Isolation of Metals from Liquid Wastes: Reactive in Turbulent Thermal Reactors

Technical Report · Sun Sep 30 00:00:00 EDT 2001

DOI:https://doi.org/10.2172/829931· OSTI ID:829931

Wendt, Jost O.L.

A Generic Technology for treatment of DOE Metal-Bearing Liquid Waste The DOE metal-bearing liquid waste inventory is large and diverse, both with respect to the metals (heavy metals, transuranics, radionuclides) themselves, and the nature of the other species (annions, organics, etc.) present. Separation and concentration of metals is of interest from the standpoint of reducing the volume of waste that will require special treatment or isolation, as well as, potentially, from the standpoint of returning some materials to commerce by recycling. The variety of metal-bearing liquid waste in the DOE complex is so great that it is unlikely that any one process (or class of processes) will be suitable for all material. However, processes capable of dealing with a wide variety of wastes will have major advantages in terms of process development, capital, and operating costs, as well as in environmental and safety permitting. Moreover, to the extent that a process operates well with a variety of metal-bearing liquid feedwastes, its performance is likely to be relatively robust with respect to the inevitable composition variations in each waste feed. One such class of processes involves high-temperature treatment of atomized liquid waste to promote reactive capture of volatile metallic species on collectible particulate substrates injected downstream of a flame zone. Compared to low-temperature processes that remove metals from the original liquid phase by extraction, precipitation, ion exchange, etc., some of the attractive features of high-temperature reactive scavenging are: The organic constituents of some metal-bearing liquid wastes (in particular, some low-level mixed wastes) must be treated thermally in order to meet the requirements of the Resource Conservation and Recovery Act (RCRA) and Toxic Substances Control Act (TSCA), and the laws of various states. No species need be added to an already complex liquid system. This is especially important in light of the fact that DOE has already experienced problems with organic complexants added to precipitate radionuclides. For example, the Defense Nuclear Facilities Safety Board has expressed, in a formal Recommendation to the Secretary of Energy, its concern about the evolution of benzene vapor in concentrations greater then the lower flammability limit from tanks to which sodium tetraphenylborate has been added to precipitate 137Cs in the ''In-Tank Precipitation'' (ITP) process at the Savannah River Site. Other species added to the waste in the ITP process are sodium titanate (to adsorb 90Sr and Pu), and oxalic acid. Avoiding addition of organics to radioactive waste has the additional advantage that is likely to significantly reduce the rate of radiolytic and radiolytically-induced hydrogen generation (c.f. Meisel et al., [1993]), in which it is shown that removal of organics reduces the rate of hydrogen generation in simulated waste from Hanford tank 241-SY-101 by over 70%. Organic species already present are destroyed with very high efficiency. This attribute is especially attractive with respect to high-level tank waste at the Hanford Site, in which large amounts of citrate, glyoxylate, EDTA (ethylenediaminetetraacetic acid), and HEDTA [N-(2- hydroxyethyl)-ethylenediaminetriacetic acid] were added to precipitate radionuclides. These organic species are important in the thermal and radiolytic generation of methane, hydrogen, and nitrous oxide, flammable mixtures of which are episodically vented from 25 tanks on Hanford's Flammable Gas Watch List [Hopkins, 1994]. The same basic approach can be used to treat a broad range of liquid wastes, in each case concentrating the metals (regardless of liquid-phase oxidation state or association with chelators or absorbents) using a collectible sorbent, and destroying any organic species present. In common with the Army's approach (see section 2.2) to the thermal destruction of a 10 range of chemical warfare agents (GB, VX, and two blister agents), this may drastically simplify process and plant design and facility permitting, and reduce capital costs, by avoiding development of a separate ''wet'' process for each type of liquid waste source. The expected robustness of the process with respect to gross feedwaste composition suggests a relatively high degree of tolerance with respect to inevitable variations in the composition of a given metal-bearing feedwaste. For these reasons, high-temperature reactive scavenging is a potentially attractive approach to the removal of metals from liquid waste in the DOE complex. 2.2. Community Acceptability of High-Temperature Waste Processing

• Research Organization: University of Arizona, Tucson, AZ (US)
• Sponsoring Organization: USDOE Office of Environmental Management (EM) (US)
• DOE Contract Number: A107-97ER14839; FG07-97ER14837; FG07-97ER14831
• OSTI ID: 829931
• Report Number(s): EMSP-60326; R&D Project: EMSP 60326; TRN: US0404816
• Resource Relation: Other Information: PBD: 30 Sep 2001
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
29 ENERGY PLANNING
POLICY AND ECONOMY
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
54 ENVIRONMENTAL SCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CAPITALIZED COST
CHEMICAL WARFARE AGENTS
ION EXCHANGE
LIQUID WASTES
NITROUS OXIDE
NUCLEAR FACILITIES
OPERATING COST
OXALIC ACID
RADIOACTIVE WASTES
RADIOISOTOPES
RESOURCE CONSERVATION
THERMAL REACTORS
TOXIC SUBSTANCES CONTROL ACTS
TRADE
VALENCE
WASTE PROCESSING
WASTES