Method for recovery of aqueous wash in phosphate chemical conversion and apparatus for metal surface treatment
US6391206B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 11, 2000 |
| Grant date | May 21, 2002 |
| Priority date | — |
| Expiry date | Dec 11, 2020 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23C22/00
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
This invention is related to a method for recovery of aqueous wash in a phosphate chemical conversion of a shaped metal product involving carrying out chemical conversion and subsequent cleaning with water,wherein said cleaning with water is performed in one or more stages and comprisesa step of withdrawing aqueous wash from a first cleaning stage and adjusting the pH of the wash with at least one acid selected from the group consisting of phosphoric acid, nitric acid, hydrofluoric acid, hydrosilicofluoric acid and fluoroboric acid,a step of treating said pH-adjusted aqueous wash with a first reverse osmosis membrane to separate it into a first filtrate and a first concentrate, anda step of neutralizing said first filtrate with an alkali and treating the alkali-neutralized filtrate with a second reverse osmosis membrane to separate it into a second filtrate and a second concentrate,said first concentrate being recycled for said phosphate chemical conversion,said second filtrate being recycled as aqueous wash for said aqueous cleaning, andsaid second concentrate being discarded from the system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.