Potentiometric pH measurements in acidic sulfate solutions at 250 °C relevant to pressure leaching

D. S. Seneviratne, V. G. Papangelakis, Xiangyang Zhou, S. N. Lvov

Research output: Contribution to journalArticle

14 Citations (Scopus)

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 languageEnglish
Pages (from-to)131-139
Number of pages9
JournalHydrometallurgy
Volume68
Issue number1-3
DOIs
StatePublished - Feb 1 2003
Externally publishedYes

Fingerprint

Leaching
Sulfates
leaching
sulfate
electrode
Electrodes
streaming potential
Chromates
chromate
acid water
Electrochemical cells
laterite
Yttria stabilized zirconia
Autoclaves
Titanium
Sulfuric acid
Passivation
Hydrogen peroxide
sulfuric acid
electrolyte

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 journalArticle

Seneviratne, D. S. ; Papangelakis, V. G. ; Zhou, Xiangyang ; Lvov, S. N. / Potentiometric pH measurements in acidic sulfate solutions at 250 °C relevant to pressure leaching. In: Hydrometallurgy. 2003 ; Vol. 68, No. 1-3. pp. 131-139.
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