Effect of integration of mechanical ball milling and flue gas desulfurization gypsum on dealkalization of bauxite residue

The synergistic impact of mechanical ball milling and flue gas desulfurization(FGD)gypsum on the dealkalization of bauxite residue was investigated through integrated analyses of solution chemistry,mineralogy,and microtopography.The results showed a significant decrease in Na_(2)O content(>30 wt.%)of FGD gypsum-treated bauxite residue after 30 min of mechanical ball milling.Mechanical ball milling resulted in differentiation of the elemental distribution,modification of the minerals in crystalline structure,and promotion in the dissolution of alkaline minerals,thus enhancing the acid neutralization capacity of bauxite residue.5 wt.%FGD gypsum combined with 30 min mechanical ball milling was optimal for the dealkalization of bauxite residue.

Treatment of backwater in bauxite flotation plant and optimization by using Box-Behnken design

Flotation indexes gradually decrease with the increase of cycle time of the backwater in bauxite floatation,and discharge of backwater brings environmental risk.In this study,methods such as Fenton-oxidation,adsorption and coagulation were used in the treatment of backwater,the flotation indexes were checked after backwater treatments,and Box-Behnken design(BBD)was used in the optimization of the main operating parameters.The results reveal that flotation indexes are effectively improved after coagulation treatment by polyaluminum ferric chloride(PAFC).The optimum parameters predicted by BBD are pH 7.55,1.09 g/L PAFC dosage and temperature of 25℃.Under these optimum conditions,a maximum recovery of Al2O3 of 82.83%and a minimum A/S of 1.30 of tailings are gained,while the deviations are less than 3%from the predicted values.These findings encourage the application of BBD for the optimization of critical parameters in backwater treatment.

Microstructure and texture evolution in LZ91 magnesium alloy during cold rolling

LZ91 magnesium alloy extruded sheets were subjected to cold rolling.The microstructure and texture evolution were tracked using optical microscopy(OM)and X-ray diffraction(XRD).Theα-Mg andβ-Li phases were elongated along rolling direction(RD),contributing to the formation of a thin lamellar“sandwich”structure.This“sandwich”structure is favored for glissile dislocation ofα-Mg phase during rolling.Theα-Mg andβ-Li phases are near Burgers orientation relationship,resulting in an unusual RD texture component in(0002)pole figure.

Microstructure and electrolysis behavior of self-healing Cu-Ni-Fe composite inert anodes for aluminum electrowinning

The microstructure evolution and electrolysis behavior of(Cu_(52)Ni_(30)Fe_(18))–x Ni Fe_2O_4(x=40wt%,50wt%,60wt%,and 70wt%)composite inert anodes for aluminum electrowinning were studied.Ni Fe_2O_4 was synthesized by solid-state reaction at 950°C.The dense anode blocks were prepared by ball-milling followed by sintering under a N_2 atmosphere.The phase evolution of the anodes after sintering was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy.The results indicate that a substitution reaction between Fe in the alloy phase and Ni in the oxide phase occurs during the sintering process.The samples were also examined as inert anodes for aluminum electrowinning in the low-temperature KF–NaF–AlF_3 molten electrolyte for 24 h.The cell voltage during electrolysis and the corrosion scale on the anodes were analyzed.The results confirm that the scale has a self-repairing function because of the synergistic reaction between the alloy phase with Fe added and the oxide phase.The estimated wear rate of the(Cu_(52)Ni_(30)Fe_(18))–50Ni Fe_2O_4 composite anode is 2.02 cm·a^(-1).

Bubble behavior in aluminum reduction cell with inert anode

The bubble behavior is one of the key factors for the design and the process of aluminum reduction cell using inert anode.A see-through cell is constructed to investigate the bubble flow behavior and the electrolyte flow pattern induced by bubbles.The test results show that the electrolyte is driven by the bubble to move around the cathode,and also some vortices occur in local areas.The bubble generated at the anode bottom undergoes the processes of formation,growth,sliding,detachment and coalescence.However,the bubble generated at the middle of anode detaches rapidly from the anode surface and moves upward and collides with other bubbles,which results in coalescence or break-up.Most bubbles are released into the atmosphere at the liquid surface,while some other bubbles taken by the electrolyte flush to the height higher than the mean horizontal level of the liquid and then drop down and move horizontally and they are released finally.Some bubbles are kept unbroken and are sliding on the electrolyte surface.The diameter of bubble generated at inert anode is smaller than that of bubble generated at graphite anode.Moreover,the bubbles on inert anode are spherical,which was different from those in tubular or disk form on graphite anode.

Synthesis and characterization of a novel collector for the desulfurization of fine high-sulfur bauxite via reverse flotation

Bauxite is one of the main raw materials in the alumina industry.Fine high-sulfur bauxite flotation desulfurization is a great challenge presently.This study aims to synthesize nanoparticle collectors(NPCs)by emulsion polymerization to improve the abovesaid flotation desulfurization process.The physicochemical properties of high-sulfur bauxite were analyzed,and the experimental conditions for the synthesis of NPCs were optimized.The interaction mechanism between NPCs and pyrite was studied via fundamental analyses including SEM(Scanning Electron Microscope),FT-IR(Fourier Transform Infrared spectoscopy),Zeta-potential,XPS(X-ray Photoelectron Spectroscopy),and wettability.Under the closed-circuit flotation flowsheet of"one roughing-two cleaning-three scavenging",aluminum concen-trate with a yield of 85.91%and sulfur content of 0.56%were obtained using a common collector.However,with the addition of the novel NPC,aluminum concentrate with a yield of 85.70%and sulfur content of 0.36%could be obtained by a simpler flowsheet of"one roughing-one cleaning-two scav-enging".The improvement in flotation performance is suggested to be contributed by the addition of spherical NPC,which induced a rougher and more hydrophobic pyrite surface.