{
    "title": "Ligand-assisted supercritical fluid extraction for the removal of transuranic contamination",
    "inventor_name": "Chien M. Wai",
    "publication_year": 2008,
    "device_name": "Ligand-assisted supercritical fluid extraction system",
    "goal": "Recover uranium and other transuranic metals from radioactive ash and contaminated soils.",
    "problem_addressed": "Radioactive waste containing transuranic contamination (ash, incinerator residues, soils).",
    "concept_summary": "A supercritical carbon-dioxide (CO_2) extraction process in which a chemical ligand is added to bind uranium, plutonium and other metals. The supercritical CO_2 carries the metal-ligand complexes out of the waste matrix; pressure reduction releases the metals, and the ligand/solvent can be recycled.",
    "detailed_description": "The process uses supercritical CO_2 (~=6.9 MPa, 31  deg C) as a green solvent. A ligand (complexing agent) that selectively binds actinides is mixed with the waste (incinerator ash or contaminated soil). The supercritical CO_2 flows through the waste, dissolving the ligand-metal complexes. After extraction, the CO_2 is depressurized to a gas, leaving the metal-ligand complexes behind. A counter-current stripping column with a stripping agent separates the metal from the ligand, allowing the ligand and CO_2 to be recycled. The method has been demonstrated on 32 t of ash at Richland, WA, and in laboratory soil tests achieving up to 80 % plutonium extraction.",
    "category": "Chemistry & Chemical Processes",
    "principles": [
        "Supercritical fluid extraction",
        "Ligand complexation of actinides",
        "Counter-current stripping",
        "Pressure-induced solvent recovery"
    ],
    "scientific_domains": [
        "Chemistry",
        "Chemical Engineering",
        "Nuclear Engineering",
        "Environmental Science"
    ],
    "mechanisms_of_action": [
        "Supercritical CO_2 dissolves ligand-metal complexes",
        "Ligand selectively binds uranium, plutonium, etc.",
        "Pressure drop releases metals from the solvent",
        "Stripping agent separates metals from ligand"
    ],
    "materials": [
        "Carbon dioxide (CO_2)",
        "Ligands / complexing agents",
        "Oxidizing agents",
        "Acid/base reagents",
        "Uranium-containing ash",
        "Plutonium-spiked soil"
    ],
    "energy_sources": [
        "Heat (to reach supercritical temperature)",
        "Electricity (for pumps and compressors)"
    ],
    "inputs": [
        "Incinerator ash or contaminated soil",
        "Supercritical CO_2",
        "Ligand solution",
        "Oxidizing/complexing agents"
    ],
    "outputs": [
        "Recovered uranium",
        "Recovered plutonium",
        "Depleted ash/soil",
        "Spent ligand (to be regenerated)"
    ],
    "claimed_performance": "Plutonium extraction efficiencies 14-19 % in first run, 60-80 % after parameter adjustment; recovery of ~2 t of uranium from 32 t of ash (~=$6 M value).",
    "experimental_evidence": "Laboratory soil extractions showed up to 80 % plutonium removal; pilot-scale plant planned to process 32 t of ash at Richland, WA; first industrial demonstration announced in 2008.",
    "replication_status": "First full-scale demonstration planned with AREVA on 32 t of ash; no independent replication reported.",
    "keywords": [
        "supercritical fluid extraction",
        "CO_2",
        "ligand assistedation",
        "uranium recovery",
        "radioactive waste",
        "transuranic contamination",
        "green chemistry"
    ],
    "related_technologies": [
        "Solvent extraction",
        "Metal chelation",
        "Nuclear fuel recycling",
        "Incinerator ash processing"
    ],
    "controversy_level": "low",
    "confidence_score": 0.9,
    "practicability_score": 0.8,
    "fringe_score": 0.2,
    "evidence_strength": 0.7,
    "risk_score": 0.2,
    "trl_estimate": 6,
    "source_urls": [
        "http://www.sciencedaily.com/releases/2008/08/080821213606.htm",
        "http://nextbigfuture.com/2008/08/french-process-to-extract-uranium-from.html",
        "http://www.osti.gov/energycitations/servlets/purl/769006-JTCMFJ/webviewable/769006.pdf"
    ],
    "organizations": [
        "University of Idaho",
        "AREVA",
        "Idaho Research Foundation"
    ],
    "applications": [
        "Nuclear fuel recycling",
        "Radioactive waste remediation",
        "Material recovery from incinerator ash"
    ],
    "limitations": [
        "Requires high-pressure equipment",
        "Ligand synthesis and recovery costs",
        "Regulatory approvals for handling actinides",
        "Scalability to large waste streams"
    ],
    "open_questions": [
        "Long-term environmental impact of the ligand-CO_2 process",
        "Economic viability at commercial scale",
        "Efficiency of ligand regeneration",
        "Compatibility with different waste matrices"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "The process has been extremely collaborative ... the technology is simple, cost-effective and environmentally friendly.",
        "Supercritical carbon dioxide has directly dissolved and removed caffeine from whole coffee beans for decades.",
        "After a second round wherein the initial extraction parameters were changed, the plutonium extraction efficiencies increased to 60 % and as high as 80 %...",
        "AREVA is eager to test its first full-scale use on 32 tons of incinerator ash in Richland, Wash.",
        "The new recycling plant is expected to be operational in 2009 and will take about a year to process AREVA's ash inventory."
    ]
}