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✅ Phosphoric Acid Production Methods

Phosphoric acid (H₃PO₄) is primarily produced through two main industrial processes: the Wet Process and the Thermal Process.

The Wet Process is the most widely used method globally, mainly for producing phosphoric acid for fertilizers.

Reaction:
The phosphate rock reacts with sulfuric acid and water to form phosphoric acid and gypsum (calcium sulfate dihydrate) as a by-product.
Chemical Reaction:
$Ca₅(PO₄)₃F + 5H₂SO₄ + 10H₂O → 3H₃PO₄ + 5CaSO₄·2H₂O + HF$
$C a_{5} (P O_{4})_{3} F + 5 H_{2} S O_{4} + 10 H_{2} O \to 3 H_{3} P O_{4} + 5 C a S O_{4} \cdot 2 H_{2} O + H F$
Filtration:
Gypsum is separated from the liquid phosphoric acid.
Concentration:
The phosphoric acid solution is concentrated by evaporation to the desired strength.

The Thermal Process produces very high-purity phosphoric acid, suitable for food, pharmaceutical, and electronic industries.

Combustion:
Elemental phosphorus is burned in air to form phosphorus pentoxide (P₂O₅).
Chemical Reaction:
$P₄ + 5O₂ → 2P₂O₅$

$P_{4} + 5 O_{2} \to 2 P_{2} O_{5}$

Hydration:
The phosphorus pentoxide reacts with water to form phosphoric acid.
Chemical Reaction:
$P₂O₅ + 3H₂O → 2H₃PO₄$

$P_{2} O_{5} + 3 H_{2} O \to 2 H_{3} P O_{4}$

Produces high-purity phosphoric acid (food-grade, electronic-grade, pharmaceutical-grade).
Higher production costs due to the use of elemental phosphorus and energy.
Preferred when stringent quality is required.

Aspect	Wet Process	Thermal Process
Purity	Medium (industrial use)	High (food, pharma, electronic use)
Cost	Lower	Higher
Main Use	Fertilizers, industrial applications	High-purity applications
By-products	Gypsum	Minimal