Abstract
A flow-through yttria-stabilized zirconia (FTYSZ) electrode has been employed for pH measurements at 250 °C in concentrated electrolyte systems relevant to hydrometallurgical processing of nickeliferous laterites. Experiments were conducted using a custom-made flow-through titanium electrochemical cell specially designed for high-temperature potentiometric pH measurements. In the present work, we assess the accuracy and validity of pH measurements with theory at 250 °C on concentrated sulfate process solutions. First, binary sulfuric acid-water solutions were measured at concentrations ranging from 0.05 to 0.5 mol kg-1 and showed 0.3 pH unit increase on the average between 25 and 250 °C. The measurements were then extended to ternary and quaternary systems containing 0.0076-0.038m Al2(SO4)3 and 0.0276-0.276m MgSO4, respectively. Autoclave passivation against corrosion was successfully achieved using sodium chromate or hydrogen peroxide. In this technique, the potentials are measured against a Ag/AgCl flow-through external reference electrode (FTEFE). A reference solution of 0.1 mol kg-1 NaCl(aq) flows permanently through the electrode at a constant flow rate, so that the thermal liquid junction and streaming potentials are kept constant. The experimental results were compared with theory using available thermodynamic data for estimating the quality of pH measurements. An average difference of 0.15 pH unit was observed between measured and theoretical values at temperature.
| Original language | English |
|---|---|
| Pages (from-to) | 131-139 |
| Number of pages | 9 |
| Journal | Hydrometallurgy |
| Volume | 68 |
| Issue number | 1-3 |
| DOIs | |
| State | Published - Feb 1 2003 |
| Externally published | Yes |
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Keywords
- pH measurement
- Sulfuric acid-water solution
- Yttria-stabilized zirconia sensor
ASJC Scopus subject areas
- Geochemistry and Petrology
- Geotechnical Engineering and Engineering Geology
Cite this
Potentiometric pH measurements in acidic sulfate solutions at 250 °C relevant to pressure leaching. / Seneviratne, D. S.; Papangelakis, V. G.; Zhou, Xiangyang; Lvov, S. N.
In: Hydrometallurgy, Vol. 68, No. 1-3, 01.02.2003, p. 131-139.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Potentiometric pH measurements in acidic sulfate solutions at 250 °C relevant to pressure leaching
AU - Seneviratne, D. S.
AU - Papangelakis, V. G.
AU - Zhou, Xiangyang
AU - Lvov, S. N.
PY - 2003/2/1
Y1 - 2003/2/1
N2 - A flow-through yttria-stabilized zirconia (FTYSZ) electrode has been employed for pH measurements at 250 °C in concentrated electrolyte systems relevant to hydrometallurgical processing of nickeliferous laterites. Experiments were conducted using a custom-made flow-through titanium electrochemical cell specially designed for high-temperature potentiometric pH measurements. In the present work, we assess the accuracy and validity of pH measurements with theory at 250 °C on concentrated sulfate process solutions. First, binary sulfuric acid-water solutions were measured at concentrations ranging from 0.05 to 0.5 mol kg-1 and showed 0.3 pH unit increase on the average between 25 and 250 °C. The measurements were then extended to ternary and quaternary systems containing 0.0076-0.038m Al2(SO4)3 and 0.0276-0.276m MgSO4, respectively. Autoclave passivation against corrosion was successfully achieved using sodium chromate or hydrogen peroxide. In this technique, the potentials are measured against a Ag/AgCl flow-through external reference electrode (FTEFE). A reference solution of 0.1 mol kg-1 NaCl(aq) flows permanently through the electrode at a constant flow rate, so that the thermal liquid junction and streaming potentials are kept constant. The experimental results were compared with theory using available thermodynamic data for estimating the quality of pH measurements. An average difference of 0.15 pH unit was observed between measured and theoretical values at temperature.
AB - A flow-through yttria-stabilized zirconia (FTYSZ) electrode has been employed for pH measurements at 250 °C in concentrated electrolyte systems relevant to hydrometallurgical processing of nickeliferous laterites. Experiments were conducted using a custom-made flow-through titanium electrochemical cell specially designed for high-temperature potentiometric pH measurements. In the present work, we assess the accuracy and validity of pH measurements with theory at 250 °C on concentrated sulfate process solutions. First, binary sulfuric acid-water solutions were measured at concentrations ranging from 0.05 to 0.5 mol kg-1 and showed 0.3 pH unit increase on the average between 25 and 250 °C. The measurements were then extended to ternary and quaternary systems containing 0.0076-0.038m Al2(SO4)3 and 0.0276-0.276m MgSO4, respectively. Autoclave passivation against corrosion was successfully achieved using sodium chromate or hydrogen peroxide. In this technique, the potentials are measured against a Ag/AgCl flow-through external reference electrode (FTEFE). A reference solution of 0.1 mol kg-1 NaCl(aq) flows permanently through the electrode at a constant flow rate, so that the thermal liquid junction and streaming potentials are kept constant. The experimental results were compared with theory using available thermodynamic data for estimating the quality of pH measurements. An average difference of 0.15 pH unit was observed between measured and theoretical values at temperature.
KW - pH measurement
KW - Sulfuric acid-water solution
KW - Yttria-stabilized zirconia sensor
UR - http://www.scopus.com/inward/record.url?scp=0037322069&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037322069&partnerID=8YFLogxK
U2 - 10.1016/S0304-386X(02)00198-6
DO - 10.1016/S0304-386X(02)00198-6
M3 - Article
AN - SCOPUS:0037322069
VL - 68
SP - 131
EP - 139
JO - Hydrometallurgy
JF - Hydrometallurgy
SN - 0304-386X
IS - 1-3
ER -