Selective adsorption mechanism of dodecylamine on the hydrated surface of hematite and quartz

Abstract

• The hydration structure of quartz and hematite were considered in the calculations. • DDA and CCS are physically adsorbed on the hydrated surface of quartz and hematite. • The selectivity of dodecylamine to quartz is better than that of hematite. • The selectivity of starch to hematite is better than that of quartz. Flotation is one of the most effective methods to selectively separate refractory hematite from quartz. However, the separation mechanism of the hydrophilic minerals of hematite and quartz is still poor understood. In this work, the selective adsorption behaviors of the representative collector dodecylamine (DDA) and depressant causticized cassava starch (CCS) on the hydrated surface of quartz and hematite were systematically investigated based on experimental and computational methods. Accordingly, microflotation results showed that the TFE grade could be significantly improved by increasing the dosage of DDA appropriately, but it had a negative effect on the concentrate recovery, however, with the increase of CCS dosage, concentrate recovery could be improved, but TFE grade could be reduced to a certain extent. Solution-chemistry analysis indicated that the positively charged RNH 3 + was the main component of DDA at pH 7. Because the Zeta potential of quartz is more negative than that of hematite, DDA can be selectively adsorbed on the quartz surface by electrostatic attraction. The DFT calculations showed that the adsorption (inhibition) of starch fragments on the hydrated surface of hematite was stronger than that of quartz, while the collector RNH 3 + had a better selective adsorption interaction with the starch-modified hydrated surface of quartz, resulting in the selective separation of quartz from hematite. This work shed new light on the selective adsorption mechanism of flotation reagents on the hydrated surface of oxide minerals.