Study on flotation performances and adsorption mechanism of 2-carboxyethylphenylphosphinic acid to cassiterite

A novel collector, 2-carboxyethylphenylphosphinic acid (CEPPA), was first used in the flotation of cassiterite. The flotation performances and the adsorption mechanism of CEPPA on cassiterite were investigated by flotation tests, adsorption experiments, zeta potential measurements, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The results indicated that CEPPA had strong collecting power for cassiterite and fluorite over a wide pH range but little on quartz. In the separation of the cassiterite–quartz mixture, a concentrate containing 90.9% SnO2 was obtained with a recovery of 95.7% at pH 7.0. The cassiterite in the cassiterite–fluorite mixture could be effectively separated using 300 mg/L sodium silicate in conjunction with 60 mg/L CEPPA, and a concentrate with a grade of 90.3% SnO2 and a recovery of 92.6% was achieved at neutral pH. Zeta potential analysis demonstrated that the adsorption process involved both physical and specific forces. The results of FTIR and XPS further suggested that the four O atoms of CEPPA reacted with the Sn atoms on cassiterite surface, forming a complex which was similar to the Sn–CEPPA precipitate, and hydrogen bonding adsorption could have taken place between the terminal hydroxyl groups and CEPPA anions.