

i, A /m2

0 200 400 600 800

Re

co

ve

ry

H2S

O4,

mo

l/h

/m2

0

2

4

6

8

10

12

14

16

18

20

W S-3

W S-2

W S-1

Results & Discussion (iii)

Effect of electrolyte´s concentration

Lineal behaviour…

↑[H2SO4]

↓Recovery

?

V iscosity, cP

1.0 1.2 1.4 1.6 1.8

Re

co

ve

ry

H2S

O4,

mo

l/h

/m2

0

4

8

12

16

20

100 A/m2

300 A/m2

700 A/m2

Results & Discussion (iv)

Electrolyte´s viscosity

Results & Discussion (v)

Purity of H2SO4 recovered

i, A/m2

RecoveryWS-1Purity TCu Recovery

WS-4Purity TCox102

100 1.66 99.1 0.30 0.95 99.9 0.09

300 2.92 97.6 0.65 2.15 99.9 0.15

700 7.82 94.9 1.34 5.97 99.9 0.24

Recovery rate (mol/h/m2), putity (%) & Cu-Co Transport (mol/h/m2)

i, A /m2

0 200 400 600 800

SE

C,

kW

h/k

g

0

1

2

3

4

5

Results & Discussion (v)

SEC for H2SO4 recovery

Conclusions

Recovery of H2SO4 by ED shows promising results

and projections.

700 A/m2 recovery of 7.82 mol/h/m2, with ≈95%

purity and a SEC 4.1 kWh/kg, from a solution having

180 g/L H2SO4 + 40 g/L of Cu

THANKS