• Ocean and Polar Research
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• v.36 no.2
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• pp.179-187
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• 2014

Directly searching for undiscovered hydrothermal vent sites is inefficient due to the practical difficulty of comprehensively imaging vent fields. Thus, most searches for hydrothermal vent sites rely on the detection of hydrothermal plumes from water column observation. Detecting and measuring the hydrothermal plumes are the most efficient way to infer the presence and distribution of hydrothermal vents. Both the array of vertical casting and lateral towing are the most common methods to discover hydrothermal plumes. In this study, we compared results of cast and tow-yo operations along the same section of a spreading center with a distance of 20.5 km in the North Fiji Basin for mapping hydrothermal plumes. Operation of CTD tow-yo provides a detailed pattern of plumes which enable us to locate the hydrothermal vents. On the other hand, identification of hydrothermal activity can be determined effectively by CTD cast with additional analysis of geochemical tracers. Reduction in the operating time is another advantage of CTD cast operation, especially for regional-scale survey. Our results show that the combination of CTD cast and tow-yo would improve the efficiency of the hydrothermal plume survey to locate new hydrothermal vent sites.

• Animal Bioscience
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• v.36 no.5
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• pp.818-828
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• 2023

Objective: The purpose of this study was to analyze the effect of the hydrothermal pretreatment of anaerobic digestion sludge cake (ADSC) of cattle manure on the solubilization of organic matter and the methane yield to improve the anaerobic digestion efficiency of cattle manure collected from the sawdust pens of cattle. Methods: Anaerobic digestion sludge cake of cattle manure was thermally pretreated at 160℃, 180℃, 200℃, and 220℃ by a hydrothermal pressure reactor, and the biochemical methane potential of ADSC hydrolysate was analyzed. Methane yield recovered by the hydrothermal pretreatment of ADCS was estimated based on mass balance. Results: The chemical oxygen demand solubilization degree (COD_s) of the hydrothermal hydrolysate increased to 63.56%, 67.13%, 70.07%, and 66.14% at the hydrothermal reaction temperatures of 160℃, 180℃, 200℃, and 220℃, respectively. Considering the volatile solids content obtained after the hydrothermal pretreatment, the methane of 10.2 Nm³/ton-ADSC was recovered from ADSC of 1.0 ton, and methane yields of ADSC hydrolysate increased to 15.6, 18.0, 17.4, and 17.2 Nm³/ton-ADSC. Conclusion: Therefore, the optimal hydrothermal reaction temperature that yielded the maximum methane yield was 180℃ based on mass balance, and the methane yield from cattle manure containing sawdust was improved by the hydrothermal pretreatment of ADSC.

• New & Renewable Energy
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• v.16 no.4
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• pp.83-91
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• 2020

In this study, the reusability of the Fenton oxidation solution was evaluated to reduce the cost of the pretreatment process. Biomass was sequential subjected to Fenton oxidation-hydrothermal treatment and enzymatic hydrolysis to produce monosaccharides. The liquid solution recovered after Fenton oxidation contained OH radicals with a concentration of 0.11 mol/L. This liquid solution was reused for a new Fenton oxidation reaction. After Fenton oxidation, hydrothermal treatment was performed under the same conditions as before, and 9.34-13.63 g/L of xylose was detected. This concentration was slightly lower than that of a fresh Fenton oxidation solution (16.51 g/L) but was higher than that obtained by hydrothermal treatment without Fenton oxidation (2.72 g/L). The degradation rate during hydrothermal pretreatment involving Fenton oxidation was 36.02%, which decreased (29.24-31.05%) slightly when the liquid solution recovered after Fenton oxidation was reused. However, the degradation rate increased compared to that measured from hydrothermal treatment without Fenton oxidation (15.21%). Moreover, the yield after enzyme hydrolysis decreased in the following order: fresh Fenton oxidation-hydrothermal treatment (89.64%) > Fenton oxidation with reused solution-hydrothermal treatment (74.84%) > hydrothermal treatment without Fenton oxidation (32.05%).

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1435-1438
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• 2009

Hydrothermal treatment of rice hull was hydrothermal carried out at 105, 110, $121^{\circ}C$ for 15, 30, 60 min, respectively, using a conventional autoclave. Antioxidant activity of the hydrothermal treated rice hull extract was evaluated by determining total phenol contents (TPC), 1,1-diphenyl-2-picylhydrazyl (DPPH) radical scavenging activity (RSA), reducing power, and ABTS RSA. TPC, DPPH RSA, reducing power, and 2,2-azinobis(3-ethylenebenzothiozoline-6-sulfonic acid) (ABTS) RSA of the extract were significantly increased with increasing treated temperature and time. For example, hydrothermal extracts at $121^{\circ}C$ for 60 min increased the TPC, DPPH RSA, reducing power, and ABTS RSA to 0.840 mg/mL, 64.77%, 1.437, and 92.11%, respectively, while those of the extracts treated at $105^{\circ}C$ for 60 min were 0.508 mg/mL, 51.23%, 0.819, and 45.22%, respectively. The results indicated that hydrothermal treatment of rice hull was very effective to increase phenolic compounds and antioxidant activity of rice hull extract.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.145-156
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• 2012

Seafloor hydrothermal system occurs along the volcanic mid-ocean ridge, back-arc spreading center, and other submarine volcanic regions. The hydrothermal system is one of the fundamental processes controlling the transfer of energy and matter between crust/mantle and ocean; it forms hydrothermal vents where various deepsea biological communities are inhabited and precipitates metal sulfide deposits. Hydrothermal systems at convergence plate boundaries show diverse geochemical properties due to recycle of subducted material compared to simple systems at mid-ocean ridges. Sulfur isotopes can be used to evaluate such diversity in generation and evolution of hydrothermal system. In this paper, we review the sulfur isotope composition and geochemistry of hydrothermal precipitates sampled from several hydrothermal vents in the divergent plate boundaries in the western Pacific region. Both sulfide and sulfate minerals of the hydrothermal vents in the arc and backarc tectonic settings commonly show low sulfur isotope compositions, which can be attributed to input of magmatic $SO_2$ gas. Diversity in geochemistry of hydrothermal system suggests an active role of magma in the formation of seafloor hydrothermal system.

• Economic and Environmental Geology
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• v.25 no.3
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• pp.225-232
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• 1992

The hydrothermal alteration is evaluated using multicomponent equilibrium calculations with the program CHILLER for the reactions between hydrothermal water and rhyolite at the temperature of $300^{\circ}C$ and pressure of 500 bars. The chemical-reaction model on the depositional processes of the sericitite confirms that the hydrothermal water-rock interaction(hydrothermal alteration) is the main mechanism of the sericitite formation. The principal change in the aqueous phase during the reaction is the pH increase. Overall trends for the major species are the increase in total molalities of K, Ca, $SiO_2$, Al, Mg, Fe, Na, and sulfide in solid phase with hydrothermal water-rhyolite reaction and the decrease of them in aqeous solution by precipitation of hydrothermal products. Quartz and sericite are the first minerals to form. The sequence of minerals to precipitate following them is chlorite, epidote, pyrite and microcline as water/rock ratio decreases. Although calculated results cannot duplicate the complexities of natural hydrothermal alteration, the calculation provides thermodynamic constraints on the natural process. The calculation results resemble those of experimental studies. Sericitite forms where pH decreases and water/rock ratio increases.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.811-816
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• 2000

This paper discussed hydrothermal reactivity of Ca(OH)2 and classified bituminous fly ashes which were collected at an electrostatic precipitator in coal fired power plant at 181$^{\circ}C$. The major products of hydrothermal reaction were tobermorite and hydrogrossularite because bituminous fly ashes contained Al2O3 content greater than 20 wt%. As increasing amount of Al2O3 content greater than 20 wt%. As increasing amount of Al2O3 in glass phases, formation of hydrogrossularite increased. Formation rate of crystalline tobermorite increased with content of finer particles, higher glass content and more Al2O3 in glass phases. There was a positive correlation between residue on 45${\mu}{\textrm}{m}$ sieve and hydrothermal reactivity of fly ash up to 3 hours. The hydrothermal reactivity of fly ash at 181$^{\circ}C$ for 12 hours was more affected by fineness than by glass content of fly ash.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.4
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• pp.172-178
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• 2007

Mica (muscovite) powders were synthesized by hydrothermal method (horizontal turning method). The hydrothermal conditions for the synthesis of mica were prepared by the ratio of $K_2O : Al(OH)_3 : SiO_2$ = 1 : 3 : 3 mol% as the starting materials with KOH (8 mol%) solution as the hydrothermal solvent and reaction temperature at $260^{\circ}C$ for 72hrs. The synthetic powder used for preparation of nano silver coated mica by vertical hydrothermal treatment. The hydrothermal conditions for the treated as nano silver coating were prepared by the synthetic powder as raw materials, triple distilled water ($0.5{\ell}$) solution as the hydrothermal solvent with nano silver sol (1,000 ppm) as the material of nano silver coating and reaction temperature at $160{\sim}260^{\circ}C$ for 72 hrs. After hydrothermal treatment, structural, judgment of nano silver coating and character of nano silver coated mica were examined by XRD, SEM, TEM-EDX and shake plask method.

• Ocean and Polar Research
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• v.42 no.1
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• pp.33-47
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• 2020

The bulk and partition geochemistry was studied in two sediment cores collected from the axial valley of the north-central Fonualei Rift and Spreading Center (FRSC), Lau back-arc Basin, southwest Pacific. The sediments consist of mostly volcanic ash, although minor amounts of biogenic and other components were present in some intervals. The major element composition of bulk sediments recalculated to a carbonate-free basis was in good agreement with the magma compositions of the adjacent Tofua Arc and the FRSC, with only significant difference in Mn content. The enrichment of Mn and other associated elements (e.g. Cu, Co, Ni, and P) is attributed to hydrothermal input to the sediments, as evidenced by their significant partitioning in the non-detrital phases according to the partition geochemistry. Hydrogenetic and diagenetic inputs were assessed to be relatively insignificant. Estimated hydrothermal Mn fluxes during the Holocene ranged between 5.0 and 37.1 mg cm^-2 kyr^-1, with the higher values in younger sediments, suggesting enhanced hydrothermal activity. The hydrothermal Mn fluxes comparable to or higher than those reported from other spreading centers with strong hydrothermal activities may indicate the presence of unknown hydrothermal vent sites and/or topographic restriction on the dispersal of hydrothermal plumes in the northern part of the FRSC.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.57-63
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• 2015

Recently, Korea's municipal wastewater treatment plants generated amount of wastewater sludge per day. However, ocean dumping of sewage sludge has been prohibited since 2012 by the London dumping convention and protocol and thus removal or treatment of wastewater sludge from field sites is an important issue on the ground site. The hydrothermal carbonization is one of attractive thermo-chemical method to upgrade sewage sludge to produce solid fuel with benefit method from the use of no chemical catalytic. Hydrothermal carbonization improved that the upgrading fuel properties and increased materials and energy recovery, which is conducted at temperatures ranging from 200 to $350^{\circ}C$ with a reaction time of 30 min. Hydrothermal carbonization increased the heating value though the increase of the carbon and fixed carbon content of solid fuel due to dehydration and decarboxylation reaction. Therefore, after the hydrothermal carbonization, the H/C and O/C ratios decreased because of the chemical conversion. Energy retention efficiency suggest that the optimum temperature of hydrothermal carbonization to produce more energy-rich solid fuel is approximately $200^{\circ}C$.