Overview of 85% Phosphoric Acid

85% phosphoric acid a 85 wt% aqueous solution of H₃PO₄ is a high-purity, non-volatile, syrupy liquid used across industries. It’s colorless and odorless in its commercial form. This concentration is favored for its ideal balance of acidity and physical properties; higher concentrations crystallize, while lower concentrations lack sufficient reactivity .

Production methods include the wet process (treating phosphate rock with sulfuric acid) and dry/thermal process (burning elemental phosphorus to make food-grade acid). For reuse applications, ensuring a minimum 85% purity is crucial to maintain performance in fertilizers, cleaning agents, and food uses.
 

Reuse in Fertilizer Production

  1. Liquid Fertilizer Formulation
    Phosphoric acid is the backbone of phosphate fertilizers: Monoammonium phosphate (MAP) and Diammonium phosphate (DAP) derive directly from H₃PO₄. Liquid application such as fertigation uses 85% acid diluted to supply soluble phosphorus, vital for plant metabolic functions like ATP production, root development, and flowering.
    Reusing acid from industrial processes (like etching baths or phosphating water) mitigates costs and reduces phosphate rock demand. Such circular reuse aligns with sustainable tropical agriculture goals in Singapore and Southeast Asia.

  2. pH Adjustment & Irrigation Cleanliness
    Low-cost reclaimed acid can adjust irrigation system pH, ensuring phosphate availability without scale buildup in pipes Alliance Chemical. It also dissolves lime deposits, maintaining efficient drip and sprinkler operations. Recycled 85% acid, analyzed for purity, is ideal for greenhouse and hydroponic systems.
     

Applications in Cleaning Agents and Surface Treatment

  1. Rust & Mineral Deposits Removal
    With strong acidity, 85% H₃PO₄ reacts with iron oxide (rust), converting it to ferric phosphate, which is easily removed Bell Chem. Similarly, it dissolves limescale and soda deposits in pipes, boilers, and kitchen surfaces. Reclaimed acid from phosphating units shows renewed potential in industrial cleaning operations.

  2. Detergent & Sanitizing Chemicals
    Phosphoric acid serves as a pH adjuster, chelating agent, and buffer in both household and institutional cleaners. For example, recycled 85% acid can be reused in controlled formulations e.g., floor cleansers, degreasers, and dishwashing compounds. The reuse cuts fresh acid consumption and lowers chemical disposal.

  3. Water Treatment & Scale Control
    In water treatment systems (e.g., cooling towers), phosphoric acid prevents scale formation. Reusing acid from cleaning and fertilizer plants helps maintain water quality and equipment lifespan.
     

Food Industry and Food Chemical Uses

  1. Acidulant in Beverages & Food Processing
    Food-grade 85% phosphoric acid, meeting strict purity criteria, is used to impart tanginess in carbonated drinks (e.g., colas), processed cheeses, jams, and acid-stable baked goods . Aged 85% acid, when re-purified and certified, can be reintroduced into food chains, reducing waste while maintaining quality.

  2. pH Control & Preservation
    Processed meats, cheeses, oils, and jellies rely on 85% acid to stabilize pH and prevent microbial spoilage . The acid can also improve edible oil clarity and flour quality. When food-grade acid is reclaimed via distillation or filtration it can be reused in these processes.

  3. Surface Sanitizing in Food Production
    In dairy and brewing environments, phosphoric acid sanitizes equipment and surfaces without leaving harmful residues. Recycling in rinse cycles, subject to microbial testing, reduces fresh acid usage and processing costs.
     

Sustainability & Environmental Considerations

  1. Resource Efficiency & Circularity
    Phosphate rock is a limited resource, and reclaiming 85% phosphoric acid conserves it . Recovering acid from wastewater, treated sewage sludge ash aligns with emerging recycling technologies .

  2. Environmental Impact of Manufacturing
    Traditional acid production, particularly the wet process, generates phosphogypsum waste and consumes energy . Reuse lessens environmental load, less mining, lower sludge release, and reduced CO₂ emissions.
     

Safety, Handling, and Quality Control

85% H₃PO₄ is corrosive; handling requires chemical-resistant PPE, spill containment, and proper ventilation. Reuse requires analytical testing for purity, checking contaminants like heavy metals or organics. Food-grade reuse demands re-certification (COA, microbial assays). UN regulations designate concentrated phosphoric acid under UN 1805 regulating transport and labeling.
 

Regulatory Context in Singapore

Under the Singapore Food Agency (SFA), phosphoric acid is recognized as E338, permitted in beverages, processed foods, and cheese with maximum residual limits. Suppliers must provide MSDS, COA, and Halal or Kosher certification when applicable. Industrial and fertilizer uses also require documentation to ensure safety and environmental compliance.
 

Conclusion

Reusing 85% phosphoric acid is an intelligent, sustainable strategy that offers economic benefit, resource conservation, and operational efficiency. Whether used for fertilizers, industrial cleaning, or food-grade formulations, reclaimed acid if properly purified can fulfill key roles across sectors in Singapore's industrial ecosystem.

By embracing circular chemical practices, industries can reduce phosphate mining dependency, minimize environmental pollution, and enhance cost-effectiveness. As regulatory frameworks evolve to support chemical reuse, repurposing 85% phosphoric acid is not just innovative it’s essential for resilient and sustainable industrial growth. For inquiries about reclaimed or food-grade 85% phosphoric acid for fertilizer, cleaning, or food applications in Singapore, please contact our team here.
 

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