OPTIMIZATION OF ACID DECOMPOSITION OF WASHED CALCINED PHOSPHOCONCENTRATE USING A MIXED SECONDARY SULFURIC–EXTRACTION PHOSPHORIC ACID SYSTEM: CHEMICAL AND FTIR INVESTIGATION
DOI:
https://doi.org/10.61151/stjniet.v11i1.999Keywords:
Acid decomposition, Washed calcined phosphoconcentrate, Secondary sulfuric acid, Extraction phosphoric acid, Available phosphorus, Ammonium phosphate, FTIR, Process optimizationAbstract
This work examines the acid decomposition of washed calcined phosphoconcentrate using a mixed secondary sulfuric and extraction phosphoric acid feed (H₂SO₄:H₃PO₄ = 1:0.75) across a dosage range of 50–110 units. Products were characterized by total, citrate-soluble and water-soluble P₂O₅, free P₂O₅, total CaO and nitrogen content; structural changes were analyzed by FTIR spectroscopy. Increasing acid dosage enhanced conversion of mineral phosphorus into plant-available fractions and promoted ammonium incorporation after neutralisation, while reducing CaO content. FTIR results confirmed orthophosphate formation and ammonium-phosphate bonding, supporting the production of liquid complex fertilizer precursors. Optimal balance between available phosphorus and controlled free acidity was achieved at 85–95 units. The study provides process-relevant recommendations for up-scaling using secondary acid streams.
