Removal of chromium from a highly contaminated soil/slag matrix by washing at low pH
- 1 November 1993
- journal article
- research article
- Published by Taylor & Francis in International Journal of Environmental Studies
- Vol. 44 (4), 285-297
- https://doi.org/10.1080/00207239308710868
Abstract
Removal of chromium by soil/slag washing with low pH sulfuric acid solutions and temperature to 95°C is described. The extraction parameters are acid concentration, contact time, temperature, solvent/slag ratio, and acid type. The effect of two‐stage extraction is also discussed. Soil/slag washing with sulfuric acid concentrations of 2% w:v (weight: volume) at 75:1 v:w solvent/slag ratios yielded chromium extraction efficiencies of 95%, but 50% of the matrix was dissolved. Acid washing of soil/slag originally containing 21,000 ppm resulted in residual chromium concentrations of 1,000 ppm or less. Residual chromium is postulated to consist of immobilized chromium fixed to the soil/slag matrix, whereas all surface adsorbed and free chromium is removed. A study on kinetics revealed that extraction at 95°C is completed within five minutes. The effect of temperature is such that chromium removal is significantly improved when extraction is carried out at 95°C rather than at 20°C. At a 75:1 v:w solvent/slag ratio, peak extraction is achieved at a lower concentration than at 25:1 and matrix weight loss is greater. In addition, at 75:1, 95% chromium extraction is achievable, but at 25:1, the maximum chromium removal levels off at 80%. No significant difference is detected in the extractive capabilities of the different mineral acids tested: sulfuric, hydrochloric, and nitric acids. Sulfuric acid is a suitable choice as extractant because of its lower cost and it has other advantages, such as its reduced corrosivity.Keywords
This publication has 7 references indexed in Scilit:
- HANDBOOK OF TOXIC AND HAZARDOUS CHEMICALS AND CARCINOGENS: 1991 — Third EditionPublished by Elsevier ,1992
- Chromium Migration Through Sludge‐Treated SoilsGroundwater, 1986
- Chromium-Bearing Waste Slag: Evaluation of Leachability When Exposed to Simulated Acid PrecipitationPublished by ASTM International ,1984
- Siting of a Metals Industry Landfill on Abandoned Soda Ash Waste BedsPublished by ASTM International ,1984
- Extractable Chromium as Related to Soil pH and Applied ChromiumSoil Science Society of America Journal, 1980
- Behavior of Chromium in Soils: I. Trivalent FormsJournal of Environmental Quality, 1976
- Chromium, Vol. I. Chemistry of Chromium and its CompoundsJournal of the Electrochemical Society, 1956