EVALUATION OF A METHOD USING COLLOIDAL GAS APHRONS TO REMEDIATE METALS-CONTAMINATED MINE DRAINAGE WATERS
Experiments were conducted in which three selected metals-contaminated mine drainage water samples were treated by chemical precipitation followed by flotation using colloidal gas aphrons (CGAs) to concentrate the precipitates. Drainage water samples used in the experiments were collected from an abandoned turn-of-the-century copper mine in south-central Wyoming, an inactive gold mine in Colorado's historic Clear Creek mining district, and a relatively modern gold mine near Rapid City, South Dakota. The copper mine drainage sample was nearly neutral (pH 6.5) while the two gold mine samples were quite acidic (pH {approx}2.5). Metals concentrations ranged from a few mg/L for the copper mine drainage to several thousand mg/L for the sample from South Dakota. CGAs are emulsions of micrometer-sized soap bubbles generated in a surfactant solution. In flotation processes the CGA microbubbles provide a huge interfacial surface area and cause minimal turbulence as they rise through the liquid. CGA flotation can provide an inexpensive alternative to dissolved air flotation (DAF). The CGA bubbles are similar in size to the bubbles typical of DAF. However, CGAs are generated at ambient pressure, eliminating the need for compressors and thus reducing energy, capital, and maintenance costs associated with DAF systems. The experiments involved precipitation of dissolved metals as either hydroxides or sulfides followed by flotation. The CGAs were prepared using a number of different surfactants. Chemical precipitation followed by CGA flotation reduced contaminant metals concentrations by more than 90% for the copper mine drainage and the Colorado gold mine drainage. Contaminant metals were concentrated into a filterable sludge, representing less than 10% of the original volume. CGA flotation of the highly contaminated drainage sample from South Dakota was ineffective. All of the various surfactants used in this study generated a large sludge volume and none provided a significant concentration factor with this sample. For the two samples where CGA flotation was effective, the separation was very rapid and the concentrate volume was reduced when compared to gravity separation under similar conditions. Effective separations were achieved with very low chemical dosages and low residence times, suggesting the possibility of economic viability for processes based on this concept. The CGA flotation experiments described in the following report were conducted to provide preliminary data with which to assess the technical feasibility of using the method for remediation of metals-contaminated mine drainage waters. The experiments were conducted using common, low-cost, precipitating reagents and CGA prepared from several surfactants. Results were evaluated in terms of metals concentration reduction, reagent consumption, and concentrate volume. The results of these preliminary experiments indicate that CGA flotation may be a useful tool for the treatment of some types of mine drainage.
- Research Organization:
- Western Research Institute (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FC26-98FT40322
- OSTI ID:
- 822153
- Resource Relation:
- Other Information: PBD: 1 Jun 2002
- Country of Publication:
- United States
- Language:
- English
Similar Records
Technique for harvesting unicellular algae using colloidal gas aphrons. [Chlorella vulgaris]
Evaluation of a subsurface oxygenation technique using colloidal gas aphron injections into packed column reactors