Jun-Heok Lim

Biosorption Characteristics in the Mixed Heavy Metal Solution by Biosorbents of Marine Brown Algae

The biomass of nonliving, dried marine brown algaeU. pinnatifida, H. fusiformis, andS. fulvellum harvested in the sea near Cheju Island, Korea were studied for their sorption ability of copper, zinc, and lead. The metal uptakes by biosorbent materials increased with increasing initial metal concentration and pH in the range of Ci 0.0510 mM. The higher metal uptakes were obtained in the range of pHs 4.0–5.3, 4.0–6.0, and 3.0–6.0 for copper, lead, and zinc, respectively. The metal uptakes by biosorbent materials decreased in the following sequence:U. pinnatifida> H. fusiformis> S. fulvellum. The maximum metal uptake values ofU. pinnatifida for Cu2+, Pb2+, and Zn2+ in the single metal solution are 2.58, 2.6, and 2.08 meq/g in the range of pHs 5.3–4.4, respectively. The metal uptakes by biosorbent materials in the mixed metal solution decreased greatly in comparison to each metal uptake in the single metal solution.

Reduction of carbon dioxide in 3-dimensional gas diffusion electrodes

Experiments on the electrochemical reduction of CO2 were carried out by using a Cu/PTFE-bonded gas diffusion electrode (GDE) to investigate the effect of solvents, Cu/C ratio and electrolyte concentration on the characteristics of reduction products The experimental conditions were a voltage range from -2 0 to -3 5 V vs saturated calomel electrode (SCE) and electrolyte concentration from 0 1 M to 0 5 M Significant performance differences were found between water and organic solvent (isobutanol + EtOH) The GDE was more active with water than that with organic solvent And then, in the case of the Cu/PTFE-bonded gas diffusion electrode using organic solvent, the maximum faradaic efficiencies of reduction products were achieved in a Cu/C ratio of 0 5 The faradaic efficiency of C2H4 among the reduction products decreased as the Cu/C ratio increased, whereas, those of CO and alcohol increased Since the difference in pH at the electrode influences the variation of product selectivity, the faradaic efficiency of C2H4 might increase due to the pH increase caused by electrolyte concentration difference

An optimal design approach of gas hydrate and reverse osmosis hybrid system for seawater desalination

AbstractGas hydrate (GH) desalination process is based on a liquid (salty water) to solid (GH) phase change coupled with a physical process to separate the GHs from the remaining salty water. However, GH process exhibits less than 90% of salt rejection, so reverse osmosis (RO) process is needed to finally meet the desalinated product water quality. In order to increase the total recovery of the GH and RO hybrid system, the concentrate of the RO process should return to the feed stream of the GH process. In this work, RO simulation was carried out to find an optimal RO recovery with which the energy consumption of RO was minimized. The optimal RO recovery values for GH processes with salt rejection of 78, 84, and 90% were 0.6, 0.8, and 0.8, respectively. The minimal total energy consumption appears at higher RO recovery rates than the optimal values to minimize the RO energy consumption because the portion of the GH energy consumption is inversely proportional to the RO recovery. The simulation also reveal...

A simulation of electrochemical kinetics for gas-liquid-solid phase of MCFC anode

A porous Ni-Al alloy anode for the molten carbonate fuel cell has been developed to enhance the creep resistance of the anode as well as to minimize the electrolyte loss A dual-porosity filmed agglomerate model for the Ni-Al alloy anode has been investigated to predict the cell performance The major physicochemical phenomena being modeled include mass transfer ohmic losses and reaction kinetics at the electrode-electrolyte interface The predicted polarization curves are compared with the experimental results obtained from a half cell test The model predicted very well the steady-state cell performance at the given conditions that characterize the state of the electrode

Enhanced boron removal using polyol compounds in seawater reverse osmosis processes

AbstractThe removal of boron is a very important issue in desalination using seawater reverse osmosis (SWRO). A novel approach using polyol compounds to remove boron is introduced in this study. Polyols are compounds possessing multiple hydroxyl groups and they can combine with uncharged boric acid by generating anionic complexes. As a result, a large molecule is formed and it can be easily rejected by SWRO membrane at seawater pH. Lab-scale SWRO tests were performed to investigate the effect of polyol on the boron removal using different types of polyol (xylitol, glycerol, and D-mannitol). The polyol–boron reaction occurs in seawater condition with low boron concentration and various ion compounds, which leads to two important findings that boron-polyol reaction occurs with low boron and polyol concentrations, and there are no significant inhibitors for the reaction in seawater. The boron-polyol reaction rate is so fast that it can be easily applied to full-scale SWRO processes. The boron removal rate in...

Optimum conditions for cultivation of Chlorella sp. FC-21 using light emitting diodes

The purpose of this study was to determine the optimum conditions for the cultivation of Chlorella sp. FC-21 under light-emitting diodes (LEDs). Specific growth rates and Chlorella cell concentrations were measured when they were grown under different LED wavelengths (red, blue, white, and mixed). The red LEDs were the most effective light source as determined by increases in specific growth rates and cell concentrations. Cell concentrations increased as light intensity was increased; however, the specific growth rate decreased as the initial cell concentration rose due to the shading effect of cells in the reactor. To determine if aeration is beneficial during cell cultivation, micro-air bubbles were aerated at 0.70 vvm in the reactor under red LED illumination. Aeration led to two- and ten-times greater specific growth rates. Our findings show that red LEDs with aeration are optimal for cultivation of Chlorella sp. FC-21.

Effects of various reaction conditions on the hydrothermal treatment of polypeptone

This study investigated the production behavior of amino acids from polypeptone under various operation parameters and reactor modes (batch and continuous). In the batch experiments, the effect of heating time on amino acid production was studied using different type of reactor materials (Hastelloy (HAS) and SUS). The results showed that the production behavior of amino acids such as Gly, Ala, and Leu was quite similar regardless of reactor materials. To further investigate the relationship of reaction time on the amino acids production, experiments were conducted in batch and continuous reaction at the same conditions (T=523 K and P=30 MPa). The results showed that it is possible to get the same result at the same reaction time using a batch and continuous reaction mode if the reaction time is started after heating time in a batch reaction mode. From the study of reaction pressure, it was observed that the production of amino acids is not favored at reaction pressure between 4 and 30 MPa at 523 K.

CO2 absorption characteristics of a jet loop reactor with a two-fluid swirl nozzle in an alkaline solution

To investigate the performance of a jet loop reactor with the two-fluid swirl nozzle (TSN), CO2 absorption experiments in an alkaline solution were performed. The experimental results obtained in the reactor were compared with those in a jet loop reactor with the two-fluid conventional nozzle (TCN). The neutralization time of alkaline solution and the CO2 removal efficiency were used as the indices for a comparison of the reactor performance. Due to the swirling flow, the neutralization times of alkaline solutions by CO2 in the reactor with the TSN were shortened compared with those in the reactor with the TCN. Also, the instantaneous and/or overall CO2 removal efficiencies in the reactor with the TSN were higher than those in the reactor with the TCN at the same liquid circulation flow rate.

Cultivation of Chlorella Sp. Using Light Emitting Diode

The purpose of this study was to determine optimum conditions for the cultivation of Chlorella sp. FC-21 using light emitting diodes (LEDs). Specific growth rate and cell concentration were measured for the reactors at the illuminations of different wavelengths of LEDs. Among various types of LEDs, red LEDs were the most effective light source, and also greatest increases of specific growth rate and cell concentrations were obtained when light intensity of red LEDs increased. The specific growth rate decreased when initial cell concentration increased due to the shading effect of each cell in the reactor. To determine beneficial effect of aeration to cell cultivation, micro-air bubbles were aerated at 0.35 vvm in the reactor at the illumination of red LEDs. Two and ten times greater specific growth rate and cell concentration were obtained when aeration was applied. From this study, we found that red LEDs with aeration were the most appropriate light source for the cultivation of Chlorella sp. FC-21.

Photochemical heterogeneous catalytic reaction at recirculated reactor system

A study was undertaken to examine the possibility of combining a batch-recirculated photoreactor with a ceramic membrane filter for heterogeneous photocatalysis applications. D-cargo red GS (GS) was used as the test substrate and titanium dioxide was used as photocatalyst for this study. The dark adsorption of GS on the TiO2 particle surface was also analyzed. The adsorption trends of GS at various initial concentrations followed the Langmuir isotherm trend. The GS were decolorized from 20% to 70% by the dark adsorption with various concentrations. The photodegradation of GS after the dark adsorption showed the behavior of Langmuir-Hinshelwood model. The variation of recirculation flow rate did not much influence photocatalysis. Variation tendencies of GS concentration were almost similar after about 90 minutes illumination in spite of the flow rate change. The values ofk (apparent first order rate constant) also varied with increase of the recirculation flow rate, but there were no observable significant differences between them.