Sodium Diethyl Dithiocarbamate (SDDC) Storage — Polymetallic Sulfide Flotation + Heavy-Metal Wastewater Treatment
Sodium Diethyl Dithiocarbamate (SDDC, NaDDC) Storage — C5H10NNaS2 Selective Collector for Sulfide Flotation, Heavy-Metal Wastewater Treatment, and Polymetallic Concentrator Tank Selection
Sodium diethyl dithiocarbamate (SDDC, NaDDC, sodium N,N-diethylcarbamodithioate, C5H10NNaS2, CAS 148-18-5) is a salt of diethyldithiocarbamic acid; the sodium-cation form ionizes to the diethyldithiocarbamate anion (C2H5)2NCSS- in aqueous solution. The chemistry is a selective sulfide-mineral flotation collector with broader application across heavy-metal-cation chelation chemistry: industrial uses include (1) selective copper / lead / zinc / antimony / silver / mercury sulfide-mineral flotation collector at polymetallic concentrators with lower dose-per-ton than xanthate or dithiophosphate collectors, (2) heavy-metal wastewater treatment precipitation reagent (HMTA, heavy-metal-treatment agent) for industrial-effluent + smelter-water + battery-recycling-water + electroplating-rinse-water + groundwater-remediation chemistry, (3) rubber vulcanization accelerator + secondary accelerator (the diethyldithiocarbamate-zinc complex Zinc Diethyldithiocarbamate, ZDEC, is a workhorse rubber-vulcanization accelerator), (4) analytical-chemistry reagent for trace-metal photometric determination + atomic-absorption-sample-preparation chelation extraction.
Commercial product is white to pale-yellow crystalline solid + flake hydrate (typically as the trihydrate Na(C2H5)2NCS2·3H2O); molecular weight 171.26 g/mol anhydrous + 225.31 g/mol trihydrate; specific gravity 1.10-1.20 g/cm3; water solubility highly soluble (typical 35-45 g/100 g water at 25°C); aqueous solution pH 8-10 (mildly basic); decomposes at temperatures above 50-60°C in aqueous solution to dimethylamine + carbon disulfide CS2 + sulfur-containing degradation products.
The chemistry's flotation function in mining is selective collector activity for noble-metal + secondary-copper + lead + zinc + antimony sulfide minerals via N-C-S-Cu (or N-C-S-Pb / N-C-S-Zn / N-C-S-Sb) bidentate chelate-coordination chemistry on the mineral surface. Compared to xanthate, SDDC offers: (1) lower dose per ton ore (10-50 g/t versus 30-200 g/t for xanthate at typical applications) due to higher specific collecting power per gram, (2) slightly better selectivity to noble-metal sulfide vs pyrite + pyrrhotite gangue, (3) compatible with polymetallic Cu-Pb-Zn-Ag separation circuits where xanthate selectivity is insufficient, (4) handles in solid + dry product form similar to xanthate but with less self-heating + spontaneous-combustion concern (no Class 4.2 spontaneously-combustible solid classification).
Typical mining industrial dosing rates run 5-50 g per metric ton of ore as primary or co-primary collector or 5-20 g/t as secondary supplement to xanthate. The chemistry is dosed as 5-15% aqueous solution prepared at the concentrator point-of-use through dry-product feed-hopper + makedown-vessel mixing.
1. Material Compatibility Matrix
SDDC dry product is non-corrosive crystalline salt; aqueous solution at 5-15% is mildly basic pH 8-10 + moderately reducing + contains trace CS2 from low-temperature solution decomposition. Material selection prioritizes mild-base resistance + sulfide-corrosion control + UV protection.
| Material | SDDC dry product | 5-15% aqueous solution | Notes |
|---|---|---|---|
| HDPE / XLPE | A | A | Standard for solution makedown + day-tank storage; 1.0 SG sufficient (solution density approximately 1.05-1.10 g/cm3) |
| Polypropylene | A | A | Standard for fittings, pump bodies, mixer impellers |
| FRP vinyl ester | A | A | Standard for outdoor bulk solution storage; UV-stabilized gel coat needed |
| FRP isophthalic polyester | B | B | Acceptable; vinyl ester preferred for sulfide service |
| PVC / CPVC | A | A | Standard for solution-feed piping |
| 304 / 316L stainless | A | A | Standard for makedown vessel construction |
| Carbon steel | B | B | Acceptable short-term; long-term sulfide + alkali corrosion drives epoxy lining |
| Aluminum | NR | NR | Alkali attack; never in solution service |
| Copper / brass / bronze | NR | NR | Diethyldithiocarbamate-Cu chelate complex + corrosion + collector consumption |
| EPDM | A | A | Standard gasket selection |
| Viton (FKM) | A | A | Premium for severe-service rotating equipment seals |
| Buna-N (Nitrile) | A | A | Standard for general-purpose gasket service |
| Natural rubber | B | B | Acceptable; modest swelling + mild alkali degradation |
The dominant industrial pattern at mining concentrators is HDPE rotomolded vertical solution-makedown + day-tank installation in the 500-10,000 gallon range with 304L or 316L stainless makedown-vessel + paddle agitator + dust-collected solids feed-hopper above. Heavy-metal wastewater-treatment installations (electroplating + battery-recycling + smelter + groundwater-remediation industrial sites) typically run smaller-scale 100-2,000 gallon HDPE solution-makedown + dosing-skid configurations.
2. Real-World Industrial Use Cases
Polymetallic Sulfide Concentrators (Cu-Pb-Zn-Sb-Ag-Au Selective Recovery). The chemistry's primary mining application is at complex-mineralogy polymetallic concentrators where xanthate selectivity is insufficient. Operations at Cannington (Australia; Pb-Ag primary + Cu-Zn polymetallic), Mount Isa (Cu-Pb-Zn polymetallic), Red Dog (Alaska; Pb-Zn polymetallic with Ag content), Tara (Ireland; Pb-Zn), Antamina (Peru; Cu-Zn polymetallic), Penasquito (Mexico; Pb-Zn-Au-Ag polymetallic), Tizapa (Mexico), Naica (Mexico), Buenaventura Uchucchacua (Peru; Pb-Ag polymetallic), Volcan (Peru), San Cristobal (Bolivia; Pb-Zn-Ag), Bolivar (Bolivia), and Rasp (Australia; Pb-Zn) deploy SDDC at 5-30 g/t ore as selective collector for sequential Cu / Pb / Zn / Sb / Ag / Au mineral separation. The chemistry's tighter selectivity than xanthate enables higher concentrate-grade differentiation between adjacent metal stages in polymetallic flotation circuits.
Antimony-Sulfide Concentrators (Stibnite Selective Collection). Antimony-primary + antimony-byproduct operations at Hillgrove (Australia; primary antimony at Costerfield + Hillgrove), Murchison (Australia), Sunshine (Idaho USA; legacy primary silver + antimony), Ozkar Stibnite (Idaho), Wuxi + Lengshuijiang (China; the world's largest antimony producers), and Tajikistan + Russia + Bolivia + Mexico + Turkey antimony operations use SDDC at 30-100 g/t ore for selective stibnite (Sb2S3) recovery. The chemistry's antimony-mineral collecting power is one of the strongest commercial collector options for stibnite-flotation metallurgy.
Mercury-Cinnabar Concentrators (Legacy + Specialty). Mercury-cinnabar (HgS) flotation at legacy + specialty Hg operations historically used SDDC for selective cinnabar collection. The chemistry's mercury-mineral collecting power is documented but the broader Hg-mining industry has contracted dramatically since the 1990s due to environmental regulation; current applications are limited to specialty + recycle + remediation operations.
Heavy-Metal Wastewater Treatment (Industrial Effluent Precipitation). The chemistry's chelation chemistry with heavy-metal cations (Cu2+, Pb2+, Zn2+, Cd2+, Ni2+, Hg2+, Cr3+, As3+/5+, Sb3+/5+) makes SDDC a workhorse heavy-metal-precipitation reagent (HMTA, heavy-metal-treatment agent) for industrial-effluent treatment. Major application areas: (1) electroplating + metal-finishing industry rinse-water + spent-bath-water treatment per 40 CFR Part 433 Metal Finishing Effluent Guidelines, (2) battery-recycling industry (lead-acid + lithium-ion + nickel-cadmium recycling) wastewater treatment, (3) smelter + refinery + mineral-processing wastewater + tailings-decant treatment, (4) groundwater remediation at former mining + industrial sites, (5) electronic-circuit-board manufacturing rinse-water treatment, (6) printed-circuit-board recycling + WEEE-recycling water treatment. Typical application is 10-1,000 mg/L SDDC dose to wastewater followed by sedimentation + filtration to remove the metal-DDC chelate precipitate; the technology achieves heavy-metal residual concentrations in treated water below 0.01 mg/L for most metals at appropriate dose + pH conditions.
Rubber Industry Vulcanization (Zinc Diethyldithiocarbamate, ZDEC). The zinc salt of diethyldithiocarbamate (ZDEC, zinc diethyldithiocarbamate, CAS 14324-55-1) is a workhorse rubber-vulcanization secondary accelerator used in: latex foam manufacturing, gloves + condoms + medical-device latex products, tire compounds (limited use due to nitrosamine formation concerns), industrial rubber goods. ZDEC is manufactured from SDDC + zinc-sulfate or zinc-chloride aqueous reaction with subsequent precipitation + filtration. Major ZDEC producers + consumers operate captive SDDC-to-ZDEC manufacturing chemistry alongside flotation-collector + wastewater-treatment SDDC supply.
Analytical Chemistry Reagent. SDDC + diethyldithiocarbamate-class chelating reagents are workhorse analytical reagents for trace-metal photometric determination + atomic-absorption-sample-preparation chelation extraction at environmental + industrial-hygiene + clinical laboratories. Reagent-grade SDDC at $50-500 per kg pricing is a small-volume but technically-important product class.
3. Regulatory Hazard Communication
OSHA, NIOSH, ACGIH Exposure Limits. SDDC is not specifically OSHA PEL or NIOSH REL or ACGIH TLV listed; the chemistry's intermediate-toxicity + low vapor pressure + moderate dermal absorption profile drives the absence from formal exposure-limit lists. The decomposition product CS2 (carbon disulfide; OSHA PEL 20 ppm 8-hr TWA + 30 ppm ceiling per 29 CFR 1910.1000 Table Z-2; NIOSH REL 1 ppm 8-hr TWA + 10 ppm STEL with skin notation) is the primary regulated airborne exposure at solution-makedown + day-tank operations where warm-temperature solution decomposition occurs.
OSHA HazCom GHS Classification. SDDC commercial product per supplier SDS typically carries: H302 Harmful if Swallowed Category 4; H315 Causes Skin Irritation Category 2; H319 Causes Serious Eye Irritation Category 2A; H335 May Cause Respiratory Irritation Category 3; H400 Very Toxic to Aquatic Life Category 1; H410 Very Toxic to Aquatic Life with Long-Lasting Effects Category 1.
NFPA 704 Diamond. SDDC dry product rates NFPA Health 2 (acute oral toxicity Cat 4; skin + eye + respiratory irritant Cat 2-3; aquatic toxicity Cat 1), Flammability 1 (combustible at high temperature; not flammable at typical handling conditions), Instability 1 (decomposition with heat + acid releases CS2 + amine + sulfide degradation products), no special hazard.
DOT and Shipping. SDDC dry product ships under varying UN designations depending on specific product + commercial concentration: UN 3077 (Environmentally Hazardous Substance, Solid, n.o.s.) Hazard Class 9 PG III for the aquatic-toxicity profile is common, or non-regulated for some lower-hazard formulations. Verify per supplier product label + SDS. Bulk shipping: rail covered hopper car, dry-bulk pneumatic tank truck, ISO container, 1,000 kg supersack, or 25 kg multilayer paper bag.
EPA TSCA, NPDES, RCRA. SDDC (CAS 148-18-5) is on EPA TSCA Active Inventory. The chemistry is not a SARA TRI Section 313 listed chemical, not CWA 311 hazardous substance, and not Clean Air Act Hazardous Air Pollutant. Concentrator NPDES discharge limits at 40 CFR Part 440 Ore Mining and Dressing Point Source Category may include SDDC residual + total-organic-carbon contribution at concentrator effluent points; site-specific permit conditions vary. The chemistry's biodegradability is moderate-to-fast (the dithiocarbamate backbone is biodegradable on weeks-months timescale at typical tailings + reclaim-water conditions).
Heavy-Metal Wastewater Treatment Compliance. SDDC heavy-metal-treatment-reagent applications support compliance with 40 CFR Part 433 Metal Finishing Effluent Guidelines + 40 CFR Part 413 Electroplating Effluent Guidelines + state-level industrial-wastewater discharge permits + federal RCRA characteristic + listed-waste cleanup standards under 40 CFR Part 261 (D004-D043 toxicity characteristic). Treatment-residual disposal: the heavy-metal-DDC chelate precipitate is typically RCRA-non-hazardous solid waste at properly-treated effluent conditions but specific characterization per state environmental permit + sample analysis is required.
4. Storage System Specification
Dry Product Storage (Mining Concentrator + Industrial Wastewater Treatment). Plant-scale operations maintain 30-90 days of SDDC dry-product inventory in: (1) 25 kg multilayer paper-laminate bags within 1,000 kg supersack outer wrapping, OR pelletized + briquetted product in 1,000 kg supersack, OR bulk silo storage at very-large operations. Storage area design: closed warehouse with low humidity + temperature control (target under 30°C ambient + relative humidity under 60%; SDDC trihydrate is hygroscopic + absorbs additional moisture which causes caking + handling difficulty), sealed-bag inventory with FIFO rotation, segregation from acids + oxidizers + ignition sources per IFC Chapter 50.
Solution Makedown Station (Mining Concentrator). Captive on-site solution preparation is the dominant industrial pattern. Configuration: (1) bag-loading hopper above 2,000-10,000 gallon HDPE or stainless makedown vessel, dust-collection ducting to baghouse for fugitive dust during bag-tip, (2) makedown vessel with paddle or top-entry agitator (3-10 minute mixing time at ambient temperature for full SDDC dissolution), (3) finished-solution transfer pump + day-tank holding (typical day-tank turnover 24-48 hours; fresh batch made up daily; warmer + UV-exposed solution accelerates CS2-evolving decomposition), (4) automated metering pumps from day-tank to flotation-cell distribution.
Heavy-Metal Wastewater Treatment Dosing Skid. Smaller wastewater-treatment installations (electroplating, battery-recycling, groundwater-remediation, smelter-water-treatment) use 100-2,000 gallon HDPE solution-makedown + diaphragm metering pump + flow-controlled dosing into the wastewater treatment system. Solution preparation typically 5-15% SDDC concentration; wastewater dose 10-1,000 mg/L SDDC depending on heavy-metal load + treatment-target residual.
Day-Tank Storage. 100-1,000 gallon HDPE day tanks with PVC piping + PP fittings + EPDM gaskets, HDPE secondary containment pan sized 110% of tank volume, level instrumentation + low-level alarm, vent to outdoor stack or activated-carbon filter for CS2 + amine vapor management.
Outdoor Tank Considerations. Outdoor solution storage at concentrators + industrial sites: UV-stabilized HDPE or FRP vinyl-ester construction, freeze-protection heat-tracing + insulation in cold climates (SDDC solution freezes near 0°C), shade canopy or reflective coating reduces UV degradation + accelerated decomposition, secondary containment dike sized 110% of largest tank volume per 40 CFR 112 SPCC.
5. Field Handling Reality
CS2 Decomposition Vapor Control. SDDC aqueous solution at warm + acidic + UV-exposed conditions decomposes to release CS2 (carbon disulfide) + diethylamine + sulfide degradation products. CS2 is highly flammable (NFPA 30B Class IB extremely-flammable + IDLH 500 ppm + reproductive-tox Hazard) + occupational-exposure-relevant at concentrator + treatment-plant operations. Engineering controls: (1) closed-tank construction with vent-to-stack or activated-carbon-filter vapor control, (2) cool + dark + alkaline solution storage (the CS2 decomposition kinetics accelerate at warm + acidic conditions; pH buffering at pH 9-10 with mild caustic soda dose extends solution stability significantly), (3) downwind community-relations program at operations near population centers.
Bag-Tip Dust Control. The dominant occupational hazard for SDDC handling is dust exposure during bag-tip + supersack-discharge into makedown-vessel hoppers. Engineering controls: closed bag-tip hopper with local exhaust ventilation to dust-collection baghouse, Class II Division 2 dust-rated electrical equipment within hopper + 5-foot radius. Workers at the bag-tip station require chemical-resistant gloves, safety goggles + face shield, NIOSH P100 + organic-vapor cartridge respirator, chemical-resistant overalls.
Acid-Reactivity and Storage Compatibility. SDDC must be segregated from: strong acids (rapid decomposition + CS2 evolution + thermal release; HCl + H2SO4 + HNO3 + acetic acid all incompatible), strong oxidizers (chlorine, hypochlorite, peroxide, nitric acid; potential explosive interaction or fire), copper + brass + bronze fittings + tools (DDC-Cu chelate complex + corrosion + collector consumption). Compatible storage with most other concentrator chemistries (xanthate solution + dry, frothers, lime, sodium silicate, sodium hydrosulfide stored separately by physical form + acid-base segregation).
Spill Response. SDDC spill response: (1) dry product spill: vacuum or sweep into containers for re-use or non-hazardous waste disposal; minimize water contact (mixing dry SDDC with water creates a fluid solution that can drain to storm or sanitary sewer); (2) aqueous solution spill: confine + contain with absorbent boom + earth dike, prevent storm-drain or process-water-circuit ingress (SDDC is highly aquatic-toxic with H400 Cat 1 classification), recover free liquid to drum or vacuum truck for re-use, absorb residual liquid with vermiculite or clay-based absorbent + dispose as non-hazardous industrial waste subject to state environmental permit (or as RCRA hazardous waste if heavy-metal contamination from upstream service drives the characterization).
Solution Stability and Day-Tank Turnover. SDDC aqueous solution at pH 9-10 + cool + dark conditions has multi-day stability with slow decomposition; solution at pH below 7 + warm + UV-exposed conditions decomposes within hours. Operating discipline: 24-48 hour day-tank turnover, alkaline-buffered solution preparation, sealed-tank storage, indoor or shaded outdoor tank installation.
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