• Advances in Traditional Medicine
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• v.5 no.1
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• pp.43-47
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• 2005

Jack bean urease was immobilized on gelatin beads with the help of glutaraldehyde. The optimum immobilization (67.6%) was obtained at 30mg/ml gelatin concentration, 0.5 mg/bead enzyme protein concentration, 1 % glutaraldehyde and at $4^{\circ}C$ incubation temperature. The $t_{1/2}$ of immobilized urease was approximately 90 days at $4^{\circ}C$ compared with $t_{1/2}$ of 20 days for the soluble urease, under identical condition. The apparent optimum pH shifted from 7.3 to 8.0 when the urease was immobilized. The optimum stability temperature of immobilized urease was found to be $60^{\circ}C$ while that of soluble urease was $45^{\circ}C$. Time-dependent thermal inactivation studies showed monophasic kinetics for soluble urease and immobilized urease at $70^{\circ}C$, respectively. The immobilized urease beads stored at $4^{\circ}C$ showed practically no leaching over a period of 30 days. Here we are presenting an easy and economical way of immobilizing urease on the gelatin beads making it suitable for various applications.

• Resources Recycling
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• v.15 no.5 s.73
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• pp.38-46
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• 2006

The removal of arsenic(V) using four different natural minerals were evaluated. Parameters like contact time, pH, adsorbent dosages, and As(V) concentration were optimized. The kinetics of adsorption was observed to be fast and reached equilibrium within 2h. As(V) adsorption on studied minerals was dependent on pH and followed a pseudo-second-order reaction model. For kaolin, maximum adsorption was found at pH 5.0. Whereas, in case of other three minerals, a pH range of 6.0-7.0 was found to be the best for As(V) adsorption. The maximum adsorption capacity (Q) was calculated by fitting Langmuir equation to the adsorption isotherms obtained under a specified condition. From the slope of best fit, the Q values were calculated to be 2.07, 2.15, 1.95 and 0.86 mg As(V)/g of bauxite, wad, iron ore and kaolin, respectively. Desorption of As(V) from loaded materials was dependent on the type of leaching reagents used. Based on the results, it was found that among the studied natural minerals, wad was the best As(V) adsorbent.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.345-349
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• 2003

The quantity, process and kinetics of di-(2-ethylhexyl)phthalate (DEHP) migration in the 30/70 and 40/60 poly(vinylchloride) (PVC)/DEHP blends were investigated using gas chromatograph. A thin and flexible PVC sheet was soaked in surrounding medium (SM) of water/ethanol mixture and acetonitrile with constant stirring to release DEHP. By observed concentration of DEHP in the SM, it is found that acetonitrile is more intense in DEHP migration than water/ethanol mixture. In addition the amount of extracted DEHP is proportional to the leaching temperature and added ratio of DEHP. The behavior of DEHP migration from flexible PVC sheets was described by the Ficks's law with $2.72-10.1\;{times}\;10^{-10}$ cm²/s of the diffusion coefficients.

• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.72-79
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• 1997

Adsorption, leaching, and retention of the Flupyrazofos(KH-502), a new active ingredient for insecticide, in the soils under laborarory and field conditions were investigated to provide the basic data for the safety use and to assess a secondary impact of this insecticide on soil and water environments. A significant power function relation was found between the adsorbed KH-502 and time, representing that 45% of the added KH-502 was adsorbed within 30 min. but a quasiequilibrium was reached after 6 to 12 hr with a slower adsorption. Adsorption phenomena followed th first-order kinetics and time required for 50% adsorption was 5.8 hr. The equilibrium adsorption isotherm was explained by the Freundlich equation and was classified as S-type. The amounts of KH-502 leached through the soil column (C) as compared to initial conc. ($C_0$) were very low and these relative concentrations ($C/C_0$) were 0.073 and 0.017 in SL and CL soils, respectively. The residual conc. of KH-502 in the surface soil was comparatively low and decreased with time. Half-lives of KH-502 in the surface soil was comparatively low and decreased with time. Half-lives of KH-502 under the field conditions were estimated to be 20 and 18 days in the SL and CL soils, respectively. The KH-502 cone, transported to the subsurface soils was extremely low. These results demonstrate that KH-502 has a low pollution risk potential to the surrounding environment as far as it is used following the recommended guideline.

• Resources Recycling
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• v.22 no.1
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• pp.64-71
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• 2013

Mineral carbonation has been proposed as a possible way for $CO_2$ sequestration. The electric arc furnace slags consist of calcium, magnesium and aluminum silicates in various combinations. If they could be used instead of natural mineral silicates for carbonation, considerable energy savings and $CO_2$ emissions reductions could be achieved. Indirect aqueous carbonation of the slags consists of two steps, extraction of calcium and carbonation. Acetic acid leaching of electric arc furnace slags had been already studied to extract Ca in them, but it was reported that the carbonation of the extracted $Ca^{2+}$ in the leached solution would suffer from too slow kinetics, even at high pressure of $CO_2$. In this work, to develop more efficient extraction of the electric arc furnace slags, hydrochloric acid leaching to separate calcium from them was studied, and the results were compared with the acetic acid ones. The phase boundary between $Ca^{2+}$ and $CaCO_3$ in the solution with pH was determined by thermodynamic calculations. Hydrochloric acid was more effective than acetic acid for the extraction of Ca in electric arc furnace slag, and there is a possibility to recycle an unreacted hydrochloric acid in the leached solution by electrolysis or evaporation.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.1
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• pp.37-43
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• 1998

Batch experiments were conducted to study the dissolution behavior of gasoline components. First, the dissolution kinetics of gasoline components and the applicability of Raoult's law in predicting their solubilities were investigated. In addition, the effects of compositional change of gasoline due to evaporization on the solubilities of individual components and TPH were determined. The kinetics of gasoline-water man transfer was found to be very similar for most components except for MTBE, which is a major additive for commercial gasoline. At equilibrium, the gasoline-water partitioning coefficients of individual components showed a log-linear relationship with their pure solubilities, though the slope was a little less than that predicted by Raoult's law. The concentrations of the individual components in the gasolines concentrated by volatilization could be characterized by the initial increase followed by substantial decrease. Almost the same behavior was observed for their solubilities. The total solubility (TPH) of gasoline decreased rapidly with the initial volume reduction and gradually decreased afterwards. The solubilities of BTEX, the major regulatory compounds, decreased even faster than the TPH solubilities. It was concluded that the compositional change of gasoline by volatilization may greatly affect their leaching potential and the toxicity of the contacting groundwater. The toxicity reduction efficiency by evaporating gasoline could be much more than the mass removal efficiency.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.561-574
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• 2009

Unsaturated/saturated groundwater flow and solute transport model, VSFRT2D(Variable Saturated Flow and Reactive Transport model) was developed considering effects of pumping, irrigation, and denitrification. VSFRT2D employed Richards equation as governing equation for groundwater flow and previously existing unsaturated models modified by including computational procedure of evapotranspiration at surface using Thornthwaite method when precipitation doesn't occur. Bioremediation processes based on monod kinetics are described using four nonlinear contaminant transport equations and three nonlinear microbes transport equations. The developed model was applied to field data in Hongsung area contaminated with nitrate. In order to identify the effect of precipitation, pumping, evapotranspiration, irrigation, fertilizer application, and various bioremediations on groundwater flow and contaminant transport, individual processes were separated and simulated. Then all results obtained from the individual processes are compared with each other. The simulation results show that bioremediation had a negligible effect on nitrate concentration change. However, pumping for irrigation, precipitation, and nitrogen fertilizer application showed profound influences on nitrate concentration change.

• Carbon letters
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• v.15 no.1
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• pp.57-66
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• 2014

Three activated carbons (ACs) were prepared using NaOH (N) as an activating agent. Hydrofluoric acid pre-leached rice husk was used as a precursor. After leaching, the precursor was washed with distilled water, dried, crushed, and then sieved; a size fraction of 0.3-0.5 mm was selected for carbonization in the absence of air at $600^{\circ}C$. The carbonization product (LC) was mixed with NaOH at ratios of 1:2, 1:3, and 1:4 (wt of LC: wt of NaOH) and the produced ACs after activation at $800^{\circ}C$ were designated NLC21, NLC31, and NLC41, respectively. Surface and textural properties were determined using nitrogen adsorption at $-196^{\circ}C$, scanning electron microscopy images, thermogravimetric analysis, and Fourier transform infrared spectra. These ACs were used as adsorbents for lead(II) from aqueous solutions. The effects of the textural properties and the chemistry of the carbon surfaces were investigated and the impact of the operation conditions on the capacity for lead(II) sorption was also considered. Modification of NLC41 with $H_2O_2$ and $HNO_3$ gave two other adsorbents, $H_{NLC41}$ and $N_{NLC41}$ respectively. These two new samples exhibited the highest removal capacities for lead(II), i.e.117.5 and 128.2 mg/g, respectively. The adsorption data fitted the Langmuir isotherm and the kinetic adsorption followed pseudo-second order kinetics. The thermodynamic parameters have been determined and they indicated a spontaneous endothermic process.

• Korean Journal of Environmental Agriculture
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• v.20 no.4
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• pp.269-276
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• 2001

Several experiments including persistence, distribution, leaching, and terminal residue trials were carried out to investigate the behavior of cyclosulfamuron in rice paddies. Cyclosulfamuron was gradually dissipated in two different soils showing the first-order kinetics. Half-lives of the herbicide were calculated to be $17{\sim}30$ and $14{\sim}16$ days under field and laboratory conditions, respectively. In the paddy soil/water system, the residue tended to reside more in the soil phase as time elapsed. Cyclosulfamuron was less persistent in paddy water than in soil with half-lives of 10 and 19 days, respectively. No cyclosulfamuron was leached below 20 cm-deep soil during water percolation with 50 cm hydraulic head, while some downward mobility was observed within the soil column. When EC and SC formulations of cyclosulfamuron were applied to the paddy field at 120 or 150-day pre-harvest intervals, its terminal residues in hulled rice were all less than 0.01 mg/kg, irrespective of formulation type and application timing. In rice straw, however, some residues were found at $<0.02{\sim}0.05$ mg/kg as SC formulation was applied. Rapid dissipation, restricted mobility, and low terminal residues of cyclosulfamuron in rice paddies suggest that no significant residues would be transported or carried over to the non-target environment.

• Resources Recycling
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• v.29 no.5
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• pp.38-47
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• 2020

In this study, factors affecting the adsorption reaction for the separation/recovery of V and W using Lewatit monoplus MP 600, a strong basic anion exchange resin, from the leachate obtained through the soda roasting-water leaching process from the spent SCR DeNO_X catalyst investigated and the adsorption mechanism was discussed based on the results. In the case of the mixed solution of V and W, both ions showed a high adsorption ratio at pH 2-6, but the adsorption of W was greatly reduced at pH 8. In the adsorption isothermal experiment, both V and W were fitted well at the Langmuir adsorption isotherm, and the reaction kinetics were fitted well at pseudo-second-order. As a result of conducting an adsorption experiment by adjusting the pH with H₂SO₄ to remove Si, which inhibits the adsorption of V and W from the leachate, the lowest W adsorption ratio was shown at pH 8.5. Desorption of W was hardly achieved in strongly acidic solutions, and desorption of V was well performed in both strongly acidic and strongly basic solutions.