Potassium Persulfate, Potassium Peroxydisulfate, Dipotassium Peroxodisulfate, Potassium Monopersulfate, E922, 7727-21-1

Potassium Persulfate, Potassium Peroxydisulfate, Dipotassium Peroxodisulfate, Potassium Monopersulfate, E922, 7727-21-1

POTASSIUM PERSULFATE (K₂O₈S₂, E922)

1. Chemical Identity and Material Classification

• Chemical Name: Potassium Peroxydisulfate

• Synonyms: Potassium Persulfate, Potassium Peroxodisulfate, Dipotassium Peroxodisulfate, Dipotassium Peroxydisulfate, Potassium monopersulfate, Dipotassium Disulfate, Peroxydisulfuric Acid Dipotassium Salt

• CAS Number: 7727-21-1

• EC Number (EINECS): 231-781-8

• Molecular Formula: K₂O₈S₂ (also written as K₂S₂O₈)

• Molecular Weight: 270.33 g/mol

• E Number: E922 (food additive – not widely approved, restricted)

• Chemical Class: Inorganic persulfate, strong oxidizing agent, radical initiator

• HS Code: 2833.40

• UN Number: 1492 (Potassium persulfate, 5.1, PG III)

2. Physical Properties

2.1 General Physical Properties

2.2 Solubility Properties

2.3 Particle Characterization

2.4 Hygroscopicity and Stability

3. Chemical Properties

3.1 Molecular Structure

• Structure: K⁺ [O₃S–O–O–SO₃]²⁻ K⁺

• Bond type: Ionic (K⁺) + covalent peroxy bridge (–O–O–)

• Peroxy group: Contains one peroxy bond (–O–O–) – source of oxidizing and radical-initiation activity

• Active oxygen content: ~5.9% (theoretical)

• Potassium content: ~28.9% (by weight)

• Sulfur content: ~23.7% (by weight)

3.2 Thermal Properties

3.3 Chemical Reactivity

3.4 Electrochemical Properties

3.5 Radical Formation Mechanism (Polymerization Initiator)

4. Commercial Grades and Specifications

5. Quality Specifications (Technical/Industrial Grade)

6. Production Methods

6.1 Electrochemical Method (Most Common – Industrial Scale)

• Reaction (electrochemical oxidation of potassium sulfate): 2 K₂SO₄ + 2 H₂SO₄ → K₂S₂O₈ + 2 KHSO₄ + 2 H₂

• Process:

  1. Concentrated potassium sulfate (K₂SO₄) and sulfuric acid (H₂SO₄) solution is prepared

  2. Solution is electrolyzed in a platinum or lead dioxide anode cell

  3. At the anode: 2 SO₄²⁻ → S₂O₈²⁻ + 2 e⁻

  4. At the cathode: 2 H⁺ + 2 e⁻ → H₂ (hydrogen gas evolved)

  5. Potassium persulfate crystallizes from the solution

  6. Crystals are filtered, washed, and dried

• Yield: 85–95%

• Purity: 98–99%

• Advantage: High purity, no organic residues

• Note: This is the same method used for ammonium and sodium persulfate production.

6.2 Chemical Oxidation Method (Less Common)

• Reaction (oxidation of potassium sulfate with ozone or hydrogen peroxide): 2 K₂SO₄ + H₂O₂ + H₂SO₄ → K₂S₂O₈ + 2 KHSO₄ + 2 H₂O (not commercially efficient)

• Process: Not economically viable; primarily of academic interest.

6.3 Purification from By-product Streams

• Potassium persulfate can be obtained as a by-product from the production of ammonium persulfate via metathesis, but this is not common.

7. Mechanism of Action (Functional Mechanisms)

7.1 Polymerization Initiator Mechanism (Most Important Application ~70%)

• Step 1 – Thermal or UV activation: S₂O₈²⁻ → 2 SO₄·⁻ (sulfate radical anion)

• Step 2 – Radical addition to monomer: SO₄·⁻ + CH₂=CHX → ·CH₂–CHX–SO₄⁻ (monomer radical)

• Step 3 – Chain propagation: Monomer radical reacts with additional monomers → polymer chain growth

• Step 4 – Termination: Radicals combine or disproportionate → polymer chain ends

• Typical monomers polymerized:

  • Styrene → polystyrene (latex)

  • Butadiene + styrene → styrene-butadiene rubber (SBR)

  • Acrylonitrile + butadiene + styrene → ABS

  • Acrylates (methyl methacrylate, ethyl acrylate) → acrylic polymers

  • Vinyl acetate → polyvinyl acetate (PVAc)

  • Vinyl chloride → polyvinyl chloride (PVC – suspension polymerization)

  • Acrylamide → polyacrylamide (flocculant)

7.2 Oxidizing Agent Mechanism (General)

• Aqueous reduction: S₂O₈²⁻ + 2 e⁻ → 2 SO₄²⁻

• Applications:

  • Etching/corrosion: Oxidizes metal surfaces (copper, zinc) → metal sulfates

  • Desizing (textiles): Oxidizes starch-based sizing agents → soluble products

  • Bleaching (hair, cosmetics): Oxidizes melanin pigments → color removal

  • Wastewater treatment: Oxidizes organic pollutants, cyanides, phenols

  • Swimming pool shock treatment: Oxidizes chloramines, organic contaminants

7.3 Gel Breaker Mechanism (Oil & Gas – Hydraulic Fracturing)

• Problem: Fracturing fluids (guar gum, hydroxypropyl guar) form viscous gels

• Action: Persulfate decomposes thermally (downhole temperature ~50–120°C) to form SO₄·⁻ radicals

• Radical reaction: Radicals attack polymer backbone (guar gum) → chain scission

• Result: Viscosity reduction → fluid flows back to surface (fracture fluid recovery)

• Controlled release: Encapsulated persulfate (coated) for delayed breaker action

7.4 Oxidation of Chloramines (Pool/Spa Treatment)

• Reaction with chloramines (NH₂Cl, NHCl₂): S₂O₈²⁻ + NH₂Cl → N₂ + Cl⁻ + 2 SO₄²⁻ + H₂O

• Result: Eliminates chlorine odor, reduces eye/skin irritation

• Note: Potassium monopersulfate (KHSO₅) is more commonly used for pool shock treatment; potassium persulfate is less common.

7.5 Food Additive Mechanism (E922 – Restricted)

• Flour treatment: Oxidizes glutathione (reducing agent) in flour → strengthens gluten

• Result: Improved dough handling, increased bread volume, better crumb structure

• Regulatory status: Not approved in EU (banned); approved in some other countries with restrictions (Japan, Brazil)

8. Applications

8.1 Polymerization Initiator – Largest Application (~70%)

Typical polymer products:

• SBR (Styrene-Butadiene Rubber): Tires, conveyor belts, footwear

• Acrylic polymers: Paints, adhesives, coatings, acrylic glass (PMMA)

• PVC (Polyvinyl Chloride): Pipes, profiles, cables, flooring

• Polyacrylamide: Water treatment flocculant, enhanced oil recovery

• Superabsorbent polymers: Diapers, adult incontinence products

• Latex paints and adhesives

8.2 Textile Industry

8.3 Cosmetics and Personal Care

8.4 Water Treatment and Swimming Pools

8.5 Electronics and Metal Finishing

8.6 Oil and Gas Industry

8.7 Paper and Pulp Industry

8.8 Detergents and Cleaning Products

8.9 Food Industry (E922 – Restricted/Limited Approval)

Regulatory Note on E922:

• European Union: NOT APPROVED (banned for food use)

• USA: Not listed as GRAS; limited use as flour improver with restrictions (21 CFR 172.802 – potassium bromate replacement)

• Japan: Permitted as flour treatment agent (restricted)

• Brazil: Permitted (restricted)

• Turkey: Not permitted as food additive (follows EU regulations)

8.10 Other Applications

9. Comparison with Other Persulfates

10. Toxicology and Safety

10.1 Acute Toxicity

10.2 Special Toxicity Concerns

10.3 GHS Classification

Signal word: DANGER

10.4 NFPA Rating

10.5 Target Organs

• Respiratory system (lungs, nasal passages)

• Skin

• Eyes

10.6 Known Occupational Diseases

• Persulfate-induced asthma (occupational asthma) – well-documented in hairdressers, chemical workers

• Allergic contact dermatitis – common in hairdressers handling hair bleaching products

11. Safety Precautions and Personal Protective Equipment (PPE)

Hazards:

• Strong oxidizer – may cause fire or explosion when in contact with combustible materials (organics, finely divided metals, reducing agents).

• Respiratory sensitizer – may cause occupational asthma.

• Skin sensitizer – may cause allergic contact dermatitis.

• Corrosive to eyes – causes serious eye damage.

• Harmful if swallowed or inhaled.

• Decomposes at elevated temperatures – releases oxygen, may increase fire intensity.

PPE (mandatory):

• Respiratory protection: P2 or P3 filter mask (for dust). Use half-mask or full-face respirator with P3 filter in case of poor ventilation or high dust concentration. For sensitized individuals, use supplied air respirator.

• Eye protection: Chemical splash goggles (EN 166) with indirect ventilation. Full face shield recommended.

• Gloves: Nitrile gloves (≥0.4 mm thickness). Butyl rubber or neoprene also suitable. Do not use natural rubber (latex) – may degrade.

• Protective clothing: Chemical-resistant apron or coverall (e.g., Tyvek, PVC, neoprene).

• Footwear: Closed-toe, chemical-resistant boots.

Engineering controls:

• Local exhaust ventilation (LEV) with dust collection.

• Dust containment (closed systems, dust collectors).

• Emergency eyewash stations and safety showers.

• Fire suppression system (dry chemical, CO₂, water spray).

• Keep away from combustible materials.

• No smoking, no open flames.

Storage conditions:

Incompatibilities (DO NOT MIX WITH):

• Organic compounds (solvents, oils, fats, paper, wood, cotton)

• Reducing agents (sulfides, sulfites, thiosulfates, hydrides)

• Finely divided metals (zinc, aluminum, magnesium, iron)

• Strong acids (generate oxygen)

• Strong bases (accelerate decomposition)

• Amines and ammonia (may form explosive compounds)

Firefighting:

• Hazard class: Oxidizer (UN 1492, Class 5.1)

• Extinguishing media: Water spray (large amounts) – the most effective; CO₂, dry chemical powder (for small fires). Do not use foam or dry chemical alone – oxidizer may decompose and generate oxygen.

• Firefighting instructions: Use water spray to cool containers. Evacuate area. Firefighters should wear SCBA and full protective gear.

• Runoff water: May contain persulfate; prevent entry into sewers and watercourses.

First aid:

• Inhalation: Move to fresh air. If breathing difficulty, administer oxygen. If symptoms (cough, wheezing, asthma) develop, seek immediate medical attention. Persons with persulfate sensitivity may require steroid inhalers.

• Skin contact: Remove contaminated clothing. Wash with copious water and soap for at least 15 minutes. If rash or irritation develops, seek medical attention.

• Eye contact: Rinse with water for at least 15 minutes, lifting eyelids. Remove contact lenses. Seek immediate medical attention.

• Ingestion: Rinse mouth. Do NOT induce vomiting. Drink water or milk (200–300 mL). Seek immediate medical attention. Never give anything by mouth to an unconscious person.

Spill cleanup:

• Small spills: Sweep up carefully (avoid dust generation) using non-sparking tools. Place in clean, dry, labeled container for disposal. Do not return to original container. Contaminated floors should be washed with water.

• Large spills: Evacuate area. Eliminate ignition sources. Wear appropriate PPE. Use non-sparking tools. Cover with damp sand or vermiculite. Collect in approved containers.

• Do not use combustible materials (sawdust, paper) for cleanup.

• Disposal: Dispose of as hazardous waste (oxidizer). Incineration is preferred (with strict temperature control). Do not dispose of with organic waste.

12. Environmental Fate

13. Storage and Shelf Life

13.1 Storage Conditions

13.2 Shelf Life and Degradation

13.3 Decomposition Warning Signs

• Pressure buildup in sealed containers (due to oxygen evolution) – DO NOT open if container is bulging; vent carefully in a fume hood.

• Caking (hard lumps) – indicates partial decomposition and/or moisture absorption.

• Yellow or brown discoloration – indicates decomposition.

• Pungent, acrid odor (ozone-like) – indicates decomposition.

14. Transport Information

Transport special precautions:

• Keep away from combustible materials during transport.

• Use clean, dry containers (no organic residues).

• Segregate from reducing agents, acids, bases, organic peroxides, and flammable materials.

• Load restraint to prevent shifting.

15. Synonyms and Common Names

• English: Potassium Persulfate, Potassium Peroxydisulfate, Dipotassium Peroxodisulfate, Dipotassium Peroxydisulfate, Potassium monopersulfate (CAUTION: not the same as potassium monopersulfate KHSO₅), Dipotassium Disulfate, Peroxydisulfuric Acid Dipotassium Salt, E922

• German: Kaliumpersulfat, Kaliumperoxodisulfat

• French: Persulfate de potassium, Peroxodisulfate de potassium

• Spanish: Persulfato de potasio, Peroxodisulfato de dipotasio

• Trade names: KPS, K-Persulfate, Oxone (potassium monopersulfate – different compound), potassium persulfate (generic)

Important Note: Potassium monopersulfate (KHSO₅, CAS 10058-23-8, Oxone®) is a different compound! Potassium persulfate (K₂S₂O₈) contains a peroxy bridge (–O–O–) between two sulfur atoms. Potassium monopersulfate (KHSO₅) contains only one sulfur with an –O–O–H group. Do not confuse them.

16. Potassium Persulfate vs. Potassium Monopersulfate (Important Clarification)

17. Frequently Asked Questions (FAQs)

Q1: Is potassium persulfate the same as potassium monopersulfate (Oxone)?
A1: No! They are different compounds. Potassium persulfate (K₂S₂O₈, CAS 7727-21-1) contains a peroxy bridge between two sulfur atoms. Potassium monopersulfate (KHSO₅, CAS 10058-23-8, sold as Oxone®) contains only one sulfur with an –O–O–H group. They have different properties and applications.

Q2: Is potassium persulfate safe to use?
A2: With proper PPE and handling procedures, yes. However, it is a strong oxidizer and respiratory/skin sensitizer. It can cause occupational asthma and allergic contact dermatitis, especially with repeated exposure (common in hairdressers). Always use dust control and PPE.

Q3: Why is potassium persulfate used in polymerization?
A3: It decomposes (thermally or with UV light) to form sulfate radical anions (SO₄·⁻) , which initiate free-radical polymerization of monomers such as styrene, butadiene, acrylates, vinyl chloride, and acrylamide. It is used in emulsion, suspension, and solution polymerization.

Q4: Is potassium persulfate allowed in food (E922)?
A4: No in the EU – banned. In the USA, it has restricted use as a flour improver (≤50 ppm). It is permitted in Japan and Brazil with restrictions. It is not a widely approved food additive.

Q5: How is potassium persulfate different from ammonium persulfate?
A5: Both are strong oxidizers and polymerization initiators. Key differences:

• Solubility: APS is much more soluble (58 g/100 mL vs. 4.7 g/100 mL for KPS)

• Residual cation: APS leaves NH₄⁺ (volatile as NH₃) vs. KPS leaves K⁺ (non-volatile)

• Stability: KPS is more thermally stable

• Cost: APS is lower cost

• Application: APS is more common; KPS is used when NH₄⁺ is undesirable

Q6: How should potassium persulfate be stored?
A6: Store in a cool (<30°C), dry (<50% RH), well-ventilated area. Keep away from organic materials, reducing agents, acids, bases, and combustible materials. Use HDPE, PP, or stainless steel containers. Do not store in carbon steel, aluminum, or copper containers. Tightly seal to prevent moisture absorption.

Q7: What happens when potassium persulfate decomposes?
A7: Decomposition (thermal, acid-catalyzed, or metal-catalyzed) produces oxygen gas, potassium sulfate, and sulfur trioxide. Oxygen evolution can cause pressure buildup in sealed containers. The reaction is exothermic and can accelerate if not controlled.

Q8: Can potassium persulfate cause a fire or explosion?
A8: Potassium persulfate itself is not flammable, but as a strong oxidizer, it can intensify fires and cause combustible materials (paper, wood, oil, organic solvents, finely divided metals) to ignite or explode. Keep away from combustibles!

Q9: How do I treat persulfate-induced asthma?
A9: Prevention is key (dust control, respiratory protection). Once sensitized, the only effective treatment is avoidance of persulfate exposure. Medical treatment includes bronchodilators, inhaled corticosteroids, and in severe cases, removal from exposure (change job). Persulfate-induced asthma is an occupational disease.

Q10: Is potassium persulfate used in hair bleach?
A10: Yes, it is used as an oxidizing agent and activator in hair bleaching products (usually as a component of powder bleach formulations). It is one of the causes of occupational asthma and allergic contact dermatitis in hairdressers.

18. Summary Table – Key Specifications at a Glance

*This TDS is prepared in compliance with ISO 11014-1 format and is intended for polymer chemists, textile engineers, cosmetic formulators, water treatment specialists, oil and gas professionals, and procurement personnel. Certificates of Analysis (CoA), Safety Data Sheets (SDS), and sample validation reports are available upon request.*