Interaction mechanism of magnesium ions with cassiterite and quartz surfaces and its response to flotation separation

The Influence of Kaolinite and Quartz on Stability of Coal Froths - A Rheology and Structure Study

Kaolinite and quartz are the common gangue minerals found in raw coal; however, their effects on stability of coal froths and subsequent settling of coal flotation products have not been investigated. In this study, in the coal froths batch settling tests, the amount of froth floating on top of water was 275, 325, 355, and 405 mL for coal concentrates generated with 0, 20, 40, and 60 wt % kaolin Q38, respectively, while that was almost the same (300-306 mL) for coal froth concentrates generated with 0, 20, 40, and 60 wt % quartz added in flotation, respectively, which turned out that the kaolinite could increase the stability of coal froth, while quartz could not. To investigate the mechanism, oscillatory rheology and scanning electron microscopy (SEM) were applied. The results of the oscillatory rheology suggested that the structural strength in coal froth was strengthened with the addition of kaolinite. In addition, images of Plateau borders by SEM illustrated that the addition of kaolinite in flotation increased the size of Plateau borders and generated network structures in the Plateau borders. However, as a comparison, the addition of quartz did not cause an obvious change for the oscillatory rheology and SEM results of coal froth. Based on the results, it can be concluded that network structures were generated in the Plateau border of coal froth with the addition of kaolinite, which increased its structural strength and retarded the drainage in froth. As a result, the stability of the coal froth increased.

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.

Influences of Ferric Ions and Fe as a Minor Element in the Lattice on the Floatability of Cassiterite

In this study, synthetic pure cassiterite and cassiterite doped with two different Fe contents were successfully recrystallized by means of sintering. Their crystal structure and chemical compositions were characterized by X-ray powder diffraction (XRD) as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) analysis. Their floatability was studied by microflotation with a diphosphonic acid surfactant named Lauraphos301 as a collector. Unlike the addition of ferric ions in solution, which strongly depressed the floatability of all of the cassiterite samples, a much higher flotation efficiency of the Fe-doped cassiterite samples was found especially at lower collector concentrations. The cassiterite floatability is proportional to the Fe content in cassiterite at a broad range of pH, and the recovery has the following order: cassiterite with 1417 ppm Fe > cassiterite with 1165 ppm Fe > pure cassiterite. The electrokinetic behavior of the cassiterite samples with and without the collector was studied by electrophoretic measurements and revealed that the chemical interaction dominated the adsorption. With the help of the particle shape analysis, a more angular shape was found for the Fe-doped cassiterite samples. Moreover, without the influence of particle shape, much abundant adsorption of Lauraphos301 was found on the Fe-doped cassiterite samples by AFM topography imaging. The minor amount of Fe in the cassiterite lattice and a more angular shape of the Fe-doped cassiterite samples were believed to enhance floatability collectively. The study reveals that the influence of the chemical composition of the minerals on flotation was almost inextricably bound up with particle morphology and emphasizes the importance of considering both factors and investigating them individually for the flotation study.

Effects of Interfacial Hydroxylation Microstructure on Quartz Flotation by Sodium Oleate

Quartz, a common inorganic nonmetallic mineral, is usually removed or purified by beneficiation, normally flotation. Given the strong polarity of the quartz surface, it is easy to hydrate to form a hydroxylation layer, which makes it impossible to float quartz with sodium oleate (OL) used alone. An ideal flotation method for quartz is preactivation with Ca²⁺, followed by collection with OL. Herein, the effects of surface hydroxylation on the adsorption of the anionic collector OL on the quartz surface before and after Ca²⁺ activation are systematically investigated by density functional theory (DFT) calculations. The results show that the displacement adsorption of surface hydroxyl substituted by OL^- is not feasible in thermodynamics, and the OL^- can only bind to the H atoms of the hydroxylated quartz surface via hydrogen bonds, namely, hydrogen binding adsorption. Due to the electrostatic repulsion and steric hindrance effect induced by the surface hydroxylation structure, the adsorption ability of OL^- on the quartz surface mediated by hydroxyl bridges is very weak, which is insufficient to realize quartz floating. However, Ca²⁺ ions are easily adsorbed on the hydroxylated quartz surface, providing favorable active sites for subsequent adsorption of OL^-, thus becoming a credible solution for the industrial flotation of the strong hydrophilic mineral quartz. These findings shed some new insights for accurately understanding the flotation mechanism of strongly hydrophilic oxide minerals and are beneficial to promoting the development of mineral flotation fundamentals.

The Flotation Separation of Magnesite and Limonite Using an Amine Collector

In order to reduce the iron impurities in magnesite ore and improve the purity of magnesium products, the difference in floatability between magnesite and limonite has been studied by using mixtures with a collecting agent—KD (cationic amine collectors, containing soluble components). Sodium hexametaphosphate, pH, sodium silicate, and sodium carboxymethyl cellulose were used as regulators. Adsorption mechanisms of the reagents on minerals were analyzed by a zeta potential analyzer and infrared spectroscopy. Sodium silicate increased the floatability of both minerals at 11.6. All the three regulators reduced the zeta potential of both minerals, while KD increased the zeta potential of magnesite and decreased the zeta potential of limonite. All the three regulators were likely chemically adsorbed on the surface of both minerals; KD has electrostatic adsorption on the surface of the minerals.

A New Collector for Effectively Increasing Recovery in Copper Oxide Ore-Staged Flotation

A new method, staged flotation for effectively increasing the recovery of ultra-fine copper oxide ore with a new type of collector (ZH-1, C3-5 carbon chain xanthate) is proposed for the first time. The flotation process and mechanism were examined by flotation tests, entrainment rate analysis, laser particle size experiments and microscopic imagery as well as economic feasibility analysis. It was demonstrated that the collector isoamyl sodium xanthate (ISX) shows a good collection ability (recovery exceeded 95%) for azurite, but the recovery was relatively much lower for malachite (only near 80%) due to the different particle size distribution. The new type of xanthate ZH-1 has shown a high-efficiency collection performance for fine-grained malachite. The recovery achieved for −10 μm malachite was more than 95% when the ZH-1 dosage was 150 mg/L, while the average particle size of −10 μm malachite sharply increased from 4.641 μm to 9.631 μm. The batch flotation results indicated that the copper oxide flotation recovery increased from 79.67% to 83.38%, and the grade also raised from 18.08% to 18.14% after using the staged flotation technology with ZH-1 as collector during the flotation of −25 μm ore. It was confirmed that this technology was quite effective for the recovery of copper oxide at the Dishui Copper Processing Plant, which successfully increased its gross profit by 1.6 million US$ per year.

Life cycle analysis of copper-gold-lead-silver-zinc beneficiation process

Gold, silver, lead, zinc, and copper are valuable non-ferrous metals that paved the way for modern civilisation. However, the environmental impacts from their beneficiation stage was always overlooked. This paper analysed the life cycle environmental impacts from the beneficiation process of gold-silver-lead-zinc-copper combined production. The analysis is conducted by utilising the SimaPro software version 8.5. The life cycle assessment methodologies followed are the International Reference Life Cycle Data System (ILCD) method, the IMPACT 2002+ method, and the Cumulative Energy Demand Method (CED). The most significant impact categories are ecotoxicity, climate change, human toxicity, eutrophication, acidification, and ozone depletion among nearly 15 impact categories which are assessed in this study. The analysis results from the ILCD method indicate that there is a noteworthy impact on ionising radiation caused by the beneficiation process. Out of the five metals considered, gold and silver beneficiation impacts the most while lead‑zinc beneficiation impacts the least. Gold beneficiation has most impacts on the category of climate change and ecosystems. Other major impact categories are ionising radiation, terrestrial eutrophication, photochemical ozone formation, human toxicity, and acidification. The IMPACT 2002+ method shows the overall impact is on ecosystem quality and human health from this combined beneficiation process, dominantly from gold‑silver beneficiation. The life-cycle inventory results show that the blasting process and the amount of electricity consumption in the beneficiation process contribute to cause significant amount of environmental impacts. The comparative impact results are presented and discussed in detail in this paper. Sensitivity analyses are presented based on various electricity grid-mix scenarios and energy-mix scenarios, and the results suggest that electricity grid mix has a dominant effect over the fossil-fuel mix. This paper also highlights the potential steps which could cut down the environmental effects by integrating renewable-energy technologies.