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• The interfacial water in the NaOL system is more strongly hydrogen bonded than for the DDA and mixed collector systems. • The alignment of interfacial water molecules in the DDA system was more disrupted. • The COO– group stretches deeper into water than NH 4 + groups. • It is hard for DDA to form a stable compact and DDA has a tendency to form a bilayer. The molecular structure and orientation of collectors and water molecules on bubble surfaces in ore pulp is a fundamental phenomenon in the process of froth flotation. Considering the adsorption behavior and orientation of collectors and water molecules at the air/solution interface is of particular significance. In this study, the molecular structure and orientation of an aqueous solution of mixed dodecylamine hydrochloride (DDA) and sodium oleate (NaOL) with different molar ratios, and water molecules were examined at the air/solution interface and characterized using a combination of surface pressure measurements, sum frequency vibrational spectroscopy (SFVS) and molecular dynamics (MD) simulations. Both individual NaOL and DDA collectors were observed to be well ordered at the interface, while gauche defects appeared in some mixed collector systems. The ordering of interfacial water molecules in the presence of collectors with increasing molar ratios of NaOL to DDA is manifested by an enhancement of OH symmetric stretch from tetrahedrally coordinated water and a decreased bond disorder in the molecular arrangement or a "liquid-like" structure. In these mixed collector systems, the COO– group from NaOL stretches deeper into water than NH 3 + groups from DDA, and Na cations originating from NaOL distribute closer to COO– groups compared with the Cl originating from DDA to NH 3 + groups. The interfacial water in the single NaOL system is more strongly hydrogen bonded than those in the DDA and mixed collector systems. Conversely, the alignment of interfacial water molecules in the DDA system was more disrupted. These results provide a better understanding of the ordering of mixed NaOL/DDA collectors, as well as the orientation of water molecules at the air/water interface. This might therefore provide valuable insight into the relationship between the flotation phenomena and molecular characteristics of collectors at the air/water interface and should help to improve the froth flotation technology. [ABSTRACT FROM AUTHOR]

In this study, the effect of sodium pyrophosphate (NaPP) on the separation of apatite from dolomite by flotation was systematically investigated. Flotation results revealed that NaPP could selectively depress the flotation of apatite, thus realizing the separation of apatite from dolomite. Further, the selective depression mechanism of NaPP was studied through zeta potential measurements, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results demonstrated that the adsorption of sodium oleate (NaOL) onto apatite surface was depressed by the preferential interaction of NaPP with active Ca sites. For dolomite, while the presence of NaPP hindered the interaction of NaOL with active Ca sites, it appeared to enhance the reactivity with active Mg sites. Thus, the adsorption of NaOL onto dolomite surface was hardly influenced. In this way, the separation of apatite from dolomite was achieved. [ABSTRACT FROM AUTHOR]

Dealing with waste acid generated in phosphoric acid (H 3 PO 4) production has always been a problem due to the lack of cost-effective and environment-friendly disposal technology. This study introduces a novel method of utilizing the waste acid as a depressant in collophane flotation aiming at reusing waste acid and reducing the consumption of sulfuric acid (H 2 SO 4) in flotation plants. Its effectiveness was confirmed by flotation test in lab- and industrial-scale test. The depression mechanism is investigated via solution chemistry calculation and scanning electron microscope analysis. Laboratory-scale flotation results indicate that the utilization of waste acid coupled with H 2 SO 4 can strengthen depression performance on collophane, improving recovery efficiency compared with the use of H 2 SO 4 alone as depressant. Results demonstrate that H 2 PO 4 − is the effective species in waste acid. It depresses the flotation of collophane by reacting with active Ca sites on the surface to form CaHPO 4 and Ca(H 2 PO 4) 2 , thus preventing collector adsorption and reducing collophane surface hydrophobicity. The application of waste acid in industrial test shows the flotation recovery increases by 1% accompanied with the reduced consumption of H 2 SO 4 by 30.03% (from 15.5 kg/t to 10.8 kg/t). An increased profit of 890,043 RMB in a month is achieved due to the application of waste acid. Notably, approximately 197,000 t waste acid is consumed for a month, which brings considerable environmental benefits. In summary, the application of waste acid in collophane flotation is an efficient, economical, and eco-friendly alternative for the treatment of waste acid. • Waste acid could be applied on collophane flotation as depressant without disposing. • The industrial application indicates waste acid could replace part of H 2 SO 4 steadily. • Consumption of plenty waste acid brings considerable economic environmental benefits. • Depression mechanism was studied by solution chemistry calculation and SEM analysis. [ABSTRACT FROM AUTHOR]

In this paper, the particle interaction between the fine fluorite and quartz (all less than 10 μm) and its effect on the fluorite flotation were studied mainly by rheological measurements, optical observation and micro-flotation tests. Sodium oleate was used as the fluorite collector. The yield stress, which is a rheology parameter, was utilized to quantify the aggregation degree of the particles and evaluate the strength of the net-work structures in flotation slurry. The yield stress value of fine fluorite slurry as a function of the solid concentration, pH, percentage of the fine quartz and collector concentration was measured. The rheological measurements and the optical observation results show that the fluorite particles could partially aggregate into flocs in the pH range of 5–10 and form net-work structure in suspensions, while quartz particles could not aggregate across the whole pH range tested. When quartz and fluorite particles were mixed in water, the yield stress of the mixed mineral slurry was much higher than that of the single mineral slurry, demonstrating a strong hetero-coagulation between the two minerals. The flotation performance of the fine fluorite particles with different degree of hetero-coagulation (caused by the different percentage of fine quartz) was tested. The hetero-coagulation exhibited a detrimental effect on the fluorite flotation, manifesting as decreased flotation recovery and decreased flotation rate. It was found that the hetero-coagulation deteriorated the fine fluorite flotation by forming strong net-work structures that could interfere with the rising processes of the bubbles carrying valuable mineral particles. The research provides a new way for quantifying the particle interactions and may potentially be used for regulating the flotation operations in the fluorite flotation plants. Unlabelled Image • The yield stress of fluorite, quartz and their mixtures slurry (−10 μm) were measured. • The yield stress was used to quantify the aggregation degree of the mineral slurry. • Fluorite particles partially aggregated in the pH 5–10 while quartz dispersed. • There existed hetero-coagulation between the fluorite and quartz particles in water. • The hetero-coagulation resulted in deteriorated fine fluorite flotation. [ABSTRACT FROM AUTHOR]