Study on the Effect of Fe3+ on Zircon Flotation Separation from Cassiterite Using Sodium Oleate as Collector

The effect of ferric ions (Fe3+) on the flotation of zircon and cassiterite using sodium oleate (NaOL) was investigated by single mineral flotation tests, adsorption density tests, zeta potential measurements, solution chemistry analyses, and FTIR analyses. It is difficult for zircon to be separated from cassiterite by using NaOL alone. Nevertheless, the flotation of zircon was activated while that of cassiterite was depressed in the presence of Fe3+. Adsorption density tests indicated that the addition of Fe3+ enhanced the adsorption of NaOL on zircon surfaces, whereas it receded on cassiterite surfaces. Zeta potential measurements and solution chemistry analyses found that H(OL) 2 − was the predominant species to determine the flotation behaviors of zircon and cassiterite. Furthermore, the addition of Fe3+ at pH < 8 reduced the negative charges on the zircon and cassiterite surfaces. It was confirmed that the positive charges of zircon were caused by the positively charged species of Fe3+, including Fe3+, Fe(OH)2+, and Fe(OH) 2 + . Meanwhile, these results revealed that the hydroxy complex and the precipitate of Fe(OH)3(s) adsorbed onto the cassiterite surfaces caused the flotation of cassiterite to be inhibited. It can be concluded from FTIR analyses that the peaks of zircon at 894.14 cm−1 and 611.65 cm−1 were strengthened and the adsorption on zircon surfaces was found to be chemisorption due to the addition of Fe3+, whereas both chemical and physical adsorptions of NaOL on cassiterite surfaces were weakened, resulting in the different flotation behaviors of zircon and cassiterite in the presence of Fe3+.