Cheon-Young Park

Characterization of Water Quality and Bacteria of Leachate from Animal Carcass Disposal on the Disposal Lapse Time

Department of Energy and Resource Engineering, Chosun University, Gwang-ju, KoreaIn this study, the physicochemical properties of leachate and the bacteria existence in leachate using molecularbiology methods for 4 animal carcass disposals on the disposal lapse time was analyzed. The result of leachatephysicochemical analysis in the middle stage (been buried 20 months) showed higher EC, DO, HCO

Attachment characteristic of indigenous acidophilic bacteria to pyrite surface in mine waste

Indigenous acidophilic bacteria living in a hot acidic spring near Hatchobaru thermal electricity plant in Japan were incubated and used for the bioleaching experiment. The indigenous acidophilic bacteria grew properly in the leaching (sulfur-rich) solution and, over the course of incubation, the pH decreased and Eh increased. In relation to the bacterial growth-curve, the lag phase was hardly shown while the exponential phase was significantly fast. Following Gram staining of the bacteria, they were categorized into Gram-negative and Gram-positive. When the bacteria were inoculated to pyrite, rod-shaped bacteria and round-shaped microbes were well attached to the surface of the pyrite. The size of the rod-shaped bacteria ranged from 1.05–1.10 μm to 4.01–5.38 μm. Round-shaped microbes were more than 3.0 μm in diameter. Paired cells of rod-shaped bacteria were linearly attached to the surface of the pyrite. The round-shaped microbes showed strong organic attachment. Twenty days after the indigenous acidophilic bacteria were inoculated to a pyrite-leaching medium, the bacterial sample had a greater concentration of Fe and Zn than within the control sample.

Enhancement of gold recovery during lead fire assay by salt-roasting

The aim of this study was to investigate the effect of a simple and economical salt-roasting method on the gold recovery of a conventional lead fire assay. An enhanced gold recovery of 30.99 g/ton (16.82%) was obtained by roasting a gold concentrate at 750°C, but this was further enhanced to 40.44 g/ton (21.95%) at the same temperature with the addition of 20% salt. The fact that the maximum recovery was obtained at a roasting temperature of 750°C was attributed to the fact that pyrites within the concentrate contained invisible gold, with the addition of salt enhancing the decomposition of these pyrites. Thus, by treating the gold concentrate with a combination of conventional and salt roasting, its gold content was increased and the loss of gold to the glass slag was reduced. Finally, it was also observed that the amount of gold loss with an amorphous specimen was less than that of samples containing galena.

The Characteristic of Te Recovery in Gold Concentrate Using Electrolysis

Department of Rural Systems Engineering/Research Institute for Agriculture and Life Science, Seoul NationalUniversity, Seoul, Korea In order to obtain pure metallic Te from gold concentrate, roasting treatment, hypochlorite leaching, Fe removaland electrolysis experiments were carried out. The contents of Au, Ag and Te from the concentrate sample androasted sample were much more soluble in the hypochlorite solution than in aqua regia digestion, whereas the met-als Pb, Zn, Fe and Cu were easier to leach with the aqua regia than the hypochlorite. With the addition of NaOHin the hypochlorite leaching solution prior to electrolysis, the Fe removal rate achieved was only 96% in the con-centrate sample, while it reached 98% in the roasted sample. The results of electrolysis for 240 min, 98% of themetallic copper was recovered from the concentrate sample, while 99% was obtained from the roasted sample dueto the removal of S by roasting. The amount of anode slime was also greater in the electrolytic solution with theroasted sample than with the concentrate sample. The results on the anode slime after the magnetic separation pro-cess showed the amount of metallic pure native tellurium recovered was greater in the roasted sample than in theconcentrate sample.

The Efficiency of Bioleaching Rates for Valuable Metal Ions from the Mine Waste Ore using the Adapted Indigenous Acidophilic Bacteria with Cu Ion

This study was carried out to leach valuable metal ions from the mine waste ore using the adapted indigenous bacteria. In order to tolerance the heavy metals, the indigenous bacteria were repeatedly subcultured in the adaptation-medium containing for 3 weeks and 6 weeks, respectively. As the adaptation experiment processed, the pH was rapidly decrease in the adaptation-medium of 6 weeks more than the 3 weeks. The result of bioleaching with the adapted bacteria for 42 days, the pH value of leaching-medium in the 3 weeks tend to increased, whereas the pH of the 6 weeks decreased. In decreasing the pH value in the adaptation-medium and in the leaching-medium, it was identified that the indigenous bacteria were adapted the ion and the mine waste ores. The contents of Cu, Fe and Zn in the leaching solution were usually higher leached in 6 weeks than 3 weeks due to the adaptation. Considering the bioleaching rates of Cu, Fe and Zn from these leaching solutions, the highest increasing the efficiency metal ion were found to be Fe. Accordingly, it is expected that the more valuable element ions can be leached out from the any mine waste, if the adapted bacteria with heavy metals will apply in future bioleaching experiments.

Bioleaching of chalcopyrite using indigenous acidophilic bacteria under moderate thermopile conditions

This study focused on the successful growth of the indigenous acidophilic bacteria living in Japanese acid hot springs in a growth medium containing elemental sulfur under moderate thermopile conditions. As the bacteria grew in the growth medium, its pH decreased and Eh increased. While the rod-shaped bacteria of about 1 μm grew into many populations at the medium length of 5 μm, a strain of above 9.8 μm grew only in a small minority. When the bacteria were stained with Gram, some bacteria 1 μm in length were proved Gram negative, and larger bacteria which were 5-6 times longer than those of 1 μm were proved Gram positive. The colonies of rod-shaped bacteria 1 μm in morphology and 1 μm in length were attached to the chalcopyrite surface and those with filament morphology ranging from 6 μm to 8.5 μm in length were attached singularly. When the indigenous acidophilic bacteria were inoculated on a chalcopyrite surface, the ion concentrations in Cu, Fe and Zn leached were two, four and six times higher than those of the controlled sample, respectively. In particular, as the indigenous acidophilic bacteria were inoculated with the chalcopyrite-leaching medium and the pH was not adjusted using sulfuric acid, the capacity of bioleaching could be compared with the capacity of inorganic leaching. The ion concentrations in Cu and Fe were very high in the sample with bacteria due to their excellent leaching capacity. However, the behavior of the leaching curve of the Zn and As in concentrations showed similarity to both the sample with and that without bacteria.

Comparative analysis for fouling characteristics of river water, secondary effluent, and humic acid solution in ceramic membrane ultrafiltration

ABSTRACT Ceramic membrane ultrafiltration experiments were performed with 7-channel tubular membrane (molecular weight cutoff = 300 kD) at a constant transmembrane pressure and crossflow rate under recirculation mode. In the experiments, the fouling characteristics of river water (RW, dissolved organic carbon (DOC) = 3.4 mg/L) were compared with humic acid solution (HA1, DOC = 3.7 mg/L). Also, the fouling behaviors of secondary effluent (SE, DOC = 7.9 mg/L) were compared with HA2 (DOC = 8.5 mg/L). Fluorescence excitation-emission matrix, modified Hermia’s model, and resistance-in-series model were used to analyze the fouling characteristics. Results demonstrated that RW and SE could cause ceramic membrane fouling more rapidly due to their hydrophilic organic compositions in comparison with hydrophobic HA.

Enhancement of Discfilter Removal Efficiency for Small-scale Wastewater Reclamation

ABSTRACT The aim of this study was to enhance of the Discfilter process (maximum treatment capacity - 500 ton/day) removalefficiency for small-scale wastewater reclamation under various influent wastewater conditions (with / without coagulationprocess, coagulant content and temperature). The result of chemical resistance test for fiber filter in the Discfilter thatweight loss was obtained with 0.535% under pH 3, 0.092% under pH 9 and 0.028% under 10% NaClO. The removalefficiency test of Discfilter process on the with / without coagulation process showed that with coagulation processcondition was occurred COD Mn of 42.26±0.61, BOD 5 of 88.72±0.44, T-P of 84.67±0.72 and SS of 90.58±0.61. Theremoval efficiency of Discfilter process on the coagulant content (4.5, 5.0 and 5.0 mL/min) and temperature ( 20 o C) conditions were increased as coagulant content and temperature increased. This study demonstratedthe potential application of Discfilter process for small-scale wastewater reclamation.Key words : Wastewater reclamation, Discfilter, Coagulation, Temperature, Removal

The Leaching and Recovery of Au from Scrap of PCBs

This study was carried out to find an environmental friendly and effective way to leach Au and Ag from scrap of Printed Circuit Boards (PCBs) using sodium-hypochlorite solution. In an EDS analysis, valuable metals such as Cu, Sn, Sb, Al, Ni, Pb and Au were all found in PCBs. The highest leaching rates obtained were 1% of pulp density with a chlorine:hypochlorite of 2:1 and a concentration of NaCl at 2M. The highest Au recovery was observed with the addition of sodium metabisulfite to make a 3M solution. It is confirmed that the leaching agent (chlorine-hypochlorite) could effectively leach Au and Ag from Printed Circuit Boards (scrap parts) and the additive reagent sodium metabisulfite could easily precipitate Au from the chlorine-hypochlorite solution.

Optimization of Gold Leaching from the Refractory Sulfide Concentrate by HCl-NaClO-FeCl 3 Solution

In order to optimize gold leaching from refractory sulfide concentrate, a HCl-NaClO-FeCl3 solution with varying attributes was applied to the roasted concentrate from Uil mine. The gold from Uil mine occurs in the form of invisible gold that is difficult to leach. The results of the gold leaching experiments showed that the best gold leaching parameters were 550 o C of roasting temperature, 2.0 M of concentration, 1.0% of pulp density, and 70 o C of leaching temperature. It is confirmed that the HCl-NaClO-FeCl3 solution was an environmentally friendly method to leach gold and silver from the refractory sulfide concentrate as an alternative lixiviant to cyanide.