• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.7
• /
• pp.1295-1305
• /
• 2000

Status of the contaminated sediments in Lake Paldang was investigated. Sediment samples were taken at 34 points and analyzed in terms of ignition loss, CODer, total P and total N. The contamination level did not show any significant variation with depth of the sediments, which indicated the contaminants were recalcitrant. The type of P in the sediment was analyzed, and the sum of adsorbed P and NAI-P, that can be re-solubilized under the reductive condition, was found to be 20-30% of the total P. From the analysis of the water quality change along with the flowing path, it would be concluded that the effect of the sediments on the water quality is insignificant yet in Lake Paldang. However, long term analysis covering at least four seasons should be continued in order to get a more reliable conclusion. A depth profile map of the sediment in Lake Paldang was provided.

• Journal of the Korean Wood Science and Technology
• /
• v.52 no.2
• /
• pp.101-117
• /
• 2024

The conversion characteristics of the major components of Liriodendron tulipifera were investigated during acid-catalyzed organosolv pretreatment. Glucan in L. tulipifera was slowly hydrolyzed, whereas xylan was rapidly hydrolyzed. Simultaneous hydrolysis and degradation of xylan and lignin occurred; however, after complete hydrolysis of xylan at higher temperatures, lignin remained and was not completely degraded or solubilized. These conversion characteristics influence the structural properties of glucan in L. tulipifera. Critical hydrolysis of the crystalline regions in glucan occurred along with rapid hydrolysis of the amorphous regions in xylan and lignin. Breakdown of internal lignin and xylan bonds, along with solubilization of lignin, causes destruction of the lignin-carbohydrate complex. Over a temperature of 160℃, the lignin that remained was coalesced, migrated, and re-deposited on the surface of pretreated solid residue, resulting in a drastic increase in the number and content of lignin droplets. From the results, the characteristic conversions of each constituent and the changes in the structural properties in L. tulipifera effectively improved enzymatic hydrolysis in the range of 140℃-150℃. Therefore, it can be concluded that significant changes in the biomass recalcitrance of L. tulipifera occurred during organosolv pretreatment.

• Resources Recycling
• /
• v.16 no.3 s.77
• /
• pp.44-49
• /
• 2007

In the present work, the high temperature oxygen pressure leaching behavior of chalcopyrite was studied in sulfuric acid solution. The influence of leaching time, temperature and oxygen partial pressure on leaching process were examined. Leaching rate of copper increased significantly with increasing leaching temperature. Copper recovery reached 87.1% within 2 hours at $200^{\circ}C$ and 10 atm oxygen pressure, while most of the solubilized iron readily re-precipitates as hematite($Fe_2O_3$). It was confirmed that e main leach reaction of chalcopyrite occurred through oxidation with oxygen under oxygen pressure and high temperature(above $150^{\circ}C$). Because sulfur was oxidized entirely to sulfate, passivating elemental sulfur layer was not formed.