Foam Delivery of Calcium Polysulfide to Vadose Zone for Chromium-VI Immobilization: A Laboratory Evaluation
The delivery of calcium polysulfide (CPS) to the vadose zone using foam and the immobilization of hexavalent chromium [Cr(VI)] via reduction by the foam-delivered CPS was studied in a series of batch and column experiments. Batch tests were conducted to select the CPS-surfactant foam-generating solutions, to determine the solution foamibility and the reducing potential of CPS-containing foams, and to study the influence of foam quality, surfactant concentration, and CPS concentration on foam stability. Based on the results of the batch experiments, a foaming surfactant-CPS mixture was selected and a system was designed and constructed to generate and deliver foams with high reducing potential and stable enough to be successfully used Cr(VI) immobilization laboratory tests. Column experiments were conducted to test the delivery of the CPS-foam mixtures under conditions similar to field vadose zone, to determine the transport-controlled rate and extent of Cr(VI) immobilization using this novel technology, and to compare the results with those obtained from water-based CPS delivery. Soil reduction was observed in all column tests where CPS was delivered by foam flushing. The massive mobilization of aqueous Cr(VI) which occurred in water-based CPS delivery column experiments was remarkably minimized in the foam-based CPS delivery column experiments, resulting in significant Cr(VI) in-situ immobilization. The results confirmed that foam injection can be successfully used for CPS delivery and Cr(VI) immobilization via reduction in contaminated vadose zones. Due to its advantage over water-based injection, the foam delivery technology can also be for the delivery of other remedial amendments, such as citrate, acetate, and polyphosphate to promote bio-reduction of redox-sensitive contaminants or contaminant precipitation and co-precipitation.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 968201
- Report Number(s):
- PNNL-SA-60896; VZJAAB; TRN: US200924%%334
- Journal Information:
- Vadose Zone Journal, 8(4):976-985, Vol. 8, Issue 4; ISSN 1539-1663
- Country of Publication:
- United States
- Language:
- English
Similar Records
Remediation of Uranium in the Hanford Vadose Zone Using Gas-Transported Reactants: Laboratory Scale Experiments in Support of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau
Foam, a promising vehicle to deliver nanoparticles for vadose zone remediation