Sookyun Wang

Heavy metal removal in groundwater originating from acid mine drainage using dead Bacillus drentensis sp. immobilized in polysulfone polymer.

Batch, column, and pilot scale feasibility experiments for a bio-sorption process using a bio-carrier (beads) with dead Bacillus drentensis sp. in polysulfone polymer were performed to remove heavy metals in groundwater originating from an acid mine drainage (AMD). For batch experiments, various amounts of bio-carrier each containing a different amount of dead biomass were added in artificial solution, of which the initial heavy metal concentration and pH were about 10 mg/L and 3, respectively. The heavy metal removal efficiencies of the bio-carrier under various conditions were calculated and more than 92% of initial Pb and Cu were found to have been removed from the solution when using 2 g of bio-carriers containing 5% biomass. For a continuous experiment with a column packed with bio-carriers (1 m in length and 0.02 m in diameter), more than 98% of Pb removal efficiency was maintained for 36 pore volumes and 1.553 g of Pb per g of bio-carrier was removed. For the pilot scale feasibility test, a total of 80 tons of groundwater (lower than pH of 4) were successfully treated for 40 working days and the removal efficiencies of Cu, Cd, Zn, and Fe were maintained above 93%, demonstrating that one kg of bio-carrier can clean up at least 1098 L of groundwater in the field.

Study on the Dissolution of Sandstones in Gyeongsang Basin and the Calculation of Their Dissolution Coefficients under CO 2 Injection Condition

Lab scale experiments to investigate the dissolution reaction among supercritical -sandstone-groundwater by using sandstones from Gyeongsang basin were performed. High pressurized cell system (100 bar and ) was designed to create supercritical in the cell, simulating the sub-surface storage site. The first-order dissolution coefficient () of the sandstone was calculated by measuring the change of the weight of thin section or the concentration of ions dissolved in groundwater at the reaction time intervals. For 30 days of the supercritical -sandstone-groundwater reaction, physical properties of sandstone cores in Gyeongsang basin were measured to investigate the effect of supercritical on the sandstone. The weight change of sandstone cores was also measured to calculate the dissolution coefficient and the dissolution time of 1 g per unit area (1 ) of each sandstone was quantitatively predicted. For the experiment using thin sections, mass of and dissolved in groundwater increased, suggesting that plagioclase and calcite of the sandstone would be significantly dissolved when it contacts with supercritical and groundwater at sequestration sites. 0.66% of the original thin sec-tion mass for the sandstone were dissolved after 30 days reaction. The average porosity for C sandstones was 8.183% and it increased to 8.789% after 30 days of the reaction. The average dry density, seismic velocity, and 1-D compression strength of sandstones decreased and these results were dependent on the porosity increase by the dissolution during the reaction. By using the first-order dissolution coefficient, the average time to dissolve 1 g of B and C sandstones per unit area (1 ) was calculated as 1,532 years and 329 years, respectively. From results, it was investigated that the physical property change of sandstones at Gyeongsang basin would rapidly occur when the supercritical was injected into sequestration sites.

Physical property changes of sandstones in Korea derived from the supercritical CO2-sandstone‒groundwater geochemical reaction under CO2 sequestration condition

Laboratory experiments and calculation of the dissolution constant were performed to investigate the physical property changes of sandstones in Korea resulting from the geochemical reaction of CO2 under sequestration conditions. To simulate the sub-surface storage condition (100 bar and 50 °C), the high pressurized stainless cell and chamber were used and the supercritical CO2 fluid was injected into the cell (or the chamber) by the syringe pump and the pressure regulator. Sandstone slabs and cores were used for the experiments of the supercritical CO2-sandstone‒groundwater reaction. Results of SEM/EDS and SPM analyses showed that the surface roughness of the slab increased and the precipitation of calcite, halite, and Ca-rich silicate minerals on the sandstone slab occurred during 60 days reaction, suggesting the geochemical weathering process, as a result of CO2 injection, directly leads to property changes of sandstones in a short time. The average porosity of sandstone cores as increased 8.8% with the corresponding decreases in the dry density, P and S wave velocity, dynamic Young’s modulus, and the uniaxial compression strength, indicating that the trend of property changes for the sandstone was well fitted to the first-order reaction curve. The average first-order dissolution constant (K1) of sandstones, calculated by using the loss of sandstone mass during the reaction time was 0.0000846 day−1. The K1 values will be useful for estimating the dissolution process of sandstones originated from the supercritical CO2-sandstone‒groundwater reaction while the CO2 was injected into the sub-surface.

Study on the Geochemical Weathering Process of Sandstones and Mudstones in Pohang Basin at CO 2 Storage Condition

Laboratory experiments for the reaction with supercritical under the sequestration condition were performed to investigate the mineralogical and geochemical weathering process of the sandstones and mudstones in the Pohang basin. To simulate the supercritical -rock-groundwater reaction, rock samples used in the experiment were pulverized and the high pressurized cell (200 ml of capacity) was filled with 100 ml of groundwater and 30 g of powdered rock samples. The void space of the high pressurized cell was saturated with the supercritical and maintained at 100 bar and for 60 days. The changes of mineralogical and geochemical properties of rocks were measured by using XRD (X-Ray Diffractometer) and BET (Brunauer-Emmett-Teller). Concentrations of dissolved cations in groundwater were also measured for 60 days of the supercritical -rock-groundwater reaction. Results of XRD analyses indicated that the proportion of plagioclase and K-feldspar in the sandstone decreased and the proportion of illite, pyrite and smectite increased during the reaction. In the case of mudstone, the proportion of illite and kaolinite and cabonate-fluorapatite increased during the reaction. Concentration of and dissolved in groundwater increased during the reaction, suggesting that calcite and feldspars of the sandstone and mudstone would be significantly dissolved when it contacts with supercritical and groundwater at sequestration sites in Pohang basin. The average specific surface area of sandstone and mudstone using BET analysis increased from and to and , respectively, and the average size of micro scale void spaces for the sandstone and mudstone decreased over 60 days reaction, resulting in the increase of micro pore spaces of rocks by the dissolution. Results suggested that the injection of supercritical in Pohang basin would affect the physical property change of rocks and also storage capacity in Pohang basin.

Development and Application of Micromodel for Visualization of Supercritical CO 2 Migration in Pore-scale

Despite significant effects on macroscopic migration and distribution of CO2 injected during geological sequestration, only limited information is available on wettability in microscopic scCO2-brine-mineral systems due to difficulties in pore-scale observation. In this study, a micromodel had been developed to improve our understanding of how scCO2 flooding and residual characteristics of porewater are affected by the wettability in scCO2-water-glass bead systems. The micromodel (a transparent pore structure made of glass beads and glass plates) in a pressurized chamber provided the opportunity to visualize scCO2 spreading and porewater displacement. CO2 flooding followed by fingering migration and dewatering followed by formation of residual water were observed through an imaging system. Measurement of contact angles of residual porewater in micromodels were conducted to estimate wettability in a scCO2-water-glass bead system. The measurement revealed that the brine-3M NaCl solution-is a wetting fluid and the surface of glass beads is water-wet. It is also found that the contact angle at equilibrium decreases as the pressure decreases, whereas it increases as the salinity increases. Such changes in wettability may significantly affect the patterns of scCO2 migration and porewater residence during the process of CO2 injection into a saline aquifer at high pressures.

Pore-scale Investigation on Displacement of Porewater by Supercritical CO 2 Injection Using a Micromodel

A micromodel was applied to estimate the effects of geological conditions and injection methods on displacement of resident porewater by injecting scCO2 in the pore scale. Binary images from image analysis were used to distinguish scCO2filled-pores from other pore structure. CO2 flooding followed by porewater displacement, fingering migration, preferential flow and bypassing were observed during scCO2 injection experiments. Effects of pressure, temperature, salinity, flow rate, and injection methods on storage efficiency in micromodels were represented and examined in terms of areal displacement efficiency. The measurements revealed that the areal displacement efficiency at equilibrium decreases as the salinity increases, whereas it increases as the pressure and temperature increases. It may result from that the overburden pressure and porewater salinity can affect the CO2 solubility in water and the hydrophilicity of silica surfaces, while the neighboring temperature has a significant effect on viscosity of scCO2. Increased flow rate could create more preferential flow paths and decrease the areal displacement efficiency. Compared to the continuous injection of scCO2, the pulse-type injection reduced the probability for occurrence of fingering, subsequently preferential flow paths, and recorded higher areal displacement efficiency. More detailed explanation may need further studies based on closer experimental observations.

Characterization of Selenium (Se) Distribution in Soils and Crops at Moi-san, Haenam

Department of Energy Resources Engineering, Pukyong National University(Received: 23 June 2015 / Accepted: 29 June 2015)Samples from soils and crops were collected and analyzed in order to investigate the interactions of seleniumamong rocks, soils, and crops by hydrothermal alteration near epithermal mines in the region of Mio-san, Haenam.Soil samples included 6 samples each from mountain and farm area and compositional minerals and their contentswere analyzed by water content, pH, ICP, XRD, XRF. Crop samples from onion and scallion were analyzed forchemical composition to elucidate the relationship with soils. Results from XRD analysis for soil samples showedthat major compositional minerals are qualtz and feldspar, and illite, chlorite, hematite formed by hydrothermalalteration were included on a small scale. The pH ranges of soil samples from mountain and farm were measuredat 4.6~4.9 and 5.2~6.7, respectively. The higher pH in farm soils may result from fertilization during agriculturalactivities. Results from ICP analysis showed that, compared to soil samples from mountain area with no potassiumand calcium, significant amount of K and Ca were detected in soil samples from farms which is affected by fertili-zation. In a similar manner, potassium and calcium were absorbed and detected in crop samples at relatively highconcentrations (116.89~169.79 ppm for K and 20.18~32.29 ppm for Ca). While the selenium contents in soil sam-ples ranged from 18.35 ppb to 70.31 ppb which showed no significant difference, high concentrations of seleniumwere detected in onion (119.48~179.50 ppb) and scallion (146.65 ppb). These difference in enrichment for each ele-ment may result from the distinctive adsorption characteristics depending on crops.

A Mineralogical and Gemological Studies for the Enhancement of Tanzania Ruby by Heat Treatment

Department of Earth Environmental Science, Pukyong National UniversityRuby is one of the most favor colored gem, for beautiful red tone, be high in scarcity value. However, rubieswith high quality are produced in restricted regions, such as in Thailand, Sri Lanka, Myanmar, and Tanzania etc.,and they have been gradually exhausted by mining for a long period. Therefore, improving qualities of low levelrubies with various treatments is arising an alternative way to obtain better rubies. Gemological and mineralogicalproperties of the natural ruby from Tanzanian were studied with heat treatments. Those characteristics were com-pared between only heat and adding flux materials under heating. Tanzanian raw rubies were applied a heat treat-ment (1,600°C for 6 hours). However, chromameter and UV-Vis analyses found that a simple heat treatment isinappropriated for the Tanzanian ruby. Although Cr