• Journal of the Korean Applied Science and Technology
• /
• v.18 no.3
• /
• pp.174-179
• /
• 2001

The spinel $Fe_{3}O_{4}$ powders were synthesized using 0.2 $M-FeSO_4{\cdot}7H_{2}O$ and 0.5 M-NaOH by oxidation in air and the spinel $LiMn_{2}O_{4}$ powders were synthesized at 480 $^{\circ}C$ for 12 h in air by a sol-gel method using manganese acetate and lithium hydroxide as starting materials. The synthesized $LiMn_{2}O_{4}$ powders were mixed at portion of 5, 10, 15 and 20 wt% of $Fe_{3}O_{4}$ powders using a ball-mill. The mixed catalysts were dried at room temperature for 24 hrs. The mixed catalysts were reduced by hydrogen gas at 350 $^{\circ}C$ for 2 h. The carbon dioxide decomposition rates of the mixed catalysts were 90% in all the mixed catalysts but the decomposition rate of carbon dioxide was increased with adding $LiMn_{2}O_{4}$ powders to $Fe_{3}O_{4}$ powders.

• Applied Chemistry for Engineering
• /
• v.22 no.2
• /
• pp.185-189
• /
• 2011

In this work, nano-sized M-ferrites (M=Co, Ni, Cu, Zn) for the decomposition of carbon dioxide were synthesized by the chemical co-precipitation. From the thermogravimetric analysis, it was clear that the maximum weight loss of each sample took place below $350^{\circ}C$. High temperature calcination resulted in more systematic crystallines, smaller specific surface area and larger particle size. An analysis by FTIR in the range of $375{\sim}406cm^{-1}$ revealed the presence of chelates at the octahedral site, which implies the formation of spinel structure in the ferrites. The current work showed that a $500^{\circ}C$ is the optimum heat treatment temperature of metal ferrites for $CO_2$ decomposition reaction.

• The Journal of Natural Sciences
• /
• v.1
• /
• pp.47-59
• /
• 1987

The thermal decomposition mechanism of BaTiO($$C_2$$O_4$)_2$ $4H_2$O has been investigated employing TG, DTG, and DTA techniques. The intermediate compounds and the gaseous products of decomposition were examined by IR spectrometer and X-ray analyser. The decomposition proceeds through five steps. The first step which is the dehydration of the tetrahydrate is followed by the decomposition of oxalate groups. During the second decomposition, half a mole of carbon monoxide is evolved. The oxalate groups are completely destroyed in the range $260~460^{\circ}C$, resulting in the formation of a carbonate which retains free carbon dioxide in the matrix . the final decomposition of the carbonate takes place between $650~750^{\circ}C$ and yields $BaTiO_3$.

• Journal of Korean Society on Water Environment
• /
• v.18 no.3
• /
• pp.271-282
• /
• 2002

The sonochemical process has been applied as a treatment method to investigate its effect on the decomposition of humic substances (HS). The reaction kinetics and mechanisms in the process of sonochemical treatment for humic substances in wastewater have also been discussed. It was observed that the metal ions such Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final step of the reaction is the conversion of organic acids to carbon dioxide.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.10 no.S_3
• /
• pp.127-137
• /
• 2001

The sonochemical Process has been applied as a treatment method and was investigated its effect on the decomposition of humic substances(HS). The reaction kinetics and mechanisms in the Process of sonochemical treatment for humic substances(HS) in wastewater have also been discussed. It was observed that the metal ions such as Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The mechanism of radical reaction is controlled by an oxidation process. The radicals are so reactive that most of them are consumed by HS radicals and hydroxyl radicals can be acted on organic solutes by hydroxyl addition, hydrogen abstraction, and electron transfer. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final steps of the reaction are the conversion of organic acids to carbon dioxide.

• Korean Journal of Materials Research
• /
• v.19 no.9
• /
• pp.481-487
• /
• 2009

The photocatalysts of Fe-ACF/$TiO_2$ compositeswere prepared by the sol-gel method and characterized by BET, XRD, SEM, and EDX. It showed that the BET surface area was related to adsorption capacity for each composite. The SEM results showed that ferric compound and titanium dioxide were distributed on the surfaces of ACF. The XRD results showed that Fe-ACF/$TiO_2$ composite only contained an anatase structure with a Fe mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in Fe-ACF/$TiO_2$ composites. From the photocataytic degradation effect, $TiO_2$ on activated carbon fiber surface modified with Fe (Fe-ACF/$TiO_2$) could work in the photo-Fenton process. It was revealed that the photo-Fenton reaction gives considerable photocatalytic ability for the decomposition of methylene blue (MB) compared to non-treated ACF/$TiO_2$, and the photo-Fenton reaction was improved by the addition of $H_2O_2$. It was proved that the decomposition of MB under UV (365 nm) irradiation in the presence of $H_2O_2$ predominantly accelerated the oxidation of $Fe^{2+}$ to $Fe^{3+}$ and produced a high concentration of OH radicals.

• Horticultural Science & Technology
• /
• v.29 no.6
• /
• pp.575-582
• /
• 2011

This experiment was conducted to study the qualitative changes of grafted cactus after harvest and to examine the decomposition characteristics of pathogenic fungi which occurs or grows during the simulated shipping period. Plant materials with four varieties of Gymnocalycium mihanovichii var. friedrichii including, 'Hukwang', 'Huhong', 'Hwangwol', 'Yeunhwa' and two varieties of Chamaecereus silvestrii f. variegate such as 'Goldcrown' and 'Yellowcrown' were used. During the simulated shipping period, the fresh-weight, bulb diameter, carbon dioxide emission rate, and decomposition rate were observed. The regeneration rate and decomposition rate were observed for the grafted cactuses that were placed in a greenhouse environment with a temperature of $28{\pm}12^{\circ}C$ and humidity of $36{\pm}15.3%$ after 40 days of simulated shipping. There were reductions in the fresh-weight and bulb diameter in every variety as time passed while the carbon dioxide emission rate showed no meaningful difference by each variety. Furthermore, the decomposition rate in the scion was higher than in the stock. According to the analysis of pathogenic fungi by decomposition characteristics, Alternaria sp., Cladosporium sp., Colletotrichum sp., Fusarium sp., Penicillium sp. in G. mihanovichii var. friedrichii were found and Alternaria sp., Bipolaris sp., Cladospoirum sp. in C. silvestrii f. variegate were identified. Therefore, to maintain and improve the quality of grafted cactus, it is necessary to analyze the factors of decomposition from the time of harvest until the point of export and develop a process technology to minimize the decomposition rate.

• Journal of Sensor Science and Technology
• /
• v.22 no.3
• /
• pp.197-201
• /
• 2013

This paper describes the fabrication and characterization of graphene based carbon dioxide ($CO_2$) gas sensors. Graphene was synthesized by thermal decomposition of SiC. The resistivity $CO_2$ gas sensors were fabricated by pure graphene and graphene decorated Au nanoparticles (NPs). The Au NPs with size of 10 nm were decorated on graphene. Au electrode deposited on the graphene showed Ohmic contact and the sensors resistance changed following to various $CO_2$ concentrations. Resulting in resistance sensor using pure graphene can detect minimum of 100 ppm $CO_2$ concentration at $50^{\circ}C$, whereas Au/graphene can detect minimum 2 ppm $CO_2$ concentration at same at $50^{\circ}C$. Moreover, Au NPs catalyst improved the sensitivity of the graphene based $CO_2$ sensors. The responses of pure graphene and Au/graphene are 0.04% and 0.24%, respectively, at $50^{\circ}C$ with 500 ppm $CO_2$ concentration. The optimum working temperature of $CO_2$ sensors is at $75^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.45 no.6
• /
• pp.324-330
• /
• 2008

Activated carbon/$TiO_2$ (AC/$TiO_2$) composites modified with different concentrations of Fe were prepared. The $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine activated carbon. This indicated the blocking of the micropores on the surface of AC, which was further supported by observation via SEM. XRD results showed patterns for the composites and an anatase typed titanium dioxide structure with a small part of rutile in a higher Fe concentration (> 1.0 mol/L). EDX results showed the presence of C and, O, with Ti peaks on the composites of Fe-AC/$TiO_2$ with relatively lower Ti concentration, which may be due to the higher Fe concentration incorporated into the composites. Subsequently, the photocatalytic effects on methylene blue (MB) were investigated. The improved decomposition of MB showed the combined effects of adsorptions and photodegradation. Especially, the composites modified by Fe revealed enhanced photodegradation behaviors of MB.

• Applied Chemistry for Engineering
• /
• v.18 no.2
• /
• pp.136-141
• /
• 2007

The decomposition of chlorinated methanes including $CCl_4$, $CCl_3H$, and $CCl_2H_2$ was carried out using a thermal plasma process and the characteristics of the process were investigated. The thermal equilibrium composition was analyzed with temperature by Fcatsage program. The decomposition rates at various process parameters including the concentration of reactants, flow rate of carrier gas, and quenching rate, were evaluated, where sufficiently high conversion over 92% was achieved. The generation of main products was strongly influenced by the reaction atmosphere; carbon, chlorine, and hydrogen chloride at neutral condition; carbon dioxide, chlorine, and hydrogen chloride at oxidative condition. The decomposition mechanism was speculated considering the results from Factsage and the identification of generated radicals and ionic species. The main decomposition pathways were found to be dissociative electron attachment and oxidative by radicals formed in a plasma state.