Qiu Guan-zhou

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.

Biosorption mechanism of Cr (VI) onto cells of Synechococcus sp.

The biosorption mechanism of Cr (VI) ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr (VI) consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-IR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp. show that the speciation of chromium that binds to the cells of Synechococcus sp. is Cr (III), instead of Cr (VI), and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr (III). Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr (VI), and the results of FT-IR show that the biosorption of Cr (VI) follows two subsequent steps, biosorption of Cr2O72− by electrostatical force at the protonated active sites and reduction of Cr2O72− to Cr3+ by the reductive groups on the surface of the biosorbents.

Isolation and characterization of Acidithiobacillus caldus from several typical environments in China

Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45–50 °C and 2.5–3.5 respectively. They are autotrophic and used elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.

Bioleaching of chalcopyrite by mixed culture of moderately thermophilic microorganisms

A mixed culture of moderately thermophilie microorganisms was enriched from acid mine drainages(AMDs) samples collected from several sulphide mines in China, and the bioleaching of chalcopyrite was conducted both in shake flask and bioreactor. The results show that in the shake flask, the mixture can tolerate 50 g/L chalcopyrite after being acclimated to gradually increased concentrations of chalcopyrite. The copper extraction increases obviously in bioleaching of chalcopyrite with moderately thermophilic microorganisms supplemented with 0.4 g/L yeast extract at 180 r/min, 74% copper can be extracted in the pulp of 50 g/L chalcopyrite after 20 d. Compared with copper extractions of mesophilic culture, unacclimated culture and acclimated culture without addition of yeast extract, that of accliniated culture with addition of yeast extract is increased by 53%, 44% and 16%, respectively. In a completely stirred tank reactor, the mass fraction of copper and total iron extraction reach up to 81% and 56%, respectively. The results also indicate that it is necessary to add a large amount of acid to the pulp to extract copper from chalcopyrite effectively.

ONE-STEP LEACHING OF SOME REFRACTORY GOLD CONCENTRATE CONTAINING ARSENIC AND THEORY ANALYSIS*

A new technology of one-step leaching of refractory gold concentrate containing arsenic and sulfur was studied and 96.8% of gold was extracted in an hour by this technology. Themodynamic possibility of reactions of arsenopyrite, pyrite and gold with sodium hypochlorite in NaOH medium, and solution chemistry of H3AuO3 at different pH values were analyzed. The reason why the gold wrapped by FeAsS, FeS2 can be leached out rapidly by grnding of porcelain ball mill, is explained.

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.

Comparison of microbial communities in three different mine drainages and their bioleaching efficiencies to low grade of chalcopyrite

Microbial community diversities in the drainage from three mines (Dexing Copper Mine, Qibaoshan Copper Mine and Yaogangxian Tungsten Mine, China) were analyzed using 16S rDNA PCR-RFLP approach. The efficiencies of clalcopyrite bioleaching were compared using enrichment of the three cultures. Phylogenetic analysis indicates that the dominant microorganisms are clustered with the Proteobacteria, the remaining is affiliated with Nitrospira, Acidobacteria and Actinobacteria. At the genus level, Acidithiobacillus is the dominant group in both YTW and QBS samples, while Spingomonas is dominant in YGX sample. Moreover, the principal component analysis (PCA) reveals that QBS and YTW have similar geochemical character and microbial communities. The results also show that pH value and tungsten concentration play a key role in microbial community distribution and relative abundance. The bioleaching efficiency of the enrichment cultures from YTW and QBS is similar. After 15 d, the bioleaching rates of low grade chalcopyrite (0.99%) are both up to 99.5% when using 10 g/L pulp density due to the similar microbial composition of YTW and QBS. Moreover, the leaching efficiencies of enrichment cultures containing multiple bioleaching microorganisms are higher than that of pure culture Acidithiobacillus ferrooxidans.

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.

Cement industry control system based on multi agent

Cement production is characterized by its great capacity, long-time delay, multi variables, difficult measurement and multi disturbances. According to the distributed intelligent control strategy based on the multi agent, the multi agent control system of cement production is built, which includes integrated optimal control and diagnosis control. The distributed and multiple level structure of multi agent system for the cement control is studied. The optimal agent is in the distributed state, which aims at the partial process of the cement production, and forms the optimal layer. The diagnosis agent located on the diagnosis layer is the diagnosis unit which aims at the whole process of the cement production, and the central management unit of the system. The system cooperation is realized by the communication among optimal agents and diagnosis agent. The architecture of the optimal agent and the diagnosis agent are designed. The detailed functions of the optimal agent and the diagnosis agent are analyzed. At last the realization methods of the agents are given, and the application of the multi agent control system is presented. The multi agent system has been successfully applied to the off-line control of one cement plant with capacity of 5 000 t/d. The results show that the average yield of the clinker increases 9.3% and the coal consumption decreases 7.5 kg/t.