i-ping Hu

Leaching kinetics of low-grade copper ore containing calcium-magnesium carbonate in ammonia-ammonium sulfate solution with persulfate

The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentrations of ammonia, ammonium sulfate and sodium persulfate were determined. The results show that the leaching rate is nearly independent of agitation above 300 r/min and increases with the increase of temperature, concentrations of ammonia, ammonium sulfate and sodium persulfate. The EDS analysis and phase quantitative analysis of the residues indicate that bornite can be dissolved by persulfate oxidization. The leaching kinetics with activation energy of 22.91 kJ/mol was analyzed by using a new shrinking core model (SCM) in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. A semi-empirical rate equation was obtained to describe the leaching process and the empirical reaction orders with respect to the concentrations of ammonia, ammonium sulfate and sodium persulfate are 0.5, 1.2 and 0.5, respectively.

Solvent Extraction of Copper and Ammonia from Ammoniacal Solutions Using Sterically Hindered β-diketone

Extraction of copper and ammonia from Cu(superscript 2+)-NH3-Cl(superscript -)-H2O solution using laboratorialy synthesized sterically hindered β-diketone (4, 4-dimethyl-1-(4-dodecylphenyl)-1, 3-pentanedione) was studied. The effects of the copper concentration, the total ammonia concentration, the initial pH in the aqueous phase, the phase ratio, and the temperature on copper extraction ratio and ammonia extraction in loaded organic phase were investigated using this sterically hindered β-diketone. Under the conditions of temperature 25℃, contact time of two phases 30 min, phase ratio 1:1, concentration of copper 3 g/L, concentration of total ammonia 3 mol/L, aqueous pH 8.43, and the concentration of β-diketone in organic phase 20% (volume fraction), ammonia in aqueous phase is much lower to be extracted by organic phase (just 14.5 mg/L), while the extraction rate of copper is 95.09%.

Preparation, characterization and photo-catalytic behavior of WO3-TiO2 catalysts with oxygen vacancies

Abstract TiO 2 photocatalysts compounded with WO 3 were prepared via a modified hydrolysis process and the 2% WO 3 -TiO 2 catalysts with different oxygen vacancies were obtained by calcination at 873 K in H 2 atmosphere. The catalysts were identified using X-ray diffractometry (XRD), specific surface measurement (BET), electron paramagnetic resonance spectroscopy (EPR), UV-Vis diffusion refraction spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of 2% WO 3 -TiO 2 with different oxygen vacancies was investigated employing splitting of water for O 2 evolution. The results indicate that appropriate oxygen vacancies can obviously improve the photocatalytic activity of 2% WO 3 -TiO 2 catalysts, and using Fe 3+ as an electron acceptor under UV irradiation in 12 h, the maximum rate for O 2 evolution is 667 µmol/(L·h).

Effects of mechanical activation and oxidation-reduction on hydrochloric acid leaching of Panxi ilmenite concentration

Abstract The effects of oxidation-reduction treatment and mechanical activation on the hydrochloric acid leaching performance of Panxi ilmenite concentration were investigated. The results show that both of oxidation-reduction treatment and mechanical activation significantly accelerate the extraction of Fe, Ca and Mg from Panxi ilmenite concentration; however, the CaO and MgO contents of the calcined residues obtained from oxidized-reduced ilmenite concentration are higher than the standard values required by chlorination process. The Ca and Mg in oxidized-reduced ilmenite concentration can be leached much faster after mechanical activation, yielding a synthetic rutile which meets the requirements of chlorination process containing 90.50% TiO 2 and 1.37% total iron as well as combined CaO and MgO of 1.00%. The optimum oxidation and reduction conditions are as follows: oxidization at 900 °C in the presence of oxygen for 15 min and reduction at 750 °C by hydrogen for 30 min.

Synergistic extraction of zinc from ammoniacal solutions using β-diketone mixed with CYANEX923 or LIX84I

Abstracts The extraction behaviors of zinc from ammoniacal solutions were investigated using β-diketone (HA) and their mixtures with CYANEX923 or LIX84I. The effects of pH, total ammonia concentration, extractant concentration, anion species and temperature on zinc extraction were examined. The synergistic mechanism was discussed with regard to the structure of extractant and the extracted zinc complexes. It is found that the increase of total ammonia concentration and pH inhibits zinc extraction for all extraction systems due to the formation of zinc ammine complexes in aqueous phase. This effect of HA with CYANEX923 is evidently smaller than that of HA with LIX84I or HA alone system. Effect of anion species on the zinc extraction by HA with CYANEX923 can be neglected, but this effect of HA alone and the mixture of HA with LIX84I decreases in the order of (NH 4 ) 2 SO 4 > NH 4 NO 3 > NH 4 Cl.

Recovery of copper from simulated ammoniacal spent etchant using sterically hindered beta-diketone

Abstract The solvent extraction of copper from simulated ammoniacal spent etchant with 1-(4′-dodecyl)-phenyl-3-tertiary butyl- 1, 3-octadione (HR) was studied, and a model of extraction isotherm was proposed and verified with equilibrium extraction constant. The influence of equilibration time, extractant concentration and phase ratio on the extraction of copper was studied at (298±0.5) K. For the spent etching solutions containing 112.98 g/L Cu, 6 mol/L NH 3 and 1 mol/L NH 4 + , the optimal solvent extraction condition of copper was obtained in one-stage solvent extraction at phase ratio of 5:4 with 40% HR in sulphonated kerosene for 5 min. The copper concentration in the raffinate decreased to 63.24 g/L and raffinate can be favorably recycled to the etching solution. The stripping studies were carried out with the simulated copper spent electrolyte containing 30 g/L Cu and 180 g/L H 2 SO 4 . The stripping ratio is 98.27% from the loaded organic phase after one-stage stripping at phase ratio of 1:2 at (298±0.5) K.

Effects of Na4EDTA and EDTA on seeded precipitation of sodium aluminate solution

Na4EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of sodium aluminate solution, particle size distribution (PSD) and morphology of precipitated gibbsite were investigated using titration method, particle size analyzer and scanning electron microscope (SEM), respectively. The results show that the two additives can accelerate the seeded precipitation rate of sodium aluminate solution. At relatively high concentration, the facilitative effect of EDTA on sodium aluminate solution is more obvious than that of Na4EDTA. EDTA makes gibbsite particles thinner than Na4EDTA. The Na+ and H+ result in the different effects on the seeded precipitation rate of sodium aluminate solution in spite of the same EDTA anion in the two additives.

Preparation, characterization and photocatalytic behavior of WO3-TiO2/Nb2O5 catalysts

TiO2/Nb2O5 photocatalyst loaded with WO3 (WO3-TiO2/Nb2O5) was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiO2/Nb2O5 by using Fe3+ as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 µmol/(L·h).

Solubility of hemimorphite in ammonium sulfate solution at 25 °C

Abstract The solubility of natural hemimorphite in ammonium sulfate solution was measured by isothermal solution method at 25 °C and the dissolved residue of hemimorphite was investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) methods. The results show that zinc and silica in hemimorphite simultaneously dissolve in ammonium sulfate solution. The solubility of zinc in solution increases rapidly from 4.5381 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 11.5083 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The solubility of silica in solution increases slowly from 2.5509 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 7.2891 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The dissolved residue is the characteristic of hemimorphite Zn 4 Si 2 O 7 (OH) 2 ·H 2 O based on the results of the XRD, SEM and FTIR. Thus, no phase transition occurs in the dissolution process of hemimorphite in ammonium sulfate solution.

Combined Effect of Amino and Carboxyl Group in α-alanine on Seeded Precipitation of Sodium Aluminate Solution

α-alanine was adopted as a new additive to elucidate the seeded precipitation mechanism of sodium aluminate solution. α-alanine has the inhibitory effect at the initial period of reaction, but the favorable effect in subsequent reaction. The combined effect of amino and carboxyl group in α-alanine was confirmed by investigating the effect of propionic acid, ethamine and the mixture of propionic acid and ethamine (mole ratio 1:1) on the precipitation of sodium aluminate solution, respectively. The inhibitory effect derives from the adsorption of amino or carboxyl group in α-alanine on the active surface sites of gibbsite, which was confirmed by the alleviating inhibitory effects of propionic acid, ethamine and α-alanine due to the double crystal seed mass. The semi-quantitative IR spectrum analysis of the relative concentrations of Al2O(OH)6(superscript 2-) with the band at about 550 cm^(-1) and polynuclear aluminate ion with the bands at about 880 cm^(-1) and 635 cm^(-1), indicates that the dynamic balance among some aluminate species present in sodium aluminate solution is broken due to the addition of α-alanine, thus resulting in the change of the seeded precipitation ratio of sodium aluminate solution.