• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.553-559
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• 2009

One of zeolitic imidazolate framework materials (ZIF), ZIF-8, has been synthesized with microwave irradiation and conventional electric heating at $140{\sim}180^{\circ}C}$. ZIFs are porous crystalline materials and are similar to metal organic framework (MOF) materials because both ZIFs and MOFs are composed of both organic and metallic components. ZIFs are very stable and similar to zeolites because ZIFs have tetrahedral networks. ZIF-8, with a decreased crystal size, can be synthesized rapidly with microwave irradiation. The microwave synthesis of ZIF-8 is completed in 4 h at $140{^{\circ}C}$ and the reaction time is decreased by about 5 times compared with the conventional electric heating. The ZIF-8 obtained by microwave heating has larger surface area and micropore volume compared with the ZIF-8 synthesized with conventional electric heating. It can be confirmed that ZIF-8s show type-I adsorption isotherms, explaining the microporosity of the ZIF-8s. Based on FTIR and TGA results, it can be understood that the ZIF-8s have similar bonding and thermal characteristics irrespective of heating methods such as microwave and conventional heating.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.559-568
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• 2013

Surface compaction significantly impacts runoff and soil erosion under rainfall since it leads to changes of soil physical characteristics such as increase of bulk density and shear stress, change of microporosity, and decrease of hydraulic conductivity. This study addressed surface compaction effects on runoff and soil loss from bare and disturbed soils that are commonly distributed on construction sites. Thirty-six rainfall simulations from three replicates of each involving rainfall intensities (68.5 mm/hr, 95.6 mm/hr) and plot gradients ($5^{\circ}$, $12.5^{\circ}$, $20^{\circ}$) were conducted to measure runoff and soil loss for two different soil surface treatments (compacted surface, non-compacted surface). Compacted surface increased significantly soil bulk density and soil strength. However, the effect of surface treatments on runoff changed with rainfall intensity and plot gradient. Rainfall intensity and plot gradient had a positive effect on mean soil loss. In addition, the effect of surface treatments on soil loss responded differently with rainfall intensity and plot gradient. Compacted surfaces increased soil loss at gentle slope ($5^{\circ}$) while they decreased soil loss at steep slope ($20^{\circ}$). These results indicate that there exists transitional slope range ($10{\sim}15^{\circ}$) between gentle and steep slope by surface compaction effects on soil loss under disturbed bare soils and simulated rainfalls.

• Clean Technology
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• v.28 no.3
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• pp.249-257
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• 2022

The adsorption equilibria of nitrogen on a region of nanoporous carbonaceous adsorbent with local molecular orientation (LMO) were calculated by grand canonical Monte Carlo simulation at 77.16 K. Regions of LMO of identical size were arranged on a regular lattice with uniform spacing. Microporosity was predominately introduced to the model by removing successive out-of-plane domains from the regions of LMO and tilting pores were generated by tilting the basic structure units. This pore structure is a more realistic model than slit-shaped pores for studying adsorption in nanoporous carbon adsorbents. Their porosities, surface areas, and pore size distributions according to constrained nonlinear optimization were also reported. The adsorption in slit shaped pores was also reported for reference. In the slit shaped pores, a clear hysteresis loop was observed in pores of greater than 5 times the nitrogen molecule size, and in capillary condensation and reverse condensation, evaporation occurred immediately at one pressure. In the LMO pore model, three series of local condensations at the basal slip plane, armchair slip plane and interconnected channel were observed during adsorption at pore sizes greater than about 6 times the nitrogen molecular size. In the hysteresis loop, on the other hand, evaporation occurred at one or two pressures during desorption.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.107-114
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• 2024

In order to produce high-yield pitch-based activated carbon, pitch was synthesized by blending pyrolysis fuel oil (PFO) and coal-tar. Pitch was synthesized by varying the amount of coal-tar from 0~20% compared to PFO and reacting at 380~420 ℃ for 3 h. The synthesized pitch had a softening point between 80 and 260 ℃, and yields ranged from 10 to 40%. At all synthesis temperatures, as the coal-tar blending ratio increased, the yield increased and the softening point decreased. After considering the selected pitches (softening points: 230~260 ℃), pitches containing coal-tar were more volatile at a low boiling point and had a higher residual carbon content. This is a difference in the composition of coal-tar and PFO, and it was con- firmed that coal-tar has a lot of aromatics and PFO has a lot of aliphatics. The selected pitch was heated to 950 ℃ in a tubular reactor and physically activated with steam for 1 hour. Activated carbon containing coal-tar showed higher yield and microporosity compared to only PFO. In this study, the effect of increasing activated carbon yield by blending pitch raw materials was confirmed, and the physical activation characteristics according to the coal-tar mixing ratio were examined.