SX-EW Pregnant Leach Solution PLS Tank Selection
SX-EW Pregnant Leach Solution (Acidic Copper-Bearing Pregnant Leach Solution at 1-10 g/L Cu and 2-10 g/L H2SO4 Free Acid with Iron, Manganese, Magnesium, Calcium, Aluminum, Cobalt, Nickel, and Chloride Impurity Matrix Recovered from Copper Heap-Leach, Dump-Leach, Tank-Leach, In-Situ-Leach, and Run-of-Mine Leach Pad Operations and Forwarded to Solvent-Extraction Electrowinning Circuit at Morenci, Bagdad, Sierrita, Ray, Mission, Tyrone, Chino, Twin Buttes, Silver Bell, and Latin-American Copper Mine Hydrometallurgy) — Tank Selection at Copper SX-EW Pregnant-Solution Pond, Pregnant-Tank, and Settler Service
SX-EW pregnant leach solution (PLS; acidic copper-bearing pregnant leach solution; CAS not registered as a single substance — matrix of dissolved copper sulfate CuSO4 + sulfuric acid H2SO4 + ferric and ferrous sulfate + manganese sulfate + magnesium sulfate + calcium sulfate + aluminum sulfate + cobalt + nickel + chloride + minor metal impurities recovered from copper-ore heap-leach + dump-leach + tank-leach + in-situ-leach + run-of-mine leach pad operations; typical analysis 1-10 g/L Cu + 2-10 g/L H2SO4 free acid + 0.5-5 g/L Fe + 0.05-2 g/L Mn + 0.5-10 g/L Mg + 0.1-1 g/L Ca + 0.05-1 g/L Cl + 0.1-2 g/L Al + minor Co + Ni + Zn + Mo + Pb + As; pH 1.0-2.5; specific gravity 1.02-1.08; ORP +400 to +600 mV vs Ag/AgCl; temperature 25-50C ambient or solar-warmed; supplied internally to the mine site at 1-50 million-gallon scale collection pond + pregnant tank + raffinate pond + emergency event pond network; PLS chemistry is matrix-dependent on ore mineralogy + leach chemistry + secondary-mineral oxidation + Stage-1 + Stage-2 + Stage-3 leach age) is the dominant intermediate process-solution at modern copper hydrometallurgy SX-EW operations across Arizona (Morenci, Bagdad, Sierrita, Ray, Mission, Silver Bell, Pinto Valley, Mineral Park), New Mexico (Tyrone, Chino, Cobre), Nevada (Robinson, Yerington), Utah (Bingham Canyon), Texas (Asarco), Mexico (La Caridad, Cananea, Buenavista del Cobre), Chile (Escondida, Collahuasi, Spence, Antucoya, Lomas Bayas, Sierra Gorda, Centinela, Mantos Blancos, Mantos de la Luna), Peru (Cerro Verde, Toquepala, Cuajone, Tia Maria), Argentina (Bajo de la Alumbrera, Filo del Sol), and global copper-mining hydromet, providing 80-95% copper recovery + 99.99% Cu cathode product + lower capital and operating cost per pound of copper than smelter-refinery pyrometallurgy at 0.1-1.0% acid-soluble Cu ore.
U.S. Pregnant solution is internal to the mine + never shipped off-site.
The eight sections below cite OSHA Hazard Communication 29 CFR 1910.1200 + 1910.1000 sulfuric-acid PEL + MSHA 30 CFR 56/57 surface-mine acid-mist + EPA Method 6010 + 6020 ICP-OES + ICP-MS metal analytical + EPA Method 9040 pH + EPA Method 8260 + 8270 organic at SX-reagent + EPA NPDES + state-specific mining-discharge permit + EPA SPCC + state-specific copper-bearing process-solution code + EPA RCRA Bevill exemption + Bureau of Land Management Mine Plan of Operations + Forest Service Plan of Operations + State Reclamation Bond + State Aquifer Protection Permit (Arizona ADEQ APP, Nevada NDEP WPCP, New Mexico NMED Discharge Permit, Utah DEQ Groundwater Protection, Mexico SEMARNAT, Chile SMA + RCA, Peru OEFA + ANA) + state mining-permit framework at routine operating practice at North American + Latin-American copper SX-EW operations.
1. Material Compatibility Matrix
SX-EW pregnant leach solution at typical 1-10 g/L Cu + 2-10 g/L H2SO4 + Fe + Mn + Mg + Ca + Al + Cl impurity matrix + pH 1.0-2.5 + 25-50C is a moderately corrosive acidic copper-bearing process solution with acid-corrosion + chloride-stress-corrosion + galvanic-corrosion considerations on metallic construction; HDPE + XLPE + FRP + PP + CPVC + PVC are the dominant polymeric construction materials at PLS service across the leach pad + collection pond + pregnant pond + settler + crud-treatment + raffinate-recycle network. Stainless steel construction is restricted to electrowinning-cell + tankhouse + sampling-station + analytical-lab service at the rectifier-DC-current + acid-mist-control + chloride-aware specification level. Note operating-discipline considerations: chloride-corrosion discipline (chloride above 100 mg/L drives stainless steel pitting + crevice corrosion + AISI 304 + 316 attack at pitting-resistance-equivalent below 35; high-chloride PLS sites — Morenci + Mantos Blancos — require duplex 2205 + 2507 or super-duplex or 6Mo or HC-22 + HC-276 alloy at electrowinning-cell + sampling station), acid-mist discipline (electrowinning-cell evolves H2SO4 acid mist at 5-25 mg/m3 above the cell; OSHA PEL-TWA 1 mg/m3 + ACGIH TLV-TWA 0.2 mg/m3 acid-mist; cell-house ventilation + acid-mist suppressant FOAM cover or bead-cover + acid-mist scrubber + supplied-air-respirator at sampling work is mandatory), copper-zinc-iron contamination discipline (SX reagent loaded organic phase rejects iron + manganese + chloride to raffinate; raffinate iron buildup drives jarosite + ferric-hydroxide precipitation at neutralization step; PLS impurity budget management is routine), and crud accumulation discipline (PLS solid + organic crud accumulates at SX-settler interface + drives organic loss + reduced extraction; crud treatment via clay-tower + filter + centrifuge is routine SX operating practice).
| Material | SX-EW PLS @ 25C | SX-EW PLS @ 50C | Notes |
|---|---|---|---|
| HDPE rotomolded | A | A | Standard at PLS + raffinate + reagent + sample + adjacency service across the 1,500-10,000-gallon range; opaque-pigmented for UV protection |
| XLPE rotomolded | A | A | Standard at higher-temperature solar-warmed PLS service |
| Polypropylene (PP) | A | A | Standard at smaller acid-resistance specialty service |
| FRP vinyl-ester resin | A | A | Standard at larger PLS bulk + settler-feed service across the 50,000-2,000,000-gallon scale |
| FRP polyester resin | B | C | Acceptable at lower-acid PLS only; not preferred at high-acid hot service |
| 304 stainless steel | C | NR | NOT recommended at PLS service due to acid + chloride attack; pitting + stress-corrosion-cracking risk |
| 316L stainless steel | C | NR | NOT recommended at high-chloride PLS site; acceptable at low-chloride sample-station only |
| Duplex 2205 / 2507 | B | B | Acceptable at higher-chloride PLS sample-station + analytical-lab service |
| Super-duplex / 6Mo / HC-22 | A | A | Premium at electrowinning-cell + tankhouse busbar + high-chloride site |
| Carbon steel uncoated | NR | NR | NOT recommended; rapid acid corrosion + iron-contamination of PLS |
| Carbon steel rubber-lined | A | A | Standard at primary settler + crud-treatment vessel at PLS service; natural rubber or chlorobutyl liner |
| Lead-lined steel | A | A | Standard at electrowinning-cell construction; chemical lead 99.99% Pb-Sb 6% antimony alloy |
| EPDM | A | A | Standard gasket + lining + pond geomembrane support material at PLS service |
| Viton (FKM) | A | A | Standard at higher-temperature electrowinning + settler pump + valve seat |
| HDPE 60-mil + 80-mil geomembrane liner | A | A | STANDARD at copper-leach pad + PLS pond + raffinate pond + event pond primary + secondary liner |
| PVC Sch 80 | A | B | Standard at piping at PLS service to 50C; temperature-derated above 50C |
| CPVC Sch 80 | A | A | Preferred at higher-temperature PLS piping |
The dominant industrial pattern at North American + Latin-American copper SX-EW operations is HDPE 60-mil or 80-mil double-liner pond at copper-leach pad + PLS pond + raffinate pond + event pond, FRP vinyl-ester resin or rubber-lined carbon-steel construction at the larger 50,000-2,000,000-gallon PLS pregnant tank + settler-feed + crud-treatment vessel, and HDPE rotomolded tank at the 1,500-10,000-gallon process-water + reagent makedown + sample + analytical-lab + adjacency service. Lead-lined steel at electrowinning-cell + super-duplex or HC-22 alloy at high-chloride site are pyrometallurgy-grade specifications outside HDPE 5-brand scope. OneSource Plastics' 5-brand HDPE network (Norwesco, Snyder Industries, Chem-Tainer, Enduraplas, Bushman) covers the typical 1,500-10,000-gallon copper-mine PLS + raffinate + reagent + sample + adjacency specification across the standard hydromet envelope; primary 50,000-2,000,000-gallon PLS settler-feed + pregnant-tank + crud-treatment + raffinate-collection vessel typically calls FRP vinyl-ester or rubber-lined carbon-steel construction outside our HDPE 5-brand scope; we refer those specifications to qualified FRP + lined-steel tank fabricators.
2. Real-World Industrial Use Cases
Copper Heap-Leach and Dump-Leach Mining (Dominant Use). Copper hydromet operations crush oxide + secondary-sulfide ore at 0.1-1.0% acid-soluble Cu to 0.5-2 inch P80, agglomerate at 5-15 kg/t H2SO4, stack at 20-100-foot lift on HDPE 60-mil or 80-mil double-liner pad with leak-detection + collection sump, and drip-irrigate at 0.005-0.015 gpm/ft2 with raffinate at 1-5 g/L H2SO4 + recycled iron + chloride for 60-365-day leach cycle. Pregnant solution drains by gravity to PLS pond + pregnant tank + SX settler-feed circuit. Storage envelope: HDPE 60-mil + 80-mil double-liner pond at 5-100 million-gallon scale; FRP vinyl-ester or rubber-lined carbon-steel pregnant tank + settler-feed at 50,000-2,000,000-gallon scale; HDPE rotomolded tank at the process-water + reagent + sample + adjacency 1,500-10,000-gallon scale.
SX-EW Solvent Extraction and Electrowinning Tankhouse. SX-EW circuit extracts copper from PLS into kerosene + LIX-class oxime extractant at extraction-train (1-3 stages countercurrent) + back-extracts copper from organic into spent-electrolyte at strip-train (1-2 stages countercurrent) + electrowins copper at lead-anode + stainless-blank cathode in tankhouse at 1.8-2.2 V cell-voltage + 220-380 A/m2 current-density + 35-50C temperature + 35-50 g/L Cu + 150-180 g/L H2SO4 electrolyte. Storage envelope: lead-lined-steel + super-duplex or HC-22 electrowinning cell + FRP or rubber-lined-steel rich-organic + lean-organic + spent-electrolyte + pregnant-electrolyte tank typically OUTSIDE HDPE scope; HDPE rotomolded reagent + sample + analytical-lab tank at adjacency service.
In-Situ Leach (ISL) Copper Mining. Florence Copper + Excelsior Gunnison + Taseko Florence-style in-situ leach injects sulfuric-acid leach solution into permeable copper-bearing aquifer + recovers PLS via production well to surface SX-EW circuit. Storage envelope: HDPE rotomolded process-water + reagent + sample tank at 1,500-10,000-gallon scale + FRP vinyl-ester or rubber-lined carbon-steel PLS pregnant tank + settler-feed.
Tank-Leach and Concentrate-Leach Operations. Specialty copper tank-leach at high-grade oxide ore + concentrate-leach at copper-arsenic refractory concentrate uses agitated tank with sulfuric-acid + pressure-oxidation autoclave + ferric-iron oxidant. Storage envelope: pressure-rated stainless or titanium autoclave OUTSIDE HDPE scope.
Sulfuric Acid + Reagent Adjacency. Sulfuric-acid + LIX-class extractant + isoparaffinic-kerosene diluent + flocculant + dispersant + emulsifier + lime + makeup chemistry + sample + analytical-lab adjacency at the heap-leach + SX-EW + tankhouse circuit uses HDPE rotomolded 1,500-10,000-gallon storage in the standard mining 5-brand network, with sulfuric-acid bulk storage at 5,000-25,000-gallon FRP vinyl-ester typically outside HDPE scope.
3. Regulatory Framework
OSHA 29 CFR 1910.1200 + 1910.1000 Sulfuric Acid PEL. Sulfuric acid + acid-mist OSHA PEL-TWA 1 mg/m3 + ACGIH TLV-TWA 0.2 mg/m3 + IDLH 15 mg/m3. PLS at 2-10 g/L H2SO4 dilute matrix is classified Skin Irritant Cat 2 + Eye Irritant Cat 2 at GHS framework + worker SDS + container labeling + PPE + emergency-shower-eye-wash discipline.
MSHA 30 CFR 56/57 Surface-Mine Acid-Mist Standard. MSHA 30 CFR 56.5001 + 57.5001 acid-mist air-contaminant 1 mg/m3 + supplied-air-respirator at electrowinning-cell + tankhouse + acid-makedown + sampling work.
EPA Method 6010 + 6020 ICP-OES + ICP-MS Metal Analytical. EPA SW-846 Method 6010 + 6020 + 7470 + 7471 + 200.7 + 200.8 metal analytical for Cu + Fe + Mn + Mg + Ca + Al + Pb + As + Cd + Cr + Ni + Co + Hg + Zn at PLS + raffinate + groundwater + outfall + tailings sample collection.
EPA NPDES + State Mining Discharge Permit. Copper-bearing PLS + raffinate + tailings discharge to surface water requires state-specific mining-discharge permit + NPDES outfall + tailings-impoundment + reclamation-bond framework. State-specific aquifer-protection permit (Arizona ADEQ APP, Nevada NDEP WPCP, New Mexico NMED Discharge Permit, Utah DEQ Groundwater Protection) requires double-liner + leak-detection + groundwater monitoring well + closure-plan + reclamation-bond.
EPA SPCC + State Copper-Bearing Process-Solution Code. Copper-bearing PLS + raffinate solution storage requires double-liner + leak-detection + secondary-containment per state-specific process-solution code; pregnant-pond + raffinate-pond + event-pond + stormwater-pond inventory + closure-plan.
Bureau of Land Management + Forest Service + State Mining Permit. Federal-land copper hydromet operations require BLM Mine Plan of Operations + Forest Service Plan of Operations + state mining permit + reclamation bond + closure-plan + financial-assurance framework. State-specific reclamation bond is mandatory at Arizona AAC R11-13 + Nevada NAC 519A + New Mexico NMED MMD + Utah Mining Reclamation Plan + 1872 General Mining Law framework.
EPA RCRA Subtitle C Bevill Exemption. Copper-mine ore + tailings + PLS + raffinate generally qualify for Bevill exemption to RCRA Subtitle C under 40 CFR 261.4(b)(7) at most heap-leach + SX-EW operations. Spent SX organic + crud + electrowinning sludge + tankhouse spent-electrolyte may be subject to characteristic hazardous waste classification at site-specific evaluation.
EPCRA + TRI Reporting. Copper-mine TRI-reporting threshold per EPCRA 313 + 40 CFR 372 covers Cu + Pb + As + Cd + Cr + Ni + Hg + Zn + sulfuric acid releases at the mine-site SX-EW + tankhouse + tailings facility annual reporting framework.
4. Storage System Specification
Heap-Leach Pad and PLS Pond HDPE Geomembrane Liner. Copper heap-leach pad + PLS pond + raffinate pond + event pond + stormwater pond uses HDPE 60-mil or 80-mil double-liner construction with primary + secondary liner separated by geonet drainage layer + leak-detection sump + GCL or compacted-clay subliner per state-specific aquifer-protection permit. Liner installation by qualified geomembrane installer with electric leak-detection survey at acceptance per ASTM D7007. Heap-pad solution distribution piping is HDPE SDR 11 or SDR 17 with drip-emitter at the standard 0.005-0.015 gpm/ft2 application rate.
PLS Pregnant Tank and Settler-Feed Vessel (Outside HDPE Scope). Primary PLS pregnant tank + SX settler-feed + crud-treatment vessel at 50,000-2,000,000-gallon scale uses FRP vinyl-ester resin construction or rubber-lined carbon-steel construction with natural-rubber or chlorobutyl-rubber liner. Construction at qualified FRP or lined-steel tank fabricator with NDE inspection + holiday-test on liner. This specification is OUTSIDE OneSource Plastics' HDPE 5-brand scope; we refer those specifications to qualified FRP + lined-steel tank fabricators.
Process Water and Reagent Makedown Tank (HDPE Scope). Process-water + sulfuric-acid-makedown + lime-makedown + flocculant-makedown + emulsifier-makedown + LIX-reagent-storage + sample + analytical-lab adjacency at the mine site 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.
SX Mixer-Settler and Crud-Treatment. SX mixer-settler vessel at 50,000-500,000-gallon scale uses FRP vinyl-ester resin or rubber-lined carbon-steel construction with EPDM or chlorobutyl gasket + 304 + 316L stainless-steel mixer impeller + ceramic-or-rubber-coated baffle. Crud-treatment vessel + clay-tower + filter + centrifuge at the SX-organic-recovery circuit uses FRP or stainless construction outside HDPE scope.
Electrowinning Cell and Tankhouse. Lead-lined steel + super-duplex 2507 or HC-22 alloy + chemical-lead 99.99% Pb-Sb 6% antimony cell construction with anode-busbar + cathode-blank + acid-mist suppressant FOAM cover or bead cover + acid-mist scrubber. This specification is OUTSIDE OneSource Plastics' HDPE 5-brand scope.
Containment and Spill Pad. All copper-bearing PLS + raffinate + electrolyte storage requires secondary containment per EPA SPCC + state-specific aquifer-protection permit; concrete-bermed pad with HDPE primary + secondary liner + leak-detection sump + acid-resistant epoxy or polyurea topcoat.
5. Field Handling Reality
Handler PPE. Copper-mine PLS handling: chemical-resistant Tyvek or equivalent suit at any open-system PLS work, double nitrile chemical-resistant glove at any contact, chemical splash goggles + face shield at any open-system handling, supplied-air respirator at electrowinning-cell + tankhouse + acid-makedown work above OSHA acid-mist PEL, half-mask air-purifying respirator with acid-gas-cartridge at routine open-system work, steel-toe boots with chemical-resistant overshoe, eye-wash station + emergency shower per OSHA 29 CFR 1910.151 within 10 seconds of work area, designated-trained acid-area worker per OSHA 29 CFR 1910.1450 + MSHA Part 46 + Part 48 framework.
Acid-Mist Discipline at Electrowinning Cell. Electrowinning-cell evolves H2SO4 acid mist at 5-25 mg/m3 above the cell from oxygen-evolution at lead anode + spray-droplet from current-density work. Cell-house ventilation at 50-200 air-changes-per-hour + acid-mist suppressant FOAM cover or HDPE bead-cover or expanded-PE bead cover at every cell + acid-mist scrubber at the cell-house exhaust + supplied-air-respirator at sampling + cell-cleaning + cathode-stripping work is mandatory.
Chloride-Corrosion Discipline at Stainless Steel. Chloride above 100 mg/L in PLS drives stainless-steel pitting + crevice + stress-corrosion-cracking at sample-station + analytical-lab + electrowinning-cell. Site chloride budget management via raffinate iron precipitation + bleed-stream + ion-exchange treatment is routine; high-chloride site (Mantos Blancos + chloride-leach Antofagasta) calls super-duplex 2507 or HC-22 + HC-276 alloy at affected component.
Crud Accumulation Discipline. SX mixer-settler interface accumulates organic + solid crud at typical 0.5-3% by volume of organic phase; crud is treated at clay-tower + filter + centrifuge to recover entrained organic + reduce organic-loss + maintain extraction-stage efficiency. Routine crud-treatment cycle at 7-30-day frequency.
Raffinate Recycle and Iron Buildup. Raffinate at 1-5 g/L H2SO4 + 1-5 g/L Fe + minor metal recycles to heap-pad makeup. Iron buildup at the raffinate cycle drives jarosite + ferric-hydroxide precipitation at downstream neutralization + lime-makedown step. Iron precipitation discipline + raffinate iron-budget management is routine.
Cargo-Tank Receipt of Sulfuric Acid and Reagent. Sulfuric-acid bulk receipt at 5,000-25,000-gallon FRP vinyl-ester storage + LIX-class reagent receipt at 250-330-gallon poly tote + isoparaffinic-kerosene diluent receipt at 5,000-15,000-gallon UL-142 carbon-steel storage. PPE + transfer-rate-monitoring + secondary-containment + emergency-deluge framework.
QC Sampling and Verification. Each PLS + raffinate + pregnant-electrolyte + spent-electrolyte sample collection: Cu + Fe + Mn + Mg + Ca + Al + Cl + acid + impurity per EPA Method 6010 + 6020 ICP, pH continuous + grab confirmation, ORP, conductivity, density, organic-entrainment by phase-disengagement test, crud-content by gravimetric.
Spill Response. PLS + raffinate spill response: small-volume spill is contained at secondary-containment + neutralized in place with lime + sodium-hydroxide to pH 8-10 + transferred via vacuum-truck to event-pond. Large-volume spill triggers state-agency notification + downstream water-quality sampling + remediation per state aquifer-protection permit.
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