Method for treating soil contaminated with heavy metals
US5967965A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 29, 1997 |
| Grant date | Oct 19, 1999 |
| Priority date | — |
| Expiry date | Aug 29, 2017 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S210/913
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
Abstract
A method for treating heavy metal contaminated soils, particularly those containing hexavalent chromium, which includes a first soil washing at pH 9-12 with an anionic synthetic organic flocculant followed by a liquid-solid phase separation such as by gravity separation including sedimentation, an optional second soil sludge washing at pH 2.5-3.0 with addition of a metal valency reducing agent which when done is followed by a second liquid-solid phase separation using a cationic synthetic organic flocculant, combining the first and second stage liquids and optional treating the liquid phase with a metal valency reduction agent such as sodium metabisulfite under acidic conditions followed by treatment with an alkaline agent to form insoluble metal hydroxide which is separated in a phase separation process and is combined with the final sludge, recycling the liquid from washing stage or stages for use in soil processing, dewatering the separated sludge or sludges using a separation method (e.g. pressure filtration, centrifuge, etc.) and treating the dewatered sludge with an alkaline reagent, such as dry lime dust, lime slurry, potassium or sodium hydroxide thus resulting in metal imm…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.