Ailiang Chen

Synthesis of bioactive ceramic on the titanium substrate by micro-arc oxidation

Bioactive ceramic films on titanium substrate are prepared successfully by micro-arc oxidation in electrolyte solution containing NaOH only. The coatings are prepared by micro-arc oxidation at various applied current densities (200-400 mA/cm2) and in NaOH electrolyte with different concentrations. The XRD shows that they are composed of rutile, anatase, Na2Ti6O13, and Na2Ti4O9 phases. The composition and surface morphologies are strongly dependent on the applied current density and electrolyte concentration. For example, at high current density, the phase is mainly composed of rutile and Na2Ti6O13, and at high electrolyte concentration, it is Na2Ti6O13 phase. The morphologies of the samples vary with the increase of current and electrolyte concentration. The apatite-inducing ability of bioactive ceramic films is evaluated in biological model fluids. After soaking in biological model fluids, the titania-based coatings containing Na2Ti6O13 phase have excellent capability of inducing bone-like apatite.

Pulsed electrodeposition of hydroxyapatite on titanium substrate in solution containing hydrogen peroxide

Abstract Hydroxyapatitc(HAP) coatings were prepared on the titanium substrate in the electrolyte containing H 2 O 2 by the pulse electrodeposition. The introduction of H 2 O 2 restrains the evolution of H 2 and improves the adhesive strength between coatings and substrate. The results of pulse electrodeposition show that the relaxation time of the pulse is beneficial to growth of HAP because it makes ions diffuse from bulk to the surface of electrode and reduces concentration polarization in the next pulse time. It is beneficial to the increase of the duty circle of the pulse for deposition of HAP, but the result is not good if it is increased excessively. With increasing potential, it is good for the growth of HAP coatings. If the potential is too high, it is easy for HAP coatings to drop off during the process of electrodeposition under too intensive polarization, such as −1.0 V (vs SCE), and there is not many coatings on the substrate. The combination of pulse electrodeposition and addition of hydrogen peroxide can assuredly improve the physico-chemical properties of hydroxyapatite coatings.

Optimization of separation processing of copper and iron of dump bioleaching solution by Lix 984N in Dexing Copper Mine

Abstract The effects of the concentration of Lix 984N, phase ratio, initial pH value of aqueous phase and extraction time on the extraction of copper and iron under the condition of low Cu2+/Fe3+ ratio in dump bioleaching solution of Dexing Copper Mine were explored. The optimal conditions of extraction are as follows: the concentration of Lix 984N 10%; the phase ratio (O/A) 1:1; the initial pH value of aqueous phase 1.5 and the mixing time 2 min. The stripping experiments show that H2SO4 solution could efficiently recover copper from the organic phase under the optimal conditions.

Measurements of zinc oxide solubility in sodium hydroxide solution from 25 to 100 °C

Abstract The solubility of zinc oxide in sodium hydroxide solution was measured in a closed polytetrafluoroethylene vessel from 25 to 100 °C. The ZnO solubility was determined by employing the method of isothermal solution saturation. The results show that only ZnO solid exists in the equilibrium state in the low concentration alkali regions, and the solubility of zinc oxide is almost invariable with temperature. With the increase of alkali concentration, equilibrium solid turns from ZnO to NaZn(OH) 3 suddenly, this mutation is called invariant point, 3: 55ents on the X-ray intensities from Ti3-2aL ce dynamics of the compounds AlCo and AlNi []tweight. The alkali concentration of the invariant points increases with increasing temperature, but the solubility of NaZn(OH) 3 decreases with increasing alkali concentration at the same temperature. At the same Na 2 O concentration, the higher the temperature is, the higher the solubility of NaZn(OH) 3 is.

Thermodynamics and kinetics of adsorption of molybdenum blue with D301 ion exchange resin

Abstract The adsorption behavior of D301 for molybdenum blue was investigated. The thermodynamics parameters in adsorption process were calculated and the adsorption kinetics was studied. The experimental results show that the adsorption characteristic of D301 for molybdenum blue fits well with the Freundlich adsorption isotherm equation. In the adsorption process of D301 for molybdenum blue, both the enthalpy change Δ H and entropy change Δ S are positive, while the free energy change Δ G is negative when temperatures are in the range of 303-333 K. It is indicated that the adsorption is a spontaneous and endothermic process, and the elevated temperatures benefit to the adsorption. Kinetic studies show that the kinetic data are well described by double driving-force model, and the adsorption rate of molybdenum blue on D301 is controlled by the intraparticle diffusion during the adsorption process. The total kinetic equation is determined.

Thermodynamics analysis of LiFePO4 pecipitation from Li–Fe(II)–P–H2O system at 298 K

Abstract Thermodynamics of the precipitation from Li–Fe(II)–P–H2O system at 298 K was investigated. The results demonstrate that LiFePO4 can be formed at room temperature under pH value of 0–11.3, and the impurities Li3PO4 and Fe(OH)2 will be yielded at pH value above 11.3 and 12.9, respectively. The optimum pH value for LiFePO4 precipitation is 8–10.5. Considering the low rate of phase transformation kinetics, metastable Li–Fe(II)–P–H2O system was also studied. The results indicate that equimolar ratio of co-precipitation precursor Fe3(PO4)2·8H2O and Li3PO4 cannot be obtained at the initial molar ratio 1:1:1 and 1:1:3 of Li:Fe:P. In contrast, equimolar ratio of the co-precipitation precursor can be yielded by adjusting the pH value to 7–9.2, matching the molar ratio 3:1:1 of Li:Fe:P, meaning that Li+-excess is one of the essential conditions for LiFePO4 preparation by co-precipitation method.

Influence of earth gravity on reaction engineering of tubular reactor for high concentration tungsten ion-exchange

The influence of gravity on the reaction engineering of tubular reactor is studied by analyzing the residence time distribution curves. The results show that upflow-feeding mode is more beneficial compared with downflow-feeding mode, since the flow pattern of the fluid in the reactor is closer to plug flow. The result of dynamic experiment conducted in ion-exchange of tungsten metallurgy is as good as that in reaction engineering of ion-exchange column. Whether downflow-feeding or upflow-feeding mode is adopted, breakthrough time decreases when solution concentration increases. Upflow-feeding mode has longer breakthrough time and greater improvement in adsorption capacity especially with high WO3 concentration in ion-exchange.

Removal of copper from nickel anode electrolyte through ion exchange

Abstract An novel method for removal of copper from nickel anodic electrolyte through ion exchange was studied after cupric deoxidization. Orthogonal design experiments show the optimum conditions of deoxidizing cupric into Cu + in the nickel electrolyte are the reductive agent dosage is 4.5 times as the theoretic dosage and reaction time is 0.5 h at 40 °C and pH 2.0. Ion exchange experiments show that the breakthrough capacity( Y ) decreases with the increase of the linear flow rate( X ): Y =1.559–0.194 X + 0.006 7 X 2 . Breakthrough capacity increases with the increase of the ratio of height to radius(RRH). The higher the initial copper concentration, the less the breakthrough capacity(BC). SO 4 2i and nickel concentration have no obvious change during the process of sorption, so it is not necessary to worry about the loss of nickel during the sorption process. Desorption experiments show that copper desorption from the resin is made perfectly with NaCl solution added with 4% (volume fraction) H 2 O 2 (30%) and more than 100 g/L CuCl 2 solution is achieved.

Deep removal of copper from nickel electrolyte using manganese sulfide

Abstract Copper is difficult to separate from nickel electrolyte due to low concentration of copper (0.53 g/L) with high concentration of nickel (75 g/L). Manganese sulfide (MnS) was used to deeply remove copper from the electrolyte. Experimental results show that the concentration of copper ( ρ (Cu)) decreases from 530 to 3 mg/L and the mass ratio of copper to nickel ( R Cu/Ni ) in the residue reaches above 15 when the MnS dosage is 1.4 times the theoretical value D t,MnS ( D t,MnS =0.74 g) and the pH value of electrolyte is 4–5 with reaction time more than 60 min at temperatures above 60 °C. The concentration of newly generated Mn 2+ ( ρ (Mn)) in the solution is also reduced to 3 mg/L by the oxidation reaction. The values of ρ (Cu), ρ (Mn) and R Cu/Ni meet the requirements of copper removal from the electrolyte. It is shown that MnS can be considered a highly effective decoppering reagent.

Study of decomposing carbonyl slag

A new technology was put forward to deal with the carbonyl slag at low acidity and low oxygen pressure in the kettle. With the orthogonal experiments for analyzing the sequence of four factors and some single factor experiments for the best conditions. The best conditions are used for extracting nickel, cobalt and copper and enriching precious metals: the cupric ion concentration is 5 g/L; and pH=6; the sulfur coefficient is 1.4; the oxygen pressure is 0.08 MPa; the time bubbling oxygen is 20 min; the ratio of liquid to solid is 8:1; the leaching time is 2 h; the heating time is 2.5 h. The leaching rates of nickel and cobalt are more than 98% and that of copper is above 97%. Nickel and cobalt can be separated efficiently from copper and precious metals from the carbonyl slag. Moreover, its leaching liquor has less copper. Nickel and cobalt can be reclaimed only once. During the whole process, the leaching rates of Au and Ag are more than 99.9%, while other precious metals are still in the residue without any loss.