ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Role of calcium ions and their interaction with depressants in phosphate flotation

S. E. El-Mofty and A. A. El-Midany

Cairo University, Cairo, Egypt

E-mail: mpm_cu@yahoo.com

Abstract: The commonly utilized flotation scheme in phosphate industry is reverse flotation using fatty acids in acidic media adjusted by H₂SO₄. The acidity of the flotation pulp results in presence of different ionic species that play a crucial role in modifying the minerals’ surfaces. Therefore, the flotation of pure phosphate was investigated in presence of H₂SO₄ for pH adjustment and potassium oleate, potassium dihydrogen phosphate, potassium oxalate, calcium nitrate and potassium sulfate. The reason behind using these chemical reagents is to study the effect of different ionic species on the phosphate flotation. Flotation results as well as thermodynamic analysis indicated that the formation of aqueous calcium/phosphate complexes (i.e., CaHPO_4(aq)) on hydroxyapatite surface is the most significant species in depressing phosphates. The Ca⁺⁺ concentration, particularly in acidic pH, showed a great effect on the formation of aqueous CaHPO₄. The aqueous CaHPO₄ concentration sharply decreased by increasing Ca⁺⁺ concentration where the depression becomes more challenging. Therefore, the main purpose of adding depressants is to reduce Ca⁺⁺ ions by forming Ca-depressant complexes.

Keywords: Phosphate ; Depressants ; Calcium ions ; Oxalate ; Sulfate ; Reverse flotation ; Acidic media 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0499-2

Chemical Papers 72 (10) 2641–2646 (2018)