Rare-Earth Oxalate Precipitation Tank Selection

Rare-Earth Oxalate Precipitation Process Solution (REE2(C2O4)3 Group-REE Oxalate Precipitate Slurry at pH 1-2 Generated by Oxalic Acid (COOH)2 Addition to REE Chloride or REE Nitrate Feed Solution at 60-80 C Stoichiometric Plus 5-15% Excess Forming 0.5-2.0 M REE Oxalate White Crystalline Filterable Solid as Group-REE Purification and Calcination Precursor at MP Materials, Lynas LAMP, Solvay La Rochelle, Iridium Bayan Obo, Energy Fuels White Mesa, IREL Manavalakurichi, and Shenghe Jiangxi Refinery Operations) — Process-Water and Adjacency Tank Selection at REE Oxalate Precipitation

Rare-earth oxalate precipitation process solution (mixed REE2(C2O4)3 group-REE oxalate trihydrate precipitate slurry generated at pH 1-2 by stoichiometric-plus-5-to-15-percent-excess oxalic-acid (COOH)2 addition to REE chloride REECl3 or REE nitrate REE(NO3)3 feed solution at 0.5-2.0 M total REE concentration + 60-80 C in agitated reactor with 1-4 hour aging time; produces white crystalline filterable solid REE2(C2O4)3 (REE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) at greater-than-99.5% yield + greater-than-99.99% group purity post-recrystallization; subsequent vacuum-drum + horizontal-belt + plate-and-frame filtration + de-watering at 50-65 wt% solid + calcination at 800-1100 C in oxygen-bearing atmosphere produces final REE2O3 oxide product) is the dominant intermediate-purification + final-product step at U.S. + Australian + European + Indian + Chinese REE-refinery operations including MP Materials Mountain Pass California + Lynas LAMP Kuantan Malaysia + Solvay La Rochelle France + Iridium Bayan Obo China + Energy Fuels White Mesa Utah + IREL Manavalakurichi India + Shenghe Resources Jiangxi China + Vital Metals Saskatoon Canada. The mother-liquor at less-than-0.05 M residual REE + free oxalic acid + chloride or nitrate is recycled or treated as oxalate-bearing wastewater requiring oxalate destruction prior to discharge under EPA NPDES + state-specific refinery-discharge permit.

U.S. + Australian + European + Indian + Chinese rare-earth-element oxalate-precipitation supply is concentrated at major operators (MP Materials Mountain Pass California Stage-1-LREE-and-Stage-2-NdPr restart + Lynas Rare Earths LAMP Kuantan Malaysia separation-and-precipitation + Solvay La Rochelle France integrated separation + Iridium Bayan Obo Inner Mongolia integrated cracking-and-separation + Energy Fuels White Mesa Utah cracking + IREL Manavalakurichi India + Shenghe Jiangxi China + Vital Metals Saskatoon Canada). Bulk oxalic-acid + soda-ash + caustic-soda + ammonium-bicarbonate adjacency reagent supply at the precipitation facility is conventional industrial-chemical procurement.

The eight sections below cite OSHA Hazard Communication 29 CFR 1910.1200 + 1910.1000 oxalic-acid + radioactive-aerosol air-contaminant ceiling + IAEA NORM-TENORM + 10 CFR 20 NRC source-material license + 40 CFR 192 EPA UMTRCA + ASTM D511 Cl + ASTM D1971 metals + EPA Method 6010 + 6020 + 9056 ICP-AES + ICP-MS REE + sulfate analytical + EPA NPDES + state-specific refinery-discharge permit + EPA SPCC + state-specific NORM-TENORM tailings code + EPA RCRA Subtitle C + Bevill exemption + DOE NDAA Sec 154 critical-mineral source + Defense Production Act Title III rare-earth + Defense Logistics Agency Strategic and Critical Stockpile + EXIM Bank financing framework at routine operating practice at North American + Australian + European + Indian + Chinese REE-refinery operations.

1. Material Compatibility Matrix

Rare-earth oxalate precipitation process solution at typical pH 1-2 acidic + 0.5-2.0 M REE chloride or nitrate + free oxalic acid + 60-80 C operating temperature is a moderately corrosive acidic chloride or nitrate solution with manageable corrosion envelope against polymeric construction at the working-strength specification. Operating-discipline controls: temperature discipline (60-80 C operating range at precipitation reactor accelerates oxalic-acid + chloride attack on 304 + 316L stainless above 60 C; FRP vinyl-ester + PVDF + HDPE-lined-steel preferred at higher-temperature service), free-acid-strength discipline (pH 1-2 free acid is moderate; HDPE acceptable at less-than-2 N at ambient; FRP vinyl-ester acceptable at higher concentration + temperature), NORM-TENORM radiation discipline (Th + U residual at less-than-0.1 ppm post-cracking-and-separation; oxalate-precipitate-cake at REE separation step is essentially radiation-clean; mother-liquor may carry trace activity), and crystal-habit + filtration discipline (REE-oxalate crystal habit + particle-size depends on temperature + agitation + supersaturation + aging time + impurity profile; precipitation reactor design is critical for downstream filtration + cake-washing + de-watering performance).

The dominant industrial pattern at U.S. + Australian + European + Indian + Chinese REE-refinery operations is FRP vinyl-ester resin construction at 5,000-200,000-gallon scale for primary REE oxalate precipitation reactor + storage tank, HDPE-lined carbon-steel + PVDF-lined-steel at 50,000-500,000-gallon scale for premium-purity precipitation containment, glass-lined-steel at the high-purity individual-REE oxalate precipitation step, and HDPE rotomolded tanks at the process-water + oxalic-acid-makedown + soda-ash-makedown + caustic-makedown + flocculant + reagent + analytical-lab + adjacency 1,500-10,000-gallon scale outside the primary precipitation circuit. OneSource Plastics' 5-brand HDPE network (Norwesco, Snyder Industries, Chem-Tainer, Enduraplas, Bushman) covers the process-water + oxalic-acid-makedown + soda-ash-makedown + caustic-makedown + flocculant + reagent adjacency envelope at REE refinery operations; primary precipitation reactor + storage at 5,000-500,000-gallon scale requires FRP vinyl-ester or PVDF-lined-steel or HDPE-lined-steel or glass-lined-steel construction OUTSIDE our HDPE 5-brand scope, and we refer those specifications to qualified FRP vinyl-ester + PVDF + HDPE-lining + glass-lining tank fabricators.

2. Real-World Industrial Use Cases

Group-REE Oxalate Precipitation Post-SX (Dominant Use). Group-REE chloride or nitrate solution at 0.5-2.0 M total REE post-solvent-extraction is precipitated as group-REE oxalate at pH 1-2 with stoichiometric-plus-5-to-15-percent-excess oxalic-acid at 60-80 C in agitated reactor with 1-4 hour aging time. White crystalline filterable solid REE2(C2O4)3.10H2O is filtered + washed + dried + calcined at 800-1100 C to final REE2O3 oxide product. Storage envelope: 5,000-200,000-gallon FRP vinyl-ester or HDPE-lined-steel precipitation reactor.

Individual-REE Oxalate Precipitation Final-Purification. Individual high-purity Nd + Pr + Sm + Eu + Gd + Tb + Dy + Y + La + Ce solution at greater-than-99.99% post-multistage-SX is precipitated as individual-REE oxalate at the same pH 1-2 + oxalic-acid stoichiometry + 60-80 C process. Glass-lined-steel reactor preferred for premium-purity service. Storage envelope: 5,000-50,000-gallon glass-lined-steel + FRP vinyl-ester precipitation reactor.

Filtration and De-Watering Step. Vacuum-drum + horizontal-belt + plate-and-frame filtration + de-watering of REE-oxalate-precipitate to 50-65 wt% solid uses HDPE-lined or FRP vinyl-ester filtrate-collection tank at 5,000-100,000-gallon scale; mother-liquor recycled to upstream process or treated as oxalate-bearing wastewater. Storage envelope: 5,000-100,000-gallon FRP vinyl-ester or HDPE-lined-steel filtrate tank.

Calcination Feed and Roasted-Oxide Product. De-watered REE-oxalate cake feed to rotary-kiln or fluidized-bed calciner at 800-1100 C in oxygen-bearing atmosphere produces REE2O3 oxide final product. Calcination dust collection + scrubber-makedown + caustic-scrubber + lime-scrubber adjacency at HDPE 5-brand 1,500-10,000-gallon scale.

Process Water and Reagent Adjacency. Process water + oxalic-acid-makedown + soda-ash-makedown + caustic-makedown + ammonium-bicarbonate-makedown + flocculant + reagent adjacency at the precipitation facility uses HDPE rotomolded 1,500-10,000-gallon storage in the standard chemical-process 5-brand network.

3. Regulatory Framework

OSHA 29 CFR 1910.1200 + 1910.1000 + 1910.1450 Hazard Communication. Oxalic-acid + soda-ash + caustic-soda + ammonium-bicarbonate handling at REE-refinery precipitation requires OSHA Hazard Communication SDS + container labeling + PPE specification (chemical splash goggles + face shield + chemical splash suit + chemical-resistant glove + steel-toe boots + air-purifying respirator with oxalic-acid + caustic-aerosol cartridge + eye-wash + emergency shower per 1910.151 within 10 seconds of work area + designated trained operator + radiation-area-worker dosimetry framework at TENORM-impacted area).

IAEA NORM-TENORM and 10 CFR 20 NRC Source Material License. Group-REE oxalate-precipitate at less-than-0.1 ppm Th + less-than-0.05 ppm U post-cracking-and-separation is essentially radiation-clean; mother-liquor + recycle stream may carry trace activity under 10 CFR 20 NRC source-material license framework + 40 CFR 192 UMTRCA + state-specific radiation-control-program. Operator dose-rate survey + ALARA program + dosimetry at TENORM-impacted-area worker is mandatory.

EPA RCRA Subtitle C + Bevill Exemption. REE-precipitation residue + mother-liquor + filtrate classify based on residual REE + oxalate + Th + U content; Bevill exemption applies to mining-extracted ore + tailings under 40 CFR 261.4(b)(7); but oxalate-bearing wastewater + sludge may require state-specific RCRA characterization.

EPA Method 6010 + 6020 ICP-AES + ICP-MS REE Analytical. EPA SW-846 Method 6010C ICP-AES + 6020B ICP-MS at every NPDES + RCRA + state radiation-control compliance sample for total-REE quantification + Th + U + Ra-226 + Pb-210 + radium-equivalent activity-concentration. ASTM D1971 metals analytical framework. Oxalate by ion chromatography or titration.

EPA NPDES + State Refinery-Discharge Permit. REE-refinery precipitation discharge to surface water requires state-specific refinery-discharge permit + EPA NPDES outfall + oxalate-destruction-pretreatment + radiation-monitoring + reclamation-bond framework at every operating REE refinery.

EPA SPCC + State NORM-TENORM Tailings Code. REE precipitation reactor + filtrate + mother-liquor storage requires double-liner + leak-detection + secondary-containment + radiation-shielded-containment per state-specific NORM-TENORM tailings + radioactive-source-material code at TENORM-impacted facility.

Oxalate Destruction Pretreatment. Mother-liquor + filtrate oxalate-bearing wastewater requires oxalate-destruction at thermal + biological + chemical-oxidation step prior to discharge per state-specific refinery-discharge permit; permanganate + ozone + biological-degradation are dominant treatment options.

DOE NDAA Sec 154 Critical-Mineral Source and Defense Production Act Title III. Rare earth elements are designated critical mineral; U.S. DOD Industrial Base + DLA Strategic and Critical Stockpile + EXIM Bank financing + DOE Rare Earth Demonstration Plant Wheat Ridge Colorado provides domestic-REE-precipitation support framework.

4. Storage System Specification

Primary REE Oxalate Precipitation Reactor and Tank (OUTSIDE OneSource HDPE Scope). Primary REE oxalate precipitation reactor + storage tank at 5,000-500,000-gallon scale uses FRP vinyl-ester resin construction with C-veil chemical-resistant interior corrosion-barrier + structural-laminate + UV-resistant exterior gel-coat per ASTM D3299 + D4097 specification, or HDPE-lined carbon-steel construction with 250-mil rotational-molded HDPE liner + secondary-containment + leak-detection per state code, or PVDF-lined or glass-lined-steel construction at higher-purity service. This specification is OUTSIDE OneSource Plastics' HDPE 5-brand scope; we refer those specifications to qualified FRP vinyl-ester + PVDF + HDPE-lining + glass-lining tank fabricators.

Process Water and Reagent-Makedown Tank (HDPE Scope). Process-water + oxalic-acid-makedown + soda-ash-makedown + caustic-makedown + ammonium-bicarbonate-makedown + flocculant-makedown + reagent makedown at the precipitation facility uses 1,500-10,000-gallon HDPE or XLPE rotomolded vertical flat-bottom or shallow-cone-bottom atmospheric tank, 1.85 specific-gravity rated, mounted on level reinforced-concrete pad with secondary containment via integral catch-basin or external concrete-bermed pad sized to 110% of largest-tank volume; 3-4 inch flanged top fill + atmospheric vent; 2-3 inch flanged bottom outlet with full-bore PVC ball valve; 18-24 inch top manway; ultrasonic level transmitter; sample valve; opaque-pigmented HDPE for UV protection at outdoor service; freeze-protection insulation + heat-trace at northern-state operation.

Filtrate and Mother-Liquor Tank (Mixed Scope). Filtrate + mother-liquor recycle at 5,000-100,000-gallon scale uses FRP vinyl-ester or HDPE-lined-steel construction at primary mother-liquor service, with HDPE 5-brand scope at adjacent scrubber + reagent-makedown adjacency 1,500-10,000-gallon service.

Radiation-Area Containment. All precipitation reactor + filtrate + mother-liquor storage at TENORM-impacted area requires radiation-shielded secondary containment + leak-detection + double-liner + concrete-bermed-pad with epoxy or polyurea topcoat + dose-rate monitoring + final-status-survey at decommissioning per 10 CFR 20 + 40 CFR 192 + state-specific radiation-control-program.

Containment and Spill Pad. All precipitation + filtrate + mother-liquor storage requires secondary containment per EPA SPCC + state-specific NORM-TENORM tailings + chemical-storage code; concrete-bermed pad with HDPE primary + secondary liner + leak-detection sump + acid-resistant epoxy or polyurea topcoat + radiation-survey at access.

5. Field Handling Reality

Handler PPE. REE-precipitation-area entry: full-face supplied-air or air-purifying respirator with oxalic-acid + caustic-aerosol cartridge for routine open-system handling, chemical splash suit + chemical-resistant apron at any open-system handling, double nitrile or neoprene chemical-resistant glove at any contact, chemical splash goggles + face shield, steel-toe boots with chemical-resistant overshoe, eye-wash + emergency shower per OSHA 29 CFR 1910.151 within 10 seconds of work area, dosimetry-badge framework at TENORM-impacted-area worker, designated trained-operator + ALARA-program oversight at every TENORM-impacted task.

Crystal-Habit Discipline. REE-oxalate crystal habit + particle-size depends on temperature 60-80 C + agitation 1-3 W/L mixer-power + supersaturation 1.5-3.0 + aging time 1-4 hour + impurity profile; precipitation reactor design with proper agitator + baffles + temperature control is critical for downstream filtration + cake-washing + de-watering performance. Continuous online crystal-habit + particle-size measurement at premium-purity production.

Acid-Spill Response. Acidic precipitation slurry spill response: small-volume spill is contained at secondary-containment + neutralized in place with soda-ash or lime + sampled to less-than-0.5 N free acid + transferred via vacuum-truck to event-pond or process recycle. Large-volume spill triggers state-agency notification + radiation-survey + downstream water-quality + dose-rate sampling.

Cargo-Tank Receipt and Reagent Off-Loading. Oxalic-acid + soda-ash + caustic-soda + ammonium-bicarbonate bulk delivery: tanker pre-transfer site-survey + chemical-suit + air-purifying-respirator + Buddy-system + transfer-rate-monitoring + leak-detection + emergency-deluge per OSHA 1910.120 HAZWOPER. Oxalic-acid is typically dry solid or saturated solution delivery.

Process-Water Impurity Management. Cl + SO4 + PO4 + NO3 + alkali + Ca + Mg + Ba + Sr cation impurity in REE-feed solution drives REE-oxalate co-precipitation selectivity + impurity-budget management; raw-water + recycled-water analysis at quarterly frequency with ICP-MS metal-impurity budget management is routine.

QC Sampling and Verification. Each precipitation-reactor + filtrate + mother-liquor + cake sample collection: total-REE per ICP-MS + ICP-AES + individual REE distribution per ICP-MS at every step + free-oxalate per ion chromatography or titration + free-acid per acid-base titration + Th + U + Ra-226 per gamma-spec at TENORM-impacted-stream + pH continuous + grab confirmation + specific-gravity + temperature continuous + crystal-habit + particle-size at premium-purity production.

Scale and Sludge Management. REE-oxalate fines + Ba-Sr-Ca-oxalate co-precipitation + Ra-bearing-scale accumulates at tank surface + filter cake + transfer pipeline; routine 30-90-day inspection + descaling + radiation-survey + scale-disposal as TENORM waste under state radiation-control-program is required.

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