Kwang Seop Kim

Occlusion potential of zeolites for mixed and non-nitrate salts

Abstract Occluded salts in the form of salt complexes exhibit the interesting properties unattainable in bulk state. In this study, occlusion of non-nitrate salts and co-occlusion of mixed nitrate salts were attempted to further expand occlusion potential of zeolites. The non-nitrate salts such as KClO 3 and KH 2 PO 4 were occluded by mordenite, although they do not establish stable molten state. Their occlusions were confirmed by 27 Al NMR spectra, N 2 adsorption/desorption isotherms and thermal analyses. The occluded amounts were relatively less compared to those of nitrate salts. On the other hand, thermal treatment of Na–P1 with a mixture of NH 4 NO 3 and KNO 3 resulted in co-occlusion of both NH 4 NO 3 and KNO 3 by Na–P1 below the melting temperature of KNO 3 . The salts in solid state could be introduced into and occluded by zeolites through the interaction with the molten salt present in the salt mixture. The use of salt mixture could lead to co-occlusion of the salts that could be hardly applicable to salt occlusion. Therefore, this study clearly shows that a variety of salts could be applied to salt occlusion by zeolites.

Adsorbate-dependent uptake behavior of topographically bi-functionalized ordered mesoporous silica materials

Abstract Novel behaviors such as adsorbate-dependent pore opening and functionality-controlled uptake have been accomplished by the bifunctionalized ordered mesoporous silica developed here. SBA-11 was topographically functionalized with two different functional groups by step-wise functionalization. Bulky and flexible tert-butylphenethyl (BP) groups were topographically grafted around the pore entrance and on the external surface, while small dimethyl (DM) groups were attached on the inner pore surface. The resulting bifunctionalized SBA-11 exhibited the selective malathion scavenger, which was not observed by the corresponding mono-functionalized SBA-11s. The uptake behaviors of the functionalized SBA-11s for malathion and toluene strongly suggest that the bulky and flexible BP groups are locally grafted around the pore entrance to act as a functional pore window. The interaction among the adsorbate, BP and DM groups induces a specific rearrangement of functional pore window which leads to the discriminative uptake. Therefore, the functionalized OMMs equipped with the pore window, the nanosized functional vessels, could be developed into the adsorbate-discriminating adsorbents for highly selective removal/recovery of specific organic molecules.

Effects of Continuous Application of Green Manures on Microbial Community in Paddy Soil

Green manure crops have been well recognized as the alternative for chemical fertilizer, especially N fertilizer, because of its positive effect on soil and the environment. Hairy vetch and green barley are the most popular crops for cultivation of rice in paddy field. This study was conducted to evaluate effects of hairy vetch and green barley on soil microbial community and chemical properties during short-term application (three years). For this study, treatments were composed of hairy vetch (Hv), green barley (Gb), hairy vetch + green barley(Hv+Gb), and chemical fertilizer without green manure crops (Con.). Hv+Gb treatment showed the highest microbial biomass among treatments. Principal component analysis (PCA) showed that PC1 (73.0 %) was affected by microbial biomass and PC2 (21.5 %) was affected by fungi, cy19:0/18:1ω7c (stress indicator). Combined treatment with hairy vetch and green barley could be more efficient than green manure crop treatment as well as chemical fertilizer treatment for improvement of soil microorganisms.

Post-isomorphic substitution of trivalent metal cations for Ca2+ in portlandite crystals

Isomorphic substitution, position replacement of one cation by another of similar size, leads to incorporation of a variety of cations into solid crystals without any significant changes to the primary crystal structures. To date, isomorphic substitution has been known to take place almost exclusively via co-crystallization of the cations during formation of the crystals. We report here the discovery of isomorphic substitution of trivalent metal cations for Ca2+ ions in portlandite crystals at room temperature as evidenced by the transient appearance of metastable phase, the formation of Ca-based layered double hydroxides at high pH, the distinct shift of suspension pH after phase transition, and the in situ topochemical reaction. This post-crystallization isomorphic substitution provides an innovative pathway for the synthesis of materials through chemical manipulation of crystals as well as a new insight into interpretation on their weathering and transformation processes.

Assessment of Sustainable Production on Paddy Field Treated with Green Manure Crops Using Sustainability Index

Assessment of sustainable production on a cropland can help to determine the most proper management practices. In this study, we evaluated the sustainable production on paddy field treated with green manure crops using sustainability index which based on nutrient index, microbiological index, and crop index related to nutrient-supplying capacity. Especially choosing appropriate indicators from a minimum data set (MDS) were used the principal components analysis (SI-2) as well as expert opinion (SI-1) usually used in sustainability index. Six treatments including the two tillage treatments and two green manure crops were investigated as follows; (i) moldrotary + rotary tillage without green manure crop (Con), with (ii) hairy vetch (Con-HV), and (iii) hairy vetch + green barely (Con-HV+GB), (iv) rotary tillage without green manure crop (Rot), with (ii) hairy vetch (Rot-HV), and (iii) hairy vetch + green barly (Rot-HV+GB). Con-HV and Rot-HV in SI-1 were maintained sustainability while Rot-HV and Rot-HV+GB in SI-2. Especially, treatments (Con and Rot) without green manure crops were more unsustainable than with green manure crops because of the low value of microbiological and crop index than with green manure crops. Meanwhile, sustainability indices and grain yield had the high correlation values (R²=0.756 and 0.928 in SI-1 and SI-2, respectively). These results meant that application of green manure crops such as hairy vetch could improve both yield and soil quality in paddy.

Release Pattern of Urea from Metal-urea-clay Hybrid with Montmorillonite and Its Impact on Soil Property

Urea intercalated into montmorillonite (MT) exhibits remarkably enhanced N use efficiency, maintaining its fast effectiveness. This study dealt with the release property of urea from metal-urea-clay hybrid with MT (MUCH) under continuous-flow conditions and the cumulative impacts of its successive application on physicochemical properties of soils. Releases of urea were completed within 4 hrs under continuous-flow condition regardless of the types and the leaching solutions. However, urea release property was significantly affected by both the form of fertilizer and the presence of electrolytes in solution. The fast release property of urea from MUCH in continuous-flow condition was not significantly affected by soil properties such as soil pH and soil texture. In addition, its successive application did not lead to any noticeable change in soil physicochemical properties, water stable aggregate rate, water holding capacity and cation exchange capacity in both sandy loam and clay loam soils. Therefore, this study strongly supported that urea intercalated into MT could be applied as fast-effective N fertilizer, in particular for additional N supply.

Effect of Legume Cover Crops and Nitrogen Fertilization Rates on Yield and Nitrogen Use Efficiency of Waxy Corn (Zea mays L.) in No-Tillage System

The adoption of legume cover crops in no-tillage system can contribute to improve soil fertility by providing several benefits, including reduction in soil erosion, suppression of weed growth and N supply to subsequent crops. We conducted a field study to investigate the effect of cover crops and nitrogen fertilization rates on yield and nitrogen use efficiency of waxy corn (Zea mays L.) in no-tillage upland field. Two legume cover crops, hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnuturn L.) were mechanically terminated with roller in early June. For each cover crop treatment, nitrogen (N) fertilizer was applied at three different rates (145, 72.5 and 0 kg N ha-1 ). The growth and yield characteristics of corn were significantly affected by the N fertilization rates in crimson clover plots, which suggest N mineralization from the cover crop residue was not sufficient. In contrast, N fertilization rates had no significant effect on growth and yield of corn in hairy vetch plots, indicating that the amount of N released from the cover crop is large enough to meet most of the N requirement of corn. However, the application of N fertilizer in hairy vetch cover plots resulted in slight increase of crop yield, though not statically significant, and high levels of N concentration in corn plant tissue possibly due to luxury consumption of N. Organic residues on the soil surface in hairy vetch cover plots had substantial amounts of N after harvest, ranging from 100 to 116 kg N ha -1 , which is presumably retained during winter season and released by microbial mineralization in subsequent year. The highest nitrogen yield efficiency was achieved in the plot with hairy vetch cover and no N fertilizer application, followed by the plot with hairy vetch cover and 72.5 kg N ha -1 fertilization rate. In conclusion, hairy vetch showed better performance in corn productivity as compared with crimson clover. In addition, it was concluded that the application of N fertilizer between 0 and 72.5 kg N ha -1 in combination with hairy vetch cover crop might be most efficient for corn yield under no-tillage system with climatic and soil characteristics similar to those of the experimental site.

Evaluation on Soil Characterization in Paddy Treated with Different Green Manure Crops and Tillage Method by Ordination Technique

Ordination has been recognized useful method to analyze the effects of multiple environmental factors on dozens of species in vegetation ecology because of summarizing community data by producing a low-dimensional graphics. Main objective of this study was the application of ordination method, especially principal components analysis (PCA), to analyze the soil characterization on paddy treated by different green manure crops and tillage methods. Treatments included the three tillage treatments and two green manure crops as the following; (ⅰ) moldrotary + rotary tillage without green manure crop (Con), with (ⅱ) hairy vetch (ConHv), and (ⅲ) hairy vetch + green barely (ConHvGb), (ⅳ) rotary tillage without green manure crop (Rot), with (ⅴ) hairy vetch (RotHv), and (ⅵ) hairy vetch + green barly (RotHvGb), and (ⅶ) no-tillage (Notill). Vectorial distance result from PCA of soil properties including physical, chemical, and microbial properties showed the two main difference. Firstly, soil properties among plots without green manure were strongly affected by tillage strength [Vectorial distance: Con-Notil (5.88) 〉Rot-Notill (4.58)] at PC1 (35.0%) axis. But it was difficult to find the fixed trend among plots when green manure crop was added in plot. Nevertheless, two groups were separated by adding green manure crop at PC2 (29.2%) axis. These results show that PCA ordination methods could be used the research for change of soil characterization.