Moon-Sun Kim

Removal of paraquat dissolved in a photoreactor with TiO2 immobilized on the glass-tubes of UV lamps.

Experiments were performed to investigate the effects of operating parameters, such as air-inflow rate, UV-light intensity, and film thickness of the photocatalyst, on the photo-decomposition efficiency of paraquat in an immersion-type reactor with TiO2 immobilized by three kinds of methods on the glass tube of UV lamps. As the number of TiO2 coating-time increased from 1 to 4, film thickness on the glass tube by a dip-coating method increased from 355 to 1180 A. The removal efficiency of paraquat using TiO2 prepared by the hydrothermal method was the highest, being 99% in a 12 h operation of 3-type TiO2 immobilized by a sol-gel method and a hydrothermal method, including a commercial product P-25, while that in the absence of TiO2 with only the UV light was the lowest, being 50% in 12 h. The conversion ratios of paraquat at the volumetric flow rates of 5, 10, and 20 mL min(-1) were 46%, 25%, and 17% in 18 h, respectively.

Removal of Cu(II) from aqueous solutions by adsorption process with anatase-type titanium dioxide

The experiment was performed in the reactor with suspended anatase-type titanium dioxide particles. The adsorption amount increased rapidly with an increasing pH value from pH 2 to 5 and remained constant over pH 5. The adsorption amount of Cu(2+) increased with temperature from 15 degrees C to 40 degrees C. The adsorption equilibrium constant (K(ads)) was 0.854 and adsorption isotherm of Cu(2+) adsorption on titanium dioxide was more suitable in Langmuir adsorption isotherm than in Freundlich isotherm. The adsorption rate was rapid with an increasing number of UV lamps of 254 nm.

Photodegradation of acid red 114 dissolved using a photo-Fenton process with TiO2

Abstract A dye acid red 114 (C.I. 23635) was photochemically removed by adding ferric ion (Fe3+), TiO2 particles, and H2O2 in the presence of the UV radiation. The removal rates of the acid red 114 (C.I. 23635) dye were 0.183, 0.210, and 0.233 mg/l/min when the concentrations of Fe3+ were 50, 100, and 130 mg/l. The removal rate of the dye increased from 0.173, through 0.200, 0.210 to 0.260 mg/l/min when the H2O2 concentrations were 10, 50, 100, and 150 mg/l, respectively. The removal rates were 0.200, 0.207, 0.210, 0.273, and 0.293 mg/l/min when the concentrations of TiO2 were 40, 60, 100, 500, and 1000 mg/l, respectively. The removal rate at pH 2.5 was higher than any other; pH 3.5, 5.5, and 8.5 and the photodegradation efficiency increased with the flow rate of air in the range from 1 to 10 l/min. From these results, relationships between the removal rate and the concentration of added Fe3+, H2O2, and TiO2 could be expressed as the following second-order equations, respectively, Rremoval=3×10−6 ×(CFe3+)2+5×10−5 ×(CFe3+)+0.1729; Rremoval=2×10−6 ×(CH2O2)2+2×10−3 ×(CH2O2)+0.1759; and Rremoval=−1×10−7 ×(CTiO2)2+2×10−4×(CTiO2)+0.1867.

Photodegradation of alachlor with the TiO2 film immobilised on the glass tube in aqueous solution

Alachlor photodegradation was performed using TiO(2), which was synthesized by a modified sol-gel method. The thickness of a TiO(2) film immobilised by a 5-time dip-coating was 174 nm and the average diameter of TiO(2) particles was about 10-15 nm in SEM images. The crystal structure of a TiO(2) film calcinated at 300 degrees C for 1 h was observed as a typical anatase type. The stability of a TiO(2) film by a modified sol-gel method was 4% better than TiO(2) by a typical sol-gel method. The removal rate of alachlor with both Fe(3+) and UV radiation in the absence of TiO(2) was 0.28 mg/l/h in 10 h and the removal rate of alachlor with Fe(3+)/UV in the presence of TiO(2) was 0.32 g/l/h, which was higher by 14% than that with Fe(3+)/UV system. TOC concentration during the alachlor degradation with both TiO(2) and UV radiation in the absence of added Fe(3+) decreased from 100%, through 81% and 51%, to 44% with time elapses of 4, 8, and 10 h, respectively, while TOC concentration with both added Fe(3+) and UV radiation in the absence of TiO(2) decreased from 100% to 70% in 10 h.

Removal of paraquat in aqueous suspension of TiO2 in an immersed UV photoreactor

Experiments were performed to investigate the effect of operating parameters on the photodegradation efficiency of paraquat in a TiO2-suspended photoreactor with immersed UV lamps. TiO2 particles were prepared by a hydrothermal method. The removal rate of paraquat in the reactor was 0.54 mg/l/h with only air-sparging. The removal rate in 24 h with both the UV radiation and air-sparging was 50% higher than that with only the UV radiation. Variations of the paraquat concentration at the UV intensities of 4 and 8 W/m2 decreased slowly with time, but that at 12 W/m2 decreased more rapidly. The removal efficiency at the air-sparging flow rate of 1 //min increased as a UV light intensity increased. pH value in the reactor at the UV intensity of 12 W/m2 decreased with time until 12 h and then increased with time over 12 h.

Application of a hybrid system comprising carbon-doped TiO2 film and a ceramic media-packed biofilter for enhanced removal of gaseous styrene.

It is difficult to efficiently remove gaseous styrene using a TiO(2) film-coated photoreactor under UV light. Therefore, we used a hybrid system consisting of a carbon-doped TiO(2) (C-TiO(2)) film and a media-packed biofilter in order to enhance the removal efficiency (RE) of gaseous styrene compared to that of a pure (undoped) TiO(2) photoreactor. The C-TiO(2) was synthesized by a sol-gel combustion method, and its absorption spectrum was stronger that of pure (undoped) TiO(2) in the UV-vis range. The resultant RE of the C-TiO(2) film was 113-200% higher than that of the pure TiO(2) film. The initial RE of the photoreactor for input styrene concentrations of 630 mg m(-3), 420 mg m(-3), and 105 mg m(-3) was 20.6%, 29.8%, and 40.0%, respectively. When the biofilter was added, the RE increased to 93.3%, 97.9%, and 99.0%, respectively. Thus, application of the hybrid system consisting of both a photoreactor coated with a C-TiO(2) film and a biofilter is advantageous in terms of the removal efficiency of gaseous styrene.

Evaluation of photocatalytic activity of carbon-doped TiO2 films under solar irradiation

We proposed a method to obtain carbon-doped TiO2 (C-TiO2) with a higher photocatalytic activity for degradation of toluene. Solar radiation was used as a visible light source for photocatalytic oxidation. An optical fiber reactor (OFR) was used to investigate the photocatalytic oxidation of toluene in air. All C-TiO2 films used as catalysts were synthesized by a modified sol-gel and combustion method using carbon nanoparticles. The performance of the OFR using C-TiO2 was evaluated under various experimental conditions. The effects of solar flux, surface sensitization, inlet concentration of toluene and concentration of carbon nanopowder in C-TiO2 were examined.

Removal of gaseous toluene by using TiO2 film doped of Ru-dye/Pt in a pilot scale photoreactor

The photodegradation efficiency (PE) of gaseous toluene was investigated by using titanium dioxide (TiO2) film doped of ruthenium (Ru)-dye/platinum (Pt) in a 3,600 L pilot reactor. Ru-dye was applied as a sensitizer to enhance PE of toluene in both UV and visible wavelength range since its major peaks are 225 nm, 325 nm, 375 nm, and 525 nm. PE by using Pt/TiO2 was more enhanced since Pt plays a role as an electron trapper in UV light range. The 3.2 μm thickness of TiO2 film was optimized for the highest PE. The highest PE was 75%, 85%, and 90% by TiO2, Pt/TiO2, and Ru-dye/Pt/TiO2 film, respectively.

Effects of molar substitution of AA pendant on poly(MMA-co-GMA) under UV curing

The molar substitution of an acrylic acid (AA) pendant group on a glycidyl methacrylate–methyl methacrylate copolymer was investigated to evaluate its affects on mechanical properties and thermal stability under UV curing. Structural analysis was conducted by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy (1H-NMR) to study the synthetic route of the acrylate copolymer. The mechanical behaviors of AA substituted copolymers were interpreted in terms of both their loss tangent and elongation at the break point, because AA increases the cross-linking density, which is directly proportional to the degree of homopolymerization; this relationship was monitored by 1H-NMR with various molar substitutions. In addition, the optical and mechanical properties of the copolymers were also characterized by the extent of AA molar substitution. The optimal behavior was obtained at a molar substitution of 94.3% (equivalent to an AA/GMA molar ratio of 1.4) and satisfied both the transparency (>89.3%) and elongation (>7.4%) requirements for the complex-shaped coatings.

Effect of Phosphorus on the Corrosion Behavior of Carbon Steel in Sulfuric Acid

Abstract This study examined the influence of phosphorus addition on the corrosion resistance of carbon steel for a flue gas desulfurization (FGD) system using electrochemical methods, such as pote...