It is well known that galvanic interaction between sulfide minerals and manganese oxides in manganese nodules accelerates the leaching of sulfide minerals. Zinc-carbon batteries contain a moist paste (hereafter, black paste) of manganese oxides and graphite powder as cathode mix. We have investigated the feasibility of galvanic leaching of chalcopyrite using chemical reagent MnO2 and black paste. Addition of MnO2 enhanced the leaching of chalcopyrite in sulfuric acid media with pH 1.0 and Mn concentration also increased remarkably. Extraction yields of Cu and Mn were 52% and 23% respectively at a MnO2 to chalcopyrite mass ratio of 4 in 24 days. In the presence of black paste the kinetics of chalcopyrite leaching was accelerated dramatically and 83% of Cu in the concentrate was extracted in 40 hours. The graphite powder contained in black paste could play an important role in the galvanic leaching of chalcopyrite in the presence of MnO2.
The properties of Bordetella petrii strain KC42 isolated from the soil in Miyazaki Prefecture were investigated in terms of arsenic methylation and removal in this study. No differences were observed in the growth of strain KC42 between As(III)- and As(V)-supplemented culture medium. Strain KC42 metabolized inorganic arsenic (<5.0 mgAs/L) to nonvolatile species such as monomethylarsonic acid, dimethylarsinic acid, trimethylarsenic oxide and arsenobetaine effectively. In culture supplemented with 0.2 mg As/L As(V), 98.7% of the arsenic remaining in the supernatant was found to be methylated organic arsenic compounds. An analysis of the arsenic adsorbed to the bacterial cell walls revealed that most of the arsenic removed from culture medium was accounted by cell wall adsorption for both As(III)- and As(V)-supplementation, and that in both cases, all of the adsorbed arsenic was in the As(III) form. These results demonstrate that strain KC42 possesses arsenic-methylating and arsenic-removing capabilities, and may therefore be used in the bioremediation of arsenic.
Bordetella petrii strain KC42 isolated from soil in Miyazaki prefecture was shown to be a microorganism with methylation and removal activities of inorganic arsenic. Arsenic methylation using intracellular extracts from strain KC42 at pH 6.5 and 35°C for 2 h yielded 35.9% methylated organic arsenic compound and 10.8% trimethylarsenic compound (TMAC). As a result of the analysis of TMAC produced under these conditions, TMAC was identified by trimethylarsine oxide and arsenobetaine. In experiments of arsenic adsorption by dried cells of strain KC42, the ratio of As(III) adsorption by strain KC42 was 99.4% in solutions containing 0.2 mg As/L at pH 7.0 and 30°C for 2 h. The maximum adsorption value was 0.179 mg As/g dw at an initial concentration of 10.0 mg As/L As(III). These results suggest that strain KC42 may be utilized for bioremediation
The separation of nickel(II) and cobalt(III) from ammoniacal solutions with ACORGA M5640 (5-nonylsalicylaldoxime) as an extractant was investigated. The extraction of cobalt(III) decreased significantly due to the formation of Co(NH3)63+ above pH 4. Meanwhile, the extraction of nickel(II) increased above pH 4. The separation efficiency of both metals is sufficiently improved due to the oxidation of cobalt(II) to cobalt(III) in the ammoniacal solutoions and nickel(II) could be extracted preferentially from cobalt(III) with ACORGA M5640.