Removal of Radioactive Cations and Anions from Polluted Water Using Ligand-Modified Colloid-Enhanced Ultrafiltration

The objectives of this project are to determine the feasibility of and develop optimum conditions for the use of colloid-enhanced ultrafiltration (CEUF) methods to remove and recover radionuclides and associated toxic nonradioactive contaminants from polluted water. The target metal ions are uranium, plutonium, thorium, strontium and lead along with chromium (as chromate). Anionic or amphiphilic chelating agents, used in conjunction with polyelectrolyte colloids, provide a means to confer selectivity required for removal of the target cations. This project entails a comprehensive study of the effects of solution composition and filtration unit operating parameters on the separation efficiency and selectivity of ligand modified colloid-enhanced ultrafiltration (LM-CEUF) processes. Problem areas identified by the Office of Environmental Management addressed by this project include removal of hazardous ionic materials from ground water, mixed waste, and aqueous waste solutions produced during decontamination and decommissioning operations. Separation and concentration of the target ions will result in a substantial reduction in the volume of material requiring disposal or long-term storage

Removal of Radioactive Cations Anions from Polluted Water Using Ligand-Modified Colloid-Enhanced Ultrafiltration (60041-OK)

The objectives of this project are to determine the feasibility of and develop optimum conditions for the use of colloid-enhanced ultrafiltration (CEUF) methods to remove and recover radionuclides and associated toxic non-radioactive contaminants from polluted water. The target metal ions are uranium, plutonium, thorium, strontium, cadmium, and lead along with chromium (as chromate). Anionic or amphiphilic chelating agents, used in conjunction with polyelectrolyte colloids, provide a means to confer selectivity required for removal of the target cations. This project entails a comprehensive study of the effects of solution composition and filtration unit operating parameters on the separation efficiency and selectivity of ligand modified colloid-enhanced ultrafiltration (LM-CEUF) processes. Problem areas identified by the Office of Environmental Management addressed by this project include removal of hazardous ionic materials from ground water, mixed waste, and aqueous waste solutions produced during decontamination and decommissioning operations. Separation and concentration of the target ions will result in a substantial reduction in the volume of material requiring disposal or long-term storage

Surfactant properties of low molecular weight phospholipids

Surface tensions, critical micelle concentrations (CMCs), contact angles on hydrophobic polyethylene, and foaming characteristics of phosphatidic acids, phosphatidylcholines, phosphatidylethanolamines, and phosphatidylglycerols were measured to determine their suitability as substitutes for traditional surfactants. These phospholipids have fatty acid chains of 5 to 12 carbon atoms, a range over which they are soluble at room temperature. Their surface tensions decrease with increasing concentrations until their CMCs are reached, above which their plateau surface tensions are as low as 21 mN/m, indicating excellent surface activities. In general, plateau surface tensions decrease with increasing chain length within each phospholipid type. The classical relationship for In CMC vs. chain length is followed with slopes typical of anionic surfactants for phosphatidic acids and phosphatidylglycerols and resembling zwitterionic surfactants for phosphatidylcholines and phosphatidylethanolamines, consistent with the charge on the hydrophilic group. The wetting capabilities of aqueous solutions on polyethylene are good and foam heights and stabilities are high, the latter two properties being comparable to traditional anionic (sodium dodecylsulfate) and nonionic (octylphenol polyethoxylate) surfactants. Some anomalies are observed regarding the effect of chain length on wetting and foaming, probably due to the depletion effect. Many phospholipids slowly degrade in aqueous solution. We conclude that short-chain phospholipids exhibit excellent surfactant properties and may be useful in many applications.This is a post-print of an article from Journal of Surfactants and Detergents, 8, no. 1 (2005): 65–72, doi: 10.1007/s11743-005-0332-8.</p

Removal of Radioactive Cations and Anions from Polluted Water using Ligand-Modified Colloid-Enhanced Ultrafiltration

The purpose of this project was to develop, optimize, and evaluate new separation methods for removal of hazardous (radionuclides and toxic non-radioactive contaminants) metal ions from either ground water or aqueous waste solutions produced during Decontamination and Decommissioning operations at DOE sites. Separation and concentration of the target ions will result in a substantial reduction in the volume of material requiring disposal or long-term storage. The target metal ions studied were uranium, thorium, lead, cadmium, and mercury along with chromium (as chromate). The methods tested use membrane ultrafiltration in conjunction with water-soluble polymers or surfactants with added metal-selective chelating agents. Laboratory scale tests showed removal of 99.0-99.9% of each metal tested in a single separation stage. The methods developed for selective removal of radionuclides (UO22+, Th4+) and toxic heavy metals (Pb2+, Cd2+, Hg2+) are applicable to two DOE focus areas; decontamination of sites and equipment, and in remediation of contaminated groundwater. Colloid-enhanced ultrafiltration methods have potential to be substantially less expensive than alternative methods and can result in less waste. Results of studies with varying solution composition (concentration, acidity) and filtration parameters (pressure, flow rate) have increased our understanding of the fundamental processes that control the metal ion separation and colloid recovery steps of the overall process. Further laboratory studies are needed to improve the ligand/colloid recovery step and field demonstration of the technology is needed to prove the applicability of the integrated process. A number of graduate students, post-doctoral associates, and research associates have received training and research experience in the areas of separation science, colloid chemistry, and metal ion coordination chemistry of radionuclides and toxic metals. These scientists, some with positions in industry and academia, have the necessary background to address problems related to environmental remediation and. management. The results of this research show the technical feasibility of this separation technique to concentrate radionuclides and toxic metals. The technology developed during this project has wider applications and has been studied for removal of chromate or chlorinated phenolics from industrial wastewater. In several cases, field tests have shown that using colloid-based ultrafiltration is feasible on real-world polluted waters