PBTC•Na₄ (Phosphonobutane-1,2,4-Tricarboxylic Acid Tetrasodium Salt) is a high-performance, environmentally friendly organophosphorus compound widely used in water treatment and industrial applications. Below is a detailed overview of its key properties and primary uses.
I. Key Properties
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Chemical Structure
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Molecular formula: C₇H₇Na₄O₉P
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Combines phosphonate groups (–PO₃H₂) and carboxylate groups (–COOH) in a single molecule, giving it both strong chelating and dispersing capabilities.
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Physical Characteristics
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Appearance: Typically a pale yellow to colorless liquid (or white powder).
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Solubility: Highly soluble in water, easy to handle and dose.
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Thermal & Chemical Stability:
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Stable at high temperatures (up to ≥200 °C).
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Resistant to oxidants (e.g., chlorine, ozone).
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Effective over a broad pH range (generally pH 2–12).
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Functional Properties
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Excellent Scale Inhibition: Particularly effective against calcium carbonate (CaCO₃), calcium sulfate (CaSO₄), barium sulfate (BaSO₄), and—most notably—calcium phosphate [Ca₃(PO₄)₂] scales.
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Corrosion Inhibition: Forms stable complexes with metal ions (e.g., Ca²⁺, Mg²⁺, Fe²⁺), helping to protect metal surfaces.
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Low Phosphorus & Biodegradable: Contains less phosphorus than traditional phosphonates (e.g., HEDP, ATMP) and is readily biodegradable, making it an eco-friendly option.
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Strong Synergistic Effects: Often blended with polymers, zinc salts, or other inhibitors to enhance performance.
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II. Primary Applications
1. Industrial Water Treatment (Core Use)
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Cooling & Circulating Water Systems
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Used as a scale and corrosion inhibitor in recirculating cooling water, especially in high-hardness, high-alkalinity conditions.
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Frequently formulated with dispersant polymers (e.g., polyacrylates, PASP) and corrosion inhibitors (e.g., zinc, tolyltriazole) for synergistic effects.
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Reverse Osmosis (RO) & Desalination Systems
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Serves as an antiscalant to prevent membrane fouling by inorganic salts, improving water recovery and extending membrane life.
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Boiler Water & Steam-Generating Systems
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Effective at high temperatures to inhibit scale formation on heat-exchange surfaces.
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2. Detergents & Cleaning Agents
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Acts as a phosphate-free builder in detergents, providing water softening and anti-redeposition properties.
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Used in industrial cleaning formulations to prevent scale formation during cleaning processes.
3. Oilfield Chemistry
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Applied in water-flooding operations to control scale in injection wells and production equipment, compatible with high-salinity brines.
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Added to acidizing/stimulation fluids to prevent secondary precipitation.
4. Textile, Dyeing & Paper Industries
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Textile: Prevents scale buildup in dyeing machines and steam lines, improving dye uniformity.
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Paper: Controls deposits in white-water systems, reducing equipment scaling.
5. Other Applications
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Metal surface treatment: Stabilizer in electroplating baths and cutting fluids.
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Agriculture: Chelating agent in fertilizer or pesticide formulations.
III. Advantages Over Traditional Alternatives
| Property | PBTC•Na₄ | Conventional Phosphonates (e.g., HEDP) | Polymer Scale Inhibitors (e.g., PAA) |
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| Scale Inhibition | Excellent vs. CaCO₃ & Ca₃(PO₄)₂ | Strong vs. CaCO₃, weaker vs. Ca₃(PO₄)₂ | Good dispersion, weak chelation |
| Oxidant Resistance | Excellent (resists chlorine/ozone) | Poor (easily degraded by oxidants) | Moderate |
| Environmental Profile | Low phosphorus, biodegradable | Higher phosphorus, slower degradation | Non-toxic but often poorly biodegradable |
| pH Range | Broad (2–12) | Mid-alkaline (7–10) | Broad (3–12) |
IV. Handling & Safety Notes
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Dosage: Typically low (1–20 mg/L, depending on water chemistry); lab testing is recommended for optimal dosing.
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Compatibility: Compatible with most water-treatment chemicals, but avoid direct mixing with strong oxidizers or high-valence metal ions (e.g., Al³⁺, Fe³⁺).
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Safety: May cause mild irritation to skin and eyes; use appropriate personal protective equipment (PPE).
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Storage: Store in a cool, dry place; protect liquid products from freezing.
Summary
PBTC•Na₄ is a versatile, phosphonate-carboxylate hybrid water-treatment chemical valued for its:
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Superior scale inhibition (especially against phosphate scales),
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Outstanding thermal and oxidant stability,
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Environmentally friendly profile (low phosphorus, biodegradable).
These properties make it a preferred choice in cooling water systems, RO membrane protection, detergent formulations, and oilfield operations where both high performance and environmental compliance are critical.