Synthesis and kinetic analysis of hydromagnesite with different morphologies by nesquehonite method

514-521Hydromagnesite with different morphologies has been synthesized using self-made nesquehonite whiskers as raw materials. The synthesized samples have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that porous rod-like hydromagnesite are generated at 328~353K and in the pH value of 9.30+0.2, while irregular flower-like and flat layered ones are synthesized in the pH values of 10.0+0.05 and 11.0+0.05, respectively. The yield of hydromagnesite improved linearly with the increase of the temperatures and solution pH values. Porous rod-like hydromagneiste crystals with good crystalline and uniform morphology are obtained when the pyrolysis time is over 60 min. Furthermore, the apparent activation energy of phase transformation is calculated to be 3.4080 kJ/mol. According to the results, the experimental data can be well described by the kinetic model, suggesting that the phase transfer rate is dependent on the temperature

Study on Reverse Flotation Process of Magnesite and Dolomite in Dodecylamine System

Through the single mineral flotation test, the flotation behavior of magnesite and dolomite in the dodecylamine flotation system and the influence of the regulator Fe3+ on the floatability of the two minerals were studied. Based on Fourier Infrared Spectroscopy (FTIR) and contact angle test, the mechanism of Fe3+ was studied. The flotation test results show that in the dodecylamine system, under the natural pH condition of the pulp, the floatability of dolomite is better than that of magnesite. There is a certain floatation difference between magnesite and dolomite, and the addition of a small amount of Fe3+ significantly improves the floatation difference of the two minerals. Infrared spectroscopy test results show that the adsorption of dodecylamine on the surface of dolomite is mainly electrostatic adsorption, dolomite CO32− out-of-plane bending vibration and CO32− in-plane bending vibration are almost unchanged, and -CH3 and -CH2 are symmetrical and asymmetrical. The peak value of extensional vibration increases. The contact angle test results show that the addition of a small amount of Fe3+ enhances the hydrophobicity of dolomite, which has the effect of activating dolomite

Characterization of Slag Reprocessing Tailings-Based Geopolymers in Marine Environment

In this study, copper slag reprocessing tailings (CSRT) were synthesized into geopolymers with 40%, 50% and 60% metakaolin. The evolution of compressive strength and microstructures of CSRT-based geopolymers in a marine environment was investigated. Except for compressive strength measurement, the characterizations of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) were included. It was found that marine conditions changed the Si/Al ratio in the sodium-aluminosilicate-hydrate (N-A-S-H) gel backbone, promoted the geopolymerization process, led to more Q4(3Al), Q4(2Al) and Q4(1Al) gel formation and a higher compressive strength of the geopolymers. This provided a basis for the preparation of CSRT-based geopolymers into marine concrete

Mechanism of ultrasonic cavitation to improve the effect of siderite on quartz flotation

In order to effectively eliminate the effect of fine carbonate minerals on quartz flotation, the influence of fine siderite on quartz flotation was studied as well as the mechanism or role of ultrasonic treatment in the process. The results of adsorption capacity measurement and flotation solution chemical calculation show that fine siderite and its dissolved components have a great influence on the collector consumption and the surface properties of quartz. In addition, SEM, EDS and XPS analysis were used to study the surface morphology and chemical environment changes of quartz with and without ultrasonic treatment. The results of flotation test show that the recovery of quartz increase from 38.79% to 58.38% under the condition that ultrasonic time was 0.5 min and ultrasonic power was200 W. The mechanical effect caused by ultrasonic cavitation can clean the quartz surface to a certain extent and increase its active sites, thus improving the floatability of quartz

Effect and mechanism of citric acid on flotation separation of siderite and hematite

Heterocoagulation can occur between fine siderite and hematite particles, which would result in the low efficiency of their separation during the flotation process. To date, there have been no mature methods to increase their separation efficiency. In this paper, citric acid was used as a regulator to enhance the slurry dispersion efficiency. Micro-flotation, scanning electron microscopy (SEM) analysis, settling tests, particle size measurements, zeta potential measurements and E-DLVO theoretical calculations were conducted in the investigations. A maximum recovery difference (53.98%) between siderite and hematite in their mixtures flotation was obtained. Settling tests confirmed that citric acid contributed to improving the dispersion degree of the slurry. SEM analysis indicated that citric acid could clean the surface of particles and weaken the coagulation between siderite and hematite, which were in line with the results of particle size measurements. The zeta potential measurements and Extended-Derjaguin-Landau-Verwey-Overbeek (E-DLVO) theoretical calculations indicated that the citric acid could adsorb on the siderite and hematite surfaces and decreased the surface charge, resulting in a visible increase of the repulsion energy between siderite and hematite particles. Therefore, citric acid can be applied to remove the easily-ground carbonate minerals first to improve the flotation performance of hematite in the separation process of carbonate-containing iron ores

Separation of magnesite and calcite based on flotation solution chemistry

The dissolution characteristics of minerals, dissolution of flotation agents in solutions, and equilibrium of dissociations and associations serve as the basis for determining the optimal conditions for the effective components of flotation agents and for evaluating the interaction between flotation agents and minerals. This basis provided the theoretical support for the flotation separation of minerals. Based on this, the flotation separation of magnesite and calcite was realized using sodium dihydrogen phosphate, also known as monosodium phosphate (MSP), as a regulator and dodecylamine (DDA) as a collector. When MSP was used in the DDA system, single-mineral and binary mixed-ore flotation tests revealed that the floatability of calcite was significantly greater than that of magnesite and the separation of magnesite and calcite was more effective, respectively. Zeta potential measurements showed that MSP-containing negative groups could selectively reduce the zeta potential of calcite and promote the adsorption of DDA-containing positive groups on the surface of the calcite. However, this effect was negligible on the zeta potential of magnesite. Due to the stronger affinity of MSP to Ca2+ than that to Mg2+, as demonstrated by Fourier transform infrared and X-ray photoelectron spectroscopy analyses, the MSP was adsorbed onto the surface of calcite primarily by hydrogen bonds rather than magnesite, which promoted the stronger adsorption of DDA-containing positive groups on the surface of the calcite. As a result, the differences in the floatability of magnesite and calcite were enlarged by MSP. Thus, MSP can be utilized an effective regulator for the efficient separation of magnesite from calcite via reverse flotation

Strengthening Sulfidation Flotation of Hemimorphite via Pretreatment with Pb2+

The conventional sulfidation-xanthate flotation process that consists of sulfidization with sodium sulfide, activation by heavy-metal ions, and collection with xanthate is not sufficiently efficient for treating hemimorphite, and the dosages of the sulfurizing reagent and metal ions are large. In this study, the sulfidation flotation (Pb2+ + Na2S + Pb2+ + xanthate) of hemimorphite was strengthened by pretreating with Pb2+ before sulfidation. Microflotation test results indicated that the recovery of hemimorphite increased by 5–10% after pretreatment with Pb2+. The comprehensive results of adsorption experiments, scanning electron microscopy–energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy indicated that a large amount of Pb2+ was adsorbed on the hemimorphite surface and entered the lattice, forming Zn(4−x)PbxSi2O7(OH)2·H2O. The newly formed component had an increased amount of surface sulfidation active sites and had the effect of induced crystallization, making the surface more effective for sulfidation. After the Pb2+ was added to the pulp, a large number of uniform and dense PbS species were formed on the hemimorphite surface, increasing the number of adsorption sites for xanthate and reducing the competitive adsorption of residual S2− on the xanthate

Study of the Mechanism of the Fe-BHA Chelates in Scheelite Flotation

Scheelite associated with calcium-containing minerals such as calcite and fluorite is difficult to separate by flotation because of the Ca ions contained in the mineral lattices, which cause scheelite to have similar surface properties and floatability to gangue minerals. Traditional collectors such as oleic acid need to add a large amount of sodium silicate as gangue inhibitors, which causes difficulties for the settlement of tailings. In addition, the use of benzohydroxamic acid (BHA), which needs the addition of Pb(NO3)2 as the scheelite activator, can also cause environmental pollution. In this paper, Fe-BHA, a new collector containing the iron complex, was studied to investigate its flotation ability of scheelite, as well as its BHA/FeCl3 ratio on scheelite flotations. In the single mineral flotations, the Fe-BHA showed a significant difference in the flotation recoveries of scheelite and calcite, with a scheelite recovery of 77.03% at pH 8.0 and calcite recovery of 16.69% at the same pH. The results of the roughing tests of Xianglushan actual ore showed that the scheelite with Fe-BHA (500 g/t BHA and 200 g/t FeCl3) and 40 g/t oleic acid as collectors obtained satisfactory flotation results with a WO3 grade of 1.56% and WO3 recovery of 65.52%, which were much higher than those of scheelite with BHA or oleic acid as the collector, but there was still a gap with those of scheelite using Pb(NO3)2 as activation and BHA as the collector. The UV-Vis curves of the Fe-BHA with different BHA/FeCl3 ratios indicated that the Fe-BHA chelates might have several different structural forms, and the single mineral tests of the BHA/FeCl3 ratios showed that when the molar ratio of benzohydroxamic acid to FeCl3 was about 1.2:1, the best scheelite flotation result was obtained in this test. In addition, the XPS analyses proved that the adsorption of the Fe-BHA on the scheelite surface occurred, and by fitting the peaks of Ca 2p and O 1s of scheelite, it was found that the mechanism of the Fe-BHA acting on the Ca sites of the scheelite surface was through the removal of H2O from the Ca-OH of scheelite and Fe-OH from Fe-BHA to form Fe-O-H

Study of the Mechanism of the Fe-BHA Chelates in Scheelite Flotation

Scheelite associated with calcium-containing minerals such as calcite and fluorite is difficult to separate by flotation because of the Ca ions contained in the mineral lattices, which cause scheelite to have similar surface properties and floatability to gangue minerals. Traditional collectors such as oleic acid need to add a large amount of sodium silicate as gangue inhibitors, which causes difficulties for the settlement of tailings. In addition, the use of benzohydroxamic acid (BHA), which needs the addition of Pb(NO3)2 as the scheelite activator, can also cause environmental pollution. In this paper, Fe-BHA, a new collector containing the iron complex, was studied to investigate its flotation ability of scheelite, as well as its BHA/FeCl3 ratio on scheelite flotations. In the single mineral flotations, the Fe-BHA showed a significant difference in the flotation recoveries of scheelite and calcite, with a scheelite recovery of 77.03% at pH 8.0 and calcite recovery of 16.69% at the same pH. The results of the roughing tests of Xianglushan actual ore showed that the scheelite with Fe-BHA (500 g/t BHA and 200 g/t FeCl3) and 40 g/t oleic acid as collectors obtained satisfactory flotation results with a WO3 grade of 1.56% and WO3 recovery of 65.52%, which were much higher than those of scheelite with BHA or oleic acid as the collector, but there was still a gap with those of scheelite using Pb(NO3)2 as activation and BHA as the collector. The UV-Vis curves of the Fe-BHA with different BHA/FeCl3 ratios indicated that the Fe-BHA chelates might have several different structural forms, and the single mineral tests of the BHA/FeCl3 ratios showed that when the molar ratio of benzohydroxamic acid to FeCl3 was about 1.2:1, the best scheelite flotation result was obtained in this test. In addition, the XPS analyses proved that the adsorption of the Fe-BHA on the scheelite surface occurred, and by fitting the peaks of Ca 2p and O 1s of scheelite, it was found that the mechanism of the Fe-BHA acting on the Ca sites of the scheelite surface was through the removal of H2O from the Ca-OH of scheelite and Fe-OH from Fe-BHA to form Fe-O-H