Yasuhiro Fukunaka

Effect of hydrolysed metal cations on the liquid–liquid extraction of silica fines with cetyltrimethylammonium chloride

Abstract Silica fines of 2 O systems indicate that decreases in percentage recoveries of the silica in the lower pH range are in line with increases in concentrations of the metal hydroxo complexes. Furthermore, the silica depression disappears when the pH approaches the point-of-zero charge of the hydroxide precipitate. In these pH ranges, the neutral to negative metal precipitates are also extracted into the oil–water interface during the liquid–liquid extraction. It seems that the lipophilic-to-hydrophobic transition, that is, depression by metal-salt addition of silica fines in cationic liquid–liquid extraction is controlled by the presence of metal-hydroxide species and their charges, attributable to the hydroxide coating on the silica surface.

Desulfurization kinetics of molten copper by gas bubbling

Molten copper with 0.74 wt pct sulfur content was desulfurized at 1523 K by bubbling Ar-O2 gas through a submerged nozzle. The reaction rate was significantly influenced not only by the oxygen partial pressure but also by the gas flow rate. Little evolution of SO2 gas was observed in the initial 10 seconds of the oxidation; however, this was followed by a period of high evolution rate of SO2 gas. The partial pressure of SO2 gas decreased with further progress of the desulfurization. The effect of the immersion depth of the submerged nozzle was negligible. The overall reaction is decomposed to two elementary reactions: the desulfurization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of sulfur and oxygen contents in the melt and the SO2 partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model combined with the reported thermodynamic data of these reactions. Based on the present model, it was anticipated that the oxidation rate around a single gas bubble was mainly determined by the rate of gas-phase mass transfer, but all oxygen gas blown into the melt was virtually consumed to the desulfurization and dissolution reactions before it escaped from the melt surface.

The role of hydrolyzed metal cations in the liquid-liquid extraction of ultrafine silica with dodecyl sulfate☆

Abstract As part of a fundamental study on the recovery of fine particles, ultrafine silica was liquid-liquid extracted with the anionic collector sodium dodecyl sulfate (SDS). Isooctane and water were used as the two liquid phases. The pH dependence of the recovery level of the silica was determined in the absence and presence of metal salts, such as Fe(III), Al(III) and La(III), for physicochemical interpretation on the role of the hydrolyzed metal species during the anionic liquid-liquid extraction of the silica fines. The results showed that the silica could not be recovered without the metal salts, while the addition of the metal salt led to a significant increase in recovery in a certain pH range. Comparison of these results and the distribution diagrams of the metal species indicated that the increase in recovery is in line with the formation of metal hydroxides, hydroxo complexes and precipitates. Also, the minimum extraction edges of the silica in terms of pH were correlated to the residual concentration of the respective metal species in the water phase; the hydroxo complexes that form prior to the precipitation pH were the species responsible for the silica activation as well.

Interferometry Measurement of Concentration Profile of Cu 2+ Ions Associated with Electrodeposition of Copper under Microgravity

Copper was galvanostatically electrodeposited from 0.9M CUSO 4 solution contained in a quasi two-dimensional cell of effective thickness of 210 μm for 7 seconds during free falling in the drop shaft. The time variation of diffusion boundary layer thickness was measured in-situ with a common path type of microscopic interferometry and the diffusivity of Cu 2+ ions was estimated as 4 × 10 −6 cm 2 sec −1 . Under the gravitational field, the diffusion layer thickness developed much faster from 2 seconds after starting the electrodeposition than that under microgravity.

Non-isothermal Oxidation of Copper Concentrate Particles Falling in a Vertical Tube. Effect of composition on the interfacial reaction rate of copper concentrate.

Four kinds of copper concentrate of different compositions were oxidized in N2-O2 gas stream. The dependence of the desulphurization reactions on oxygen partial pressure and wall temperature was examined. X-ray diffraction pattern analysis of the cinders showed that copper concentrate was thermally decomposed, and the FeS formed simultaneously was oxidized to Fe2O4. The non-isothermal oxidation of copper concentrate particles was described using an unreacted core model of copper concentrate covered with an outer product layer of magnetite. The frequency factor k0 of the interfacial reaction rate constant was determined so as to fit the calculated desulphurization curve to the observed curve. It was found that the k0 value significantly decreased with an increase of pO2. Moreover, k0 for CuFeS2 was larger and it decreased with the amount of FeS2 contained in the copper concentrate.