• 한국대기환경학회지
• /
• 제18권3호
• /
• pp.223-230
• /
• 2002

Titania photocatalytic oxidation reactors were studied to investigate degradation efficiencies of hydrocarbons. In general, it is well known phenomena that thin layered titania oxidizes most of hydrocarbons to carbon dioxide and water under UV light. In this study, degradation efficiencies were measured due to changes in reactor structures, UV sources, the number of titania coatings, and various hydrocarbon chemicals. It was proven that gas degradation efficiencies are related to such factors as UV transmittance of coating substance, collision area of surface, and gas flow rate. For packing type annular reactor, about 98% degradation efficiency was achieved for achieved for propylene of 500 ppm level at a flow rate of 100 ml/min. Several gases were also tested for double-coated titania thin film under the condition of continuous flow of 100 ml/min and 365 nm UV source. It was shown that degradation efficiencies were decreasing in the order: $C_3$ $H_{6}$, n-C$_4$ $H_{10}$, $C_2$ $H_4$, $C_2$ $H_2$, $C_{6}$ $H_{6}$ and $C_2$ $H_{6}$./. 6/./.

• Environmental Engineering Research
• /
• 제18권1호
• /
• pp.21-28
• /
• 2013

In this study, the applicability of visible light-emitting-diodes (LEDs) to the photocatalytic degradation of indoor-level trichloroethylene (TCE) and perchloroethylene (PCE) over N-doped $TiO_2$ (N-$TiO_2$) was examined under a range of operational conditions. The N-$TiO_2$ photocatalyst was calcined at $650^{\circ}C$ (labeled N-650) showed the lowest degradation efficiencies for TCE and PCE, while the N-$TiO_2$ photocatalysts calcined at $350^{\circ}C$, $450^{\circ}C$, and $550^{\circ}C$ (labeled as N-350, N-450, and N-550, respectively) exhibited similar or slightly different degradation efficiencies to those of TCE and PCE. These results were supported by the X-ray diffraction patterns of N-350, N-450, N-550, and N-650. The respective average degradation efficiencies for TCE and PCE were 96% and 77% for the 8-W lamp/N-$TiO_2$ system, 32% and 20% for the violet LED/N-$TiO_2$ system, and ~0% and 4% for the blue LED/N-$TiO_2$ system. However, the normalized photocatalytic degradation efficiencies for TCE and PCE for the violet LED-irradiated N-$TiO_2$ system were higher than those from the 8-W fluorescent daylight lamp-irradiated N-$TiO_2$ system. Although the difference was not substantial, the degradation efficiencies exhibited a decreasing trend with increasing input concentrations. The degradation efficiencies for TCE and PCE decreased with increasing air flow rates. In general, the degradation efficiencies for both target compounds decreased as relative humidity increased. Consequently, it was indicated that violet LEDs can be utilized as energy-efficient light sources for the photocatalytic degradation of TCE and PCE, if operational conditions of N-$TiO_2$ photocatalytic system are optimized.

• 공업화학
• /
• 제34권6호
• /
• pp.649-659
• /
• 2023

This study was initiated to evaluate the phosphorus (P) removal and diesel oil degradation by bacteria isolated from industrial wastewater. The bacteria isolated were identified as Bacillus sp. The P removal efficiencies by Bacillus sp. were 99% at the initial 20 mg/L P concentration. The diesel degradation efficiencies by Bacillus sp. were 86.4% at an initial 1% diesel concentration. Lipophilicity by bacteria was the highest in the log phase, whereas it was the lowest in the death phase. As the diesel was used as a carbon source, P removal efficiencies by Bacillus sp. were 68%. When glucose, acetate, and a mixture of glucose and acetate as second carbon sources were added, the diesel degradation efficiencies were 69.22%, 65.46%, and 51.46%, respectively. The diesel degradation efficiency was higher in the individual additions of glucose or acetate than in the mixture of glucose and acetate. When P concentration increased from 20 mg/L to 30 mg/L, the diesel degradation efficiency was increased by 7% from 65% to 72%, whereas when P concentration was increased from 30 mg/L to 40 mg/L, there was no increase in diesel degradation. One of the five proteins identified by proteome analysis in the 0.5% diesel-treated samples may be involved in alkane degradation and is known as the cytochrome P450 system. Also, two of the sixteen proteins identified in the 1.5% diesel-treated samples may be implicated in the fatty acid transport system and alcohol dehydrogenation.

• 한국환경과학회지
• /
• 제17권11호
• /
• pp.1195-1201
• /
• 2008

Enhancing with non-metallic elemental nitrogen(N) is one of several methods that have been proposed to modify the electronic properties of bulk titanium dioxide($TiO_2$), in order to make $TiO_2$ effective under visible-light irradiation. Accordingly, current study evaluated the feasibility of applying visible-light-induced $TiO_2$ enhanced with N element to cleanse aromatic compounds, focusing on xylene isomers at indoor air quality(IAQ) levels. The N-enhanced $TiO_2$ was prepared by applying two popular processes, and they were coated by applying two well-known methods. For three o-, m-, and p-xylene, the two coating methods exhibited different photocatalytic oxidation(PCO) efficiencies. Similarly, the two N-doping processes showed different PCO efficiencies. For all three stream flow rates(SFRs), the degradation efficiencies were similar between o-xylene and m,p-xylene. The degradation efficiencies of all target compounds increased as the SFR decreased. The degradation efficiencies determined via a PCO system with N-enhanced visible-light induced $TiO_2$ was somewhat lower than that with ultraviolet(UV)-light induced unmodified $TiO_2$, which was reported by previous studies. Nevertheless, it is noteworthy that PCO efficiencies increased up to 94% for o-xylene and 97% for the m,p-xylene under lower SFR(0.5 L $min^{-1}$). Consequently, it is suggested that with appropriate SFR conditions, the visible-light-assisted photocatalytic systems could also become important tools for improving IAQ.

• 산업기술연구
• /
• 제21권B호
• /
• pp.21-26
• /
• 2001

In this study, the effects of crystalinity, composition and particle size of $TiO_2$ catalysts on the degradations of humic acid in aqueous solution was assessed using the commercially avaliable $TiO_2$ particles. Photocatalytic oxidations of humic acid (HA, Aldrich Co.) solution were carried out in case of adding different types of $TiO_2$ catalysts and their decomposition efficiencies were analyzed with respect to pH, DOC and UV absorbances values for the HA solutions and compared one another. The experimental results showed that $TiO_2$ particles(Degussa P-25) mixed with anataze and rutile gave the highest degradation efficiencies, respectively and much lower degradation efficiency in $TiO_2$ paticles of rutile only type. In comparing among ST series of anataze types, it was observed that the degradation efficiencies generally were increased with increasing $TiO_2$ contents and surface area of the particles. Higher degradation efficiency of HA was also found in zeolite type(D-TZ) of $TiO_2$ paticles compared with hydroxyapatite type (D-TH) of $TiO_2$ particles.

• 상하수도학회지
• /
• 제25권4호
• /
• pp.463-469
• /
• 2011

The degradation of 4-chlorophenol by various AOPs(Advanced Oxidation Processes) including the Fenton and the photo-Fenton process has been examined. In sole Fe, UV or $H_2O_2$ process without combination, low removal efficiencies have been achieved. But the photo-Fenton process showed higher removal efficiency for degradation of 4-chlorophenol than those of other AOPs including the Fenton process. Generally more hydrogen peroxide was required to achieve higher removal efficiencies of 4-CP at constant dosage of $FeSO_4$ in both of the Fenton and the photo-Fenton processes. Based on the results, The photo-Fenton process is proposed to be the most efficient alternative for degradation of 4-chlorophenol among the processes studied in this research.

• Environmental Engineering Research
• /
• 제16권2호
• /
• pp.91-96
• /
• 2011

Limited information is available on the degradation of volatile hydrocarbons determined via the use of plate-inserted photocatalytic reactors. This has led to the evaluation of surface areas of cylindrical continuous-flow photocatalytic reactors for the degradation of three selected aromatic hydrocarbons. Three types of reactors were prepared: a double cylinder-type, a single cylindrical-type without plates and a single cylindrical-type with inserted glass tubes. According to diffuse reflectance, FTIR and X-ray diffraction (XRD) spectroscopy, the surface characteristics of a coated photocatalyst were very similar to those of raw $TiO_2$, thereby suggesting that the coated photocatalyst exhibited the same photocatalytic activity as the raw $TiO_2$. The photocatalytic degradation efficiencies were significantly or slightly higher for the single cylinder-type reactor than for the double cylinder-type reactor which had a greater catalytic surface area. However, for all target compounds, the degradation efficiencies increased gradually when the number of plates was increased. Accordingly, it was suggested that the surface area being enhanced for the plate-inserted reactor would elevate the photocatalytic degradation efficiency effectively. In addition, this study confirmed that both initial concentrations of target compounds and flow rates were important parameters for the photocatalytic removal mechanism of these plate-inserted photocatalytic reactors.

• 산업기술연구
• /
• 제21권A호
• /
• pp.273-278
• /
• 2001

In this study, we prepared nano-sized $TiO_2$ particles for various process variables by the diffusion flame reactor and we collected $TiO_2$ particles by thermophoresis. It is found that the size of $TiO_2$ particles increases, as the flame temperature or the inlet $TiCl_4$ concentration increase or the total gas flow rate decreases. We investigated the photo-degradation of phenol wish the prepared $TiO_2$ particles. We found the optimum amounts of $TiO_2$ photocatalysts for our experimental apparatus and investigated the photo-degradation efficiencies of phenol, changing the process variables such as size of $TiO_2$ photocatlysts, phase ratio of rutile/anatase, concentration of phenol, input ratio of $O_2$. Degradation efficiencies of phenol were almost 95% in 15 minutes for the standard conditions of our experiments.

• Environmental Engineering Research
• /
• 제24권2호
• /
• pp.318-323
• /
• 2019

Paper focuses on comparison between two different orifice plate configurations (plate number 1 and plate number 2) used as cavitating device in the hydrodynamic cavitation reactor for improving pollutant removal efficiencies. Effect of four different parameters such as hydraulic characteristics (in terms of range of flow rates, orifice velocities, cavitation number at different inlet pressures); cavitation number (in range of 5.76-0.35 for plate number 1 and 1.20-0.35 for plate number 2); inlet pressure (2-8 bars) and reaction time (0 to 60 min) in terms of chemical oxygen demand (COD) removal and chlorpyrifos degradation has been studied and compared. Optimum inlet pressure of 5 bars exists for degradation of pollutants for both the plates. It is found that geometry of orifice plate plays important role in removal efficiencies of pollutant. Results obtained confirmed that orifice plate 1 with configuration of 1.5 mm 17 holes; cavitational number of 1.54 performed better with around 60% COD and 98% chlorpyrifos removal as compared to orifice plate 2 having configuration of 2 mm single hole; cavitational number of 0.53 with 40% COD and 96% chlorpyrifos in 2 h duration time.

• 산업기술연구
• /
• 제22권B호
• /
• pp.117-124
• /
• 2002

We prepared the nano-sized $TiO_2$ particles by the diffusion flame reactor and investigated the effects of several process variables on the generation and transport properties of $TiO_2$ particle. As the length from the tip of diffusion flame reactor increases, the size of $TiO_2$ particle increases by the coagulation between particles. The structure of $TiO_2$ particles prepared is almost found to be anatase. It was found that the $TiO_2$ particle size depends more largely on the change of reactor temperature than on the change of inlet $TiCl_4$ concentration. By the photo-degradation experiment of phenol and toluene with the prepared $TiO_2$ particles, we found that the photo-degradation efficiencies of phenol and toluene change, depending on the process variables such as size of $TiO_2$ photocatlysts, concentration of phenol or toluene. Degradation efficiencies of phenol and toluene was above 90% in our experiments in 60 minutes.