Utilization of Lead Nitrate to Enhance the Impact of Hydroxamic Acids on the Hydrophobic Aggregation and Flotation Behavior of Cassiterite.

Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate (OHA) were used as the collectors through micro-flotation, focused beam reflectance measurement (FBRM) and a particle video microscope (PVM), zeta potential, and the extended DLVO theory. Micro-flotation tests confirmed that LN activated the flotation of cassiterite using the hydroxamic acids as collectors. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to capture in situ data on the changes in size distribution and morphology of cassiterite aggregates during stirring. The FBRM and PVM image results indicated that the addition of LN could promote the formation of hydrophobic aggregates of fine cassiterite, when BHA or HHA was used as the collector, and reduce the dosage of OHA needed to induce the formation of hydrophobic aggregates of cassiterite. The extended DLVO theory interaction energies indicated that the presence of LN could decrease the electrostatic interaction energies (Vedl) and increase the hydrophobic interaction energies (Vhy) between cassiterite particles, resulting in the disappearance of the high energy barriers that existed between the particles in the absence of LN. Thus, cassiterite particles could aggregate in the presence of LN when BHA, HHA, or a low concentration of OHA was used as the collector.

Effect of Pre-Sulfidization on the Octadecyl Amine Adsorption on the Smithsonite Surface and Its Flotation.

The low-grade zinc oxide ore was sulfidized to increase the efficiency of flotation, but the effect of pre-sulfidization on the adsorption mechanism of octadecyl amine (ODA) on the smithsonite surface is currently unclear. In this study, the effect of pre-sulfidization on the adsorption mechanism of ODA and the flotation behavior was studied using smithsonite and pre-sulfidized smithsonite as the samples by zeta potential, contact angle measurement, total organic carbon analyzer (TOC), quartz microcrystalline balance (QCM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and micro-flotation tests. Micro-flotation tests showed that the pretreatment of sulfidization could improve the floatability of smithsonite. Zeta potential and contact angle measurements demonstrated that pre-sulfidization could favor the adsorption of ODA, which is further confirmed by the adsorption tests of ODA using TOC and QCM. Furthermore, FTIR and XPS analysis showed that pre-sulfidization changes the adsorption mode of ODA, changing it from physical adsorption to chemical adsorption. These results suggested that the favorable effect of pre-sulfidization on the adsorption of ODA and the flotation of smithsonite might provide important guidance for industrial application.

Utilization of Phytic Acid as a Selective Depressant for Quartz Activated by Zinc Ions in Smithsonite Flotation.

It is difficult to separate smithsonite from quartz with metal ion activation through flotation using sodium oleate (NaOL) as the collector. The inevitable Zn2+ in the flotation process of zinc oxide ore makes the separation of smithsonite and quartz more difficult. Thus, this study investigated the use of phytic acid (PA) as a flotation depressant to separate smithsonite from Zn2+-activated quartz while utilizing sodium oleate as the collector. Microflotation tests indicated that phytic acid could selectively inhibit the flotation of Zn2+-activated quartz without affecting the flotation of smithsonite. The measured zeta potentials revealed that the existence of phytic acid hindered sodium oleate adsorption to the surface of Zn2+-activated quartz but had little influence on the adsorption of smithsonite. Zn2+ dissolution tests and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis indicated that the phytic acid could dissolve the Zn2+ from the minerals' surfaces into the solution. In conjunction with X-ray photoelectron spectroscopy results, the analysis indicated that phytic acid could adsorb onto the Zn2+-activated quartz surface and eliminate active sites for sodium oleate adsorption by dissolving the active Zn2+ from the quartz surface into the solution.

Hydrophobic Flocculation of Fine Cassiterite Using Alkyl Hydroxamic Acids with Different Carbon Chain Lengths as Collectors.

This work investigated the hydrophobic flocculation of cassiterite using four alkyl hydroxamic acids with varying carbon chain lengths, i.e., hexyl hydroxamate (C6), octyl hydroxamate (C8), decyl hydroxamate (C10) and dodecyl hydroxamate (C12), as collectors. Microflotation tests were performed to investigate the flotation behaviour of cassiterite in the presence of the four alkyl hydroxamic acids. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to analyse and monitor the real-time evolution of the particle size distribution of cassiterite and the images of flocs during flocculation. The extended DLVO theory interaction energies between the cassiterite particles were calculated on the basis of the measured contact angle and the zeta potential of cassiterite to determine the aggregation and dispersion behaviour of the cassiterite particles. The microflotation test results suggested that the floatability of cassiterite improved with the increase in the carbon chain length of hydroxamates. FBRM, PVM images and extended DLVO theory calculation results indicated that when C6 was used as the collector, the cassiterite particles could not form hydrophobic flocs because the total potential energy between them was repulsive. When C8, C10 and C12 were used as collectors, the energy barrier amongst particles decreased with increasing hydroxamate concentration. The lowest concentrations of C8, C10 and C12 that could cause the hydrophobic aggregation of cassiterite were approximately 1 × 10-3, 1 × 10-4 and 2 × 10-5 mol/L, respectively. The aggregation growth rate and apparent floc size increased with an increasing collector concentration. Hydroxamic acid with a longer carbon chain could induce the cassiterite particles to form larger flocs at a lower concentration in a shorter time.

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

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.