Method for removal of monovalent ions from ZnSO.sub.4 electrolyte by electrodialysis
US4715939A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 21, 1987 |
| Grant date | Dec 29, 1987 |
| Priority date | — |
| Expiry date | Apr 21, 2007 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB01D2321/162
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
Monovalent ions, especially chloride and fluoride, but also thallium, sodium and potassium are efficiently removed from ZnSO.sub.4 electrolyte by electrodialysis. Monovalent anions are removed using alternating monovalent anion permselective membranes and cation exchange membranes. Monovalent anions and cations are removed using alternating monovalent anion and monovalent cation permselective membranes. Electrodialysis is carried out under turbulent conditions, at up to 60.degree. C., a differential membrane pressure of less than 150 kPa, a current density of 10 to 500 A/m.sup.2, and a pH of less than 5.5. Where both chloride and fluoride are removed a pH of 3.5 to 5.5 is maintained. Deposition of manganese and zinc on the electrodes is minimized by at least one of a number of means including arranging the membranes such that the end membranes are monovalent anion permselective; selecting a large electrode rinse flow; adding a small amount of soluble antimony and/or cobalt; and using a cathode made of a material that promotes hydrogen evolution over zinc deposition. The electrode compartments are preferably rinsed with a 0.1 to 1.0 M Na.sub.2 SO.sub.4 solution at pH 0 to 4.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.