Hu Yuehua

The effect of silver-bearing catalysts on bioleaching of chalcopyrite

Abstract The effect of silver ion, silver sulfide and silver-bearing concentrate (Ag–C) on the bioleaching of chalcopyrite has been investigated. It has been found that the addition of silver-bearing catalyst greatly enhanced copper dissolution from chalcopyrite and copper ores. The dissolved copper from chalcopyrite ore was increased from 25% to 75%, 65% and 67%, respectively, by addition of 0.32 g Ag, 4 g argentite (Ag 2 S) and 20 g Ag–C, per kilogram of ore after 20-day bioleaching in shake flasks. The bioleaching tests for a column charged with 18 kg chalcopyrite-containing waste rock showed that the copper extraction increased from 3.4% to 21.7% and 16.5%, respectively, by using 0.21 g Ag 2 S and 15 g Ag–C per kilogram of rock. The results indicated the possibility of using silver-bearing concentrate as an effective and cheap catalyst for bioleaching of chalcopyrite ore instead of the expensive silver. The mechanism of enhancement of chalcopyrite bioleaching in these systems was discussed, based on the “mixed potential model”, the mineralogy of silver-bearing concentrate as well as by using X-ray diffraction and electrochemical measurement.

Research and application of bioleaching and biooxidation technologies in China

This paper presents some of the investigations of bioleaching and biooxidation applications in China. Bioleaching and biooxidation are new technologies with great potentials due to their simplicity, low operating cost, and little pollution to the environment. To date, two heap bioleaching plants and two biooxidation plants have been successfully put into operation to process copper ores and refractory gold concentrates, respectively. Investigations of applying bioleaching and biooxidation for other metal and non-metal resources are now being carried out.

Effects of sodium hexmetaphosphate on flotation separation of diaspore and kaolinite

In order to offer high grade concentrate to produce alumina by Bayer, the reverse-flotation technology of bauxite was investigated. The results show that sodium hexmetaphosphate has different depression on the flotation of diaspore and kaolinite. The recoveries of diaspore decrease markedly with the increase of the concentration of sodium hexmetaphosphate with dodecyl-amine as collector. Fourier transform infrared spectra indicate that the absorbance band 875 cm−1 of the asymmetric stretching vibration of bridge oxygen P-O-P shifts to 880 cm−1, and the 1 264 cm−1 of the asymmetric stretching vibration of the bridge PO2 shifts to 1 267 cm−1 in the diaspore’s spectra. This demonstrates that sodium hexmetaphosphate interacts through bridging PO2 groups with the Al atoms exposed on the diaspore and kaolinite surfaces to form P-O-Al bond. Adsorption measurements also testify that sodium hexmetaphosphate adsorbs easily on the surface of diaspore. The adsorption density of PO3− on the surface of diaspore is about 4.7 × 10−6 mol/m2, while that on the kaolinite is only about 3.5 × 10−7 mol/m2 when pH value is 6.

Effect of hydroxamic acid polymers on reverse flotation of bauxite

The effect of hydroxamic acid starch (HAS) and hydroxamic acid polyacrylamide (HPAM) on the flotation of diaspore and kaolinite was investigated by flotation test. It is found that HAS depresses diaspore but activates kaolinite in acidic pulp, while HPAM activates both diaspore and kaolinite in the pH range of 2.0–10.5. The measurement of zeta potential shows that both HAS and HPAM can increase zeta potential of negatively charged diaspore, which indicates the existence of chemical bonding or hydrogen bonding between the reagents and diaspore. By covering the collector dodecyl amine (DDA) on diaspore surface, HAS increases the hydrophilicity of minerals and depresses the flotation of diaspore, however HPAM activates the flotation of diaspore by increasing the adsorption of DDA on diaspore surface.

Surface chemical study of the selective separation of chalcopyrite and marmatite

FCLS (Ferric Chromium Lignin Sulfonate) was used to aid the separation of chalcopyrite from marmatite. Flotation, adsorption and zeta-potential tests of treated marmatite and chalcopyrite were performed. The flotation of marmatite was strongly depressed, while that of chalcopyrite was only slightly depressed, over a wide range of pH values when FCLS was used as depressant in the presence of Butyl Xanthate (BX). The adsorption of BX onto chalcopyrite or marmatite takes place over a wide pH range. The adsorption density of BX on chalcopyrite and marmatite decreases as the pH increases. The adsorption density of FCLS onto marmatite is greater than the adsorption density onto chalcopyrite. The zeta potentials of chalcopyrite and marmatite become more negative due to the addition of xanthate and FCLS.

Fine particle aggregating and flotation behavior induced by high intensity conditioning of a CO2 saturation slurry

Abstract The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning (HIC) from saturated of the slurry with CO 2 saturation was investigated. Bubble size measurements were conducted. The effect of dissolved gas, xanthate addition and agitation speed on fine sphalerite particle aggregation- and flotation-behavior were studied. The results show that during HIC in air or CO 2 saturated water xanthate acts as a frother. The dissolved gas content in the pulp and HIC play a synergistic role in promoting fine particle aggregation and hence flotation; a significantly enhanced aggregation of fine sphalerite particles in a CO 2 saturated slurry by HIC is observed. The aggregate size increased when the agitation speed was increased from 700 r/min to 1500 r/min. Increasing the HIC speed to 1500 r/min caused a positive impact on flotation kinetics. Further increasing the speed to 2000 r/min resulted in an adverse effect on flotation kinetics.

Oxygen adsorption on pyrite (100) surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2(100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2− have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

Acidithiobacillus ferrooxidans enhanced heavy metals immobilization efficiency in acidic aqueous system through bio-mediated coprecipitation

Abstract This study investigated the promotion effect of A. ferrooxidans on complex heavy metals coprecipitation process. A. ferrooxidans significantly enhanced the ferrous oxidation, which also promoted the formation of iron-oxyhydroxysulphate. Cu(II) concentration reduced to 0.058 mmol/L in A. ferrooxidans inoculated system, and Cd also reduced to the lowest concentration (0.085 mmol/L). Pb was mainly immobilized as anglesite and iron-oxyhydroxysulphate promoted the removal of remanent Pb in solution. The precipitates are characterized by XRD, SEM, and FTIR analysis. The main component of the iron-oxyhydroxysulphate was well crystallized jarosite. A. ferrooxidans contributed to the formation of schwertmannite in later monovalent cation lack stage. Higher ferrous iron oxidation rate and Fe(III) supply rate in A. ferrooxidans inoculated system facilitated polyhedron crystal formation and the increase of particle diameter. Complex heavy metals could be incorporated into iron oxyhydroxysulphate crystal, and efficiently removed from acidic wastewater through A. ferrooxidans mediated coprecipitation.

Dynamics of electrodeposition of tetraethylthioram disulphide (TETD) on pyrite surface

The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiostatic and chronopotentiometry. Tetraethylthioram disulphide (TETD) was electrodeposited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i=1/(9.08×10−5+4.77×10−3t0.5), and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10−6 cm2/s. At pH 11.4, the thickness of TETD adsorbed on pyrite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η=0.116−0.064log[1−(t/τ)0.5]. The kinetic parameters were determined as follows: the exchange current density (i0) is 3.08 µA/cm2; the transmission coefficient(α) is 0.462.

Influence of coal sort on the direct reduction of high-iron-content red mud

The technology of coal-based direct reduction of high-iron-content red mud is studied. The factors affecting this kind of direct reduction mainly are: coal sort, carbon amount, time, temperature and etc. has been investigated. It has been shown that an ideal coal sort must have the following qualities: high reactivity, large ratio of (Fc +Vm)/A and (SiO2 +TFe)/(Al2O3 + Others) and the ability of forming a moderate porosity.