Flotation Separation of Diaspore and Kaolinite by Using a Mixed Collector of Sodium Oleate-Tert Dodecyl Mercaptan.

Xiaofei Man,Xiqi Ma,Leming Ou,Saizhen Jin,Chenliang Wang

doi:10.3389/fchem.2019.00813

Abstract

Sodium oleate (NaOl), a collector in diaspore flotation, has been widely used for more than 30 years, while its low selectivity becomes an issue under today's process requirement. This study introduced tert dodecyl mercaptan (TDM) together with NaOl as a mixed collector to improve selectivity in diaspore flotation. We found that using the mixed collector of NaOl/TDM (total concentration 0.1 mM, the molar ratio 8:2 of NaOl: TDM) at pH = 9–10 significantly effectively separated diaspore and kaolinite. Comparing the recovery of Al2O3 and the ratio of Al2O3 to SiO2 (A/S) treated by NaOl/TDM (pH = 9) and NaOl (pH = 10), the Al2O3 recovery and A/S in concentrate for NaOl/TDM are 7.5% and 2.2 higher than that for NaOl in mixed mineral flotation. Also, surface tension measurements, Zeta potential measurements and Fourier Transform Infrared (FTIR) spectra analysis were used to examine its selectivity from a flotation mechanical perspective. Surface tension measurements show that mixed collector NaOl/TDM has stronger surface activity and hydrophobic association than NaOl. The results of Zeta potential measurements and FTIR spectra analysis indicate that NaOl and TDM can selectively co-adsorb diaspore through physical adsorption. Moreover, the adsorption of TDM promotes the adsorption of NaOl on diaspore. However, when NaOl/TDM treats on kaolinite together, TDM can hardly adsorb on mineral surface, nor can it promote the adsorption of NaOl.

Highlights

Bauxite is an important raw material for industrial production of alumina (Zhang et al, 2017a, 2018a)
The recovery of NaOl to diaspore reaches the maximum of 84.6%, but at this time the recovery of NaOl to kaolinite reaches 16.7%, so single collector NaOl cannot make an efficient separation between diaspore and kaolinite
We considered further investigating the flotation of diaspore and kaolinite with NaOl/tert dodecyl mercaptan (TDM) mixed collector in order to obtain better separation effect

Summary

Introduction

Bauxite is an important raw material for industrial production of alumina (Zhang et al, 2017a, 2018a). In China, diaspore is the primary mineral in bauxite, accounting for more than 98% of the total reserves (Zhang et al, 2016). China’s bauxite resources have the characteristics of high alumina, high silicon, and low mass ratio of Al2O3 to SiO2 (A/S) (Liu et al, 2007; Hong et al, 2008; Jiang et al, 2012). Bauxite with A/S ratio of 4–6 accounts for about 60% of the total (Liu et al, 2007; Jiang et al, 2010a). It is necessary to pre-desilicate bauxite to improve its mass ratio of A/S

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Results

Conclusion