Synthesis of High-Purity Hydroxyapatite and Phosphoric Acid Derived from Moroccan Natural Phosphate Rocks by...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Natural phosphate rocks contain valuable minerals like hydroxyapatite (HAp) but are often contaminated with metallic cations.
• These impurities limit the application of HAp in various sectors.
• Purification of HAp and its subsequent conversion into valuable products like phosphoric acid are crucial.

Purpose of the Study:

• To synthesize and purify hydroxyapatite (HAp) from natural Moroccan phosphate using a dissolution-precipitation (DP) technique.
• To investigate the efficiency of the DP method in removing metallic impurities from HAp.
• To produce high-quality phosphoric acid (PA) and gypsum (GP) from the purified HAp.

Main Methods:

• Synthesis and purification of HAp from Moroccan phosphate rock.
• Application of the dissolution-precipitation (DP) technique for impurity removal.
• Digestion of purified HAp with sulfuric acid to produce phosphoric acid and gypsum.

Main Results:

• The DP technique significantly reduced metallic cation contamination in HAp, with removal efficiencies up to 90% for Cd and Pb after one cycle and total removal after three cycles.
• Purified HAp yielded phosphoric acid with over 94% removal efficiency for most cations and high-quality gypsum.
• The process demonstrated effectiveness in reducing a broad spectrum of cationic impurities.

Conclusions:

• A simple and flexible dissolution-precipitation process is effective for purifying hydroxyapatite from natural phosphate sources.
• This method enables the production of valuable materials such as purified HAp, high-purity phosphoric acid, and gypsum.
• The study highlights a practical approach for valorizing phosphate rock while minimizing cationic impurities.