Solution chemistry of carbonate minerals and its effects on the flotation of hematite with sodium oleate

The effects of carbonate minerals（dolomite and siderite） on the flotation of hematite using sodium oleate as a collector were investigated through flotation tests, supplemented by dissolution measurements, solution chemistry calculations, zeta-potential measurements, Fourier transform infrared（FTIR） spectroscopic studies, and X-ray photoelectron spectroscopy（XPS） analyses. The results of flotation tests show that the presence of siderite or dolomite reduced the recovery of hematite and that the inhibiting effects of dolomite were stronger. Dissolution measurements, solution chemistry calculations, and flotation tests confirmed that both the cations（Ca^（2＋） and Mg^（2＋）） and CO_3^（2＋）ions dissolved from dolomite depressed hematite flotation, whereas only the 23CO-ions dissolved from siderite were responsible for hematite depression. The zeta-potential, FTIR spectroscopic, and XPS analyses indicated that Ca^（2＋）, Mg^（2＋）, and CO_3^（2-）（HCO_3^-） could adsorb onto the hematite surface, thereby hindering the adsorption of sodium oleate, which was the main reason for the inhibiting effects of carbonate minerals on hematite flotation.

SOLUTION CHEMISTRY OF SALT TYPE MINERAL FLOTATION

Solution chemical equilibria involving flotation agents(hereafter llotagents),minerals and solution play a crucial role in determining the behavior of complex flotation systems.Salt-type minerals such as calcite,apatite etc are sparingly soluble in aqueous solution and form dissolved mineral species in bulk solution.It has been found that such dissolved species interact with the minerals,and often lead to surface conversion of the minerals.In addition,they can interact with various llotagents and lead to surface or bulk precipitation and loss of selectivity in the flotation.Relevant solution equilibria of these salt-type minerals and their interactions with conventional and structurally modified reagents are discussed.Better selectivity in their flotation can be achieved by controlling such interactions and manipulating the solution chemical equilibria.

EFFECT OF SOLUTION CHEMISTRY ON THE FLOTATION SEPARATION OF WOLLASTONITE FROM QUARTZ

This paper deals with the flotation separation of wollas-tonite from quartz by using Na-oleate as a collector and metallic ion as an activator. The reasons why wollastonite is difficult to separate from quartz using Na-oleate as a collector have been studied. It is found that quartz does not float well in a mixture of wollastonite and quartz because of the solution chemistry effect in a wollastonite suspension. The compositions of the wollastonite suspensions have been studied, and the?potential of the two minerals have been determined to explain the solution chemistry effects on the flotation of the respective minerals.

STUDY ON SOLUTION CHEMISTRY BETWEEN TANNIC ACID AND THE FLOTATION PULP OF WOLLASTONITE AND DIOPSIDE

The mechanisms of interaction between tannic acid and calcium ions either added externally to or inherently present in the (?)olution ( dissociated from mineral surface ) , are studied by the use of Inductively Coupled Plasma Atomic Emission Spectroscopy ( ICP-AES ) , Ultraviolet Spectroscopy (UV). It is found that wollastonite has a high solubility in the concentration of calcium ions, calcium ions are able to interact with tannic acid.

Effect and mechanism of siderite on reverse flotation of hematite

The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier transform infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite significantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek（DLVO） theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calculations indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO_3 precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite.

Shape-controlled Synthesis of Porous SnO_2 Nanostructures via Morphologically Conserved Transformation from SnC_2O_4 Precursor Approach

Porous SnO_2 nanostructures with controlled shapes were synthesized by a facile morphologically conserved transformation from Sn C_2O_4 precursor approach. Well-defined Sn C_2O_4 nanostructures can be obtained through a solution-based precipitation process at ambient conditions without any surfactant. The formation mechanism of such microstructures was tentatively proposed on the basis of intrinsic crystal structure and the reaction conditions. We found that the morphologies of precursor were well maintained while numerous pores were formed during the annealing process. The combined techniques of X-ray diffraction, nitrogen absorption–desorption, field emission scanning electron microscopy, and(high-resolution) transmission electron microscopy were used to characterize the as-prepared SnO_2 products. Moreover, cyclic voltammetry(CV) study shows that the shape of CV presents a current response like roughly rectangular mirror images with respect to the zero-current line without obvious redox peaks, which indicating an ideal capacitive behavior of the SnO_2 electrodes. The photoluminescence(PL) spectrum study suggests that the as-obtained porous SnO_2 nanostructures might have a large number of defects, vacancies of oxygen, and local lattice disorder at the interface, interior and exterior surfaces.

Molecular mechanism of crystal nucleation from solution

Nucleation from solution is fundamental to many natural and industrial processes.The understanding of molecular mechanism of nucleation from solution is conducive to predict crystal structure,control polymorph and design desired crystal materials.In this review,the nucleation theories,including classical nucleation theory(CNT),nonclassical nucleation theory,as well as other new proposed theories,were reprised,and the molecular mechanism of these theories was compared.Then,the molecular process of nucleation,including the current study techniques,the effect of molecular self-assembly in solutions,desolvation process,as well as the properties of solvent and crystal structure on nucleation from solution were summarized.Furthermore,the relationship of molecular conformation in solution and in crystal,and the effect of solute molecular flexibility on nucleation were discussed.Finally,the current challenges and future scopes of crystal nucleation from solution were discussed.

A New Route for the Rapid Synthesis of Metal–Organic Frameworks at Room Temperature

Rapid synthesis of metal–organic frameworks(MOFs),especially high-valence MOFs at roomtemperature without external energy,is a challenging topic.In this work,a stable radical solution has been discovered.Various MOFs with versatile metal nodes and ligands were rapidly synthesized at room temperature in the absence of external energy.Especially,MOFs with conjugated ligands achieved instantaneous architecture(in less than 1 s)and quantitative yield.Radicals in the solution play a crucial role in the accelerated kinetics,and the new radical route paves a cyclic pathway for the MOF synthesis.The mechanism has been thoroughly investigated by electron paramagnetic resonance,in situ proton nuclear magnetic resonance,X-ray absorption spectra,in situ small-angle X-ray scattering-wide-angle X-ray scattering,and density functional theory calculations.