Nie Zhenyuan

Effect of sodium chloride on sulfur speciation of chalcopyrite bioleached by the extreme thermophile Acidianus manzaensis.

The influence of sodium chloride on dissolution of chalcopyrite and surface sulfur speciation during bioleaching of chalcopyrite with the extreme thermophile Acidianus manzaensis YN-25 was studied. The addition of sodium chloride accelerated the dissolution of chalcopyrite by reducing the accumulation of elemental sulfur layers on the mineral surface, resulting in an increase in the concentration of copper ions from 2.37g/L to 2.67g/L. Jarosite and elemental sulfur were found in the bioleached residues, while the amount of elemental sulfur accumulating on the mineral surface decreased drastically from 25.4% to 3.0% when 0.66g/L of sodium chloride was present during bioleaching. Therefore, the accumulation of elemental sulfur on the mineral surface is likely mainly responsible for the slowdown in the dissolution rate. The results indicated that bioleaching chalcopyrite with extreme thermophiles possessing high sulfur oxidation activity likely enhances dissolution of chalcopyrite by effectively removing elemental sulfur accumulating on the mineral surface.

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.

Structure, properties and application to water-soluble coatings of complex antimicrobial agent Ag-carboxymethyl chitosan-thiabendazole

The structure, properties and application to water-soluble coatings of a new complex antimicrobial agent Ag-carboxylmethyl citosan-thiabendazole (Ag-CMCTS-TBZ) prepared from different materiel ratios were reported. The silver ions were preferably coordinated with the free — NH2 groups and the — OH groups of secondary alcohol and carboxyl in CMCTS. TBZ preferably bonded to carboxyl group in CMCTS by electrostatic force and hydrogen bonding. Increase in silver ions content in the complex agent improved to some limited extent the antibacterial activity, but enhanced coloring and cost of the complex agent. Increase in TBZ content resulted in increase of antifungal activity, but decrease of water solubility of the complex agent. The antimicrobial MICs of the complex agent to Esherichia coli, Staphylococcus aureus, Candida albicans, Aspergillus niger, Mucor sp. were 20 – 80, 15 – 60, 20 – 55, 40 – 250, and 400 – 1700 mg/kg, respectively. Addition of 0.1% of this complex agent to acrylic emulsion paint made the paint without substantial change in color, luster, viscosity, odor or pH value, but with an excellent and chronically persisting broad-spectra antimicrobial activity.

Preparation, optical properties and cell staining of water soluble amine-terminated PAMAM G2.0-Au nanocomposites

The solution chemical and optical characteristics of formation of amine-terminated polyamidoamine dendrimer G2.0(NH2-PAMAM G2.0)-Au nanocomposites in the aqueous solution of NH2-PAMAM G2.0 at various mole ratios of Au(III) to NH2-PAMAM G2.0 were studied by both UV-visible spectrometry and fluorospectrometry. The NH2-PAMAM G2.0-Au nanocomposites, with a type of structure in which one Au nanoparticle is surrounded by several NH2-PAMAM G2.0 dendrimers, emit strong bluish violet fluorescence, and are uniform, water soluble and biocompatible as well as very stable in frozen conditions. The size of gold nanoparticles in the nanocomposites is about 2.5 nm and decreases with the increase of NH2-PAMAM G2.0 concentration. The NH2-PAMAM G2. 0 plays an important role in acting as host or micro-reactor for Au(III) before Au(III) reduction and acting as dispersant and stabilizer for gold nanoparticles after Au(III) reduction. Preliminary experiments of cells staining to human embryonic lung fibroblast cell lines show that the NH2-PAMAM G2.0-Au nanocomposites can be used as optical imaging markers for bioanalyses and medical diagnoses.