Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

Rodrigo Yepsen,Joaquín Roa,Leopoldo Gutiérrez,Pedro G Toledo

doi:10.3390/min11050539

Abstract

The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.

Highlights

Processing of low-grade ores rich in phyllosilicates is becoming more common in copper-molybdenum flotation plants [1]
The experimental results show that the copper and molybdenum concentrate grades decrease as the mica content increases which can be explained by the reduction in flotation of fully liberated particles of chalcopyrite and molybdenite
In the absence of micas, molybdenite flotation is strongly reduced in seawater at pH 11, which agrees with previous studies [18]

Summary

Introduction

Processing of low-grade ores rich in phyllosilicates is becoming more common in copper-molybdenum flotation plants [1] These gangue species get dispersed in suspension as ultra-fine particles, modifying the rheological behavior of mineral suspensions and negatively affecting the efficiency of the process through several mechanisms [2,3]. An interesting case study is flotation in seawater because it was reported that the depressing effect of clay minerals becomes stronger in this aqueous medium [7]. Micas such as muscovite and biotite are phyllosilicates usually found in complex copper ores. The monoclinic crystal structure of muscovite consists of tetrahedral sheets bonded together by interchanging layers of K+

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