Hua-Wei Chen

Mineralization of reactive Black 5 in aqueous solution by ozone/H2O2 in the presence of a magnetic catalyst

Particles are often too small to be separated from a reaction system and recycled, especially in wastewater treatment via a catalytic ozonation process. Thus, the objective of this study was to prepare a magnetic catalyst (SiO(2)/Fe(3)O(4)) that can be recycled by using an external magnetic field. The effects of the characteristics of the magnetic catalyst, pH values, catalyst dosage, and initial concentration of Reactive Black 5 (RB5) on mineralization efficiency of the magnetic catalyst/H(2)O(2)/O(3) process were also investigated. The mineralization efficiency of RB5 under various conditions followed the sequence: SiO(2)/Fe(3)O(4)/H(2)O(2)/O(3)>SiO(2)/Fe(3)O(4)/O(3)>Fe(3)O(4)/O(3) approximately H(2)O(2)/O(3)>O(3)>SiO(2)/Fe(3)O(4)/H(2)O(2). Given the results of our reuse and recovery experiments, the magnetic catalyst shows considerable promise for use in water treatment.

Decomposition of Benzene and Toluene in Air Streams in Fixed-Film Photoreactors Coated with TiO2 Catalyst

Abstract The decomposition of benzene and toluene in air streams by UV/TiO2 process was studied in different annular photoreactors under various operating conditions. The shells of reactors used in this research are made of stainless steel, Pyrex glass, or titanium. The TiO2 film was coated to the inner surface of the reactors by either rotating coating or sol-gel techniques. The TiO2 films coated by sol-gel technique were found to be smoother and more uniform than those coated by rotating coating. However, experimental results indicated that the photocatalysis of benzene or toluene in a glass reactor with rotating-coated TiO2 film delivered higher decompositions in air streams than that with sol-gel coated reactors. Benzene and toluene were decomposed more effectively in a coated glass reactor than in a coated stainless steel reactor under the same operating conditions. The presence of water vapor in air-stream plays an important role in the decomposition of benzene and toluene, and a relative humidity of ∼5–6% was found to be adequate. The presence of excessive amounts of humidity retarded the decomposition to certain extents possibly results from the competitive adsorption of water molecules on the active sites of TiO2.

The effect of surfactants on the ozonation of o‐cresol in aqueous solutions in a rotating packed contactor

Steady‐state dissolved ozone concentrations were maintained relatively constant for experiments on ozone dissolution conducted in the presence of various amounts of sodium dodecyl sulphate (SDS) and Triton X‐100 (TX‐100), an anionic surfactant and a nonionic surfactant, respectively. Ozonation in a rotating packed contactor has been shown to be feasible for achieving nearly complete decomposition of o‐cresol within about 10 minutes of reaction time for most experiments conducted. The temporal decomposition behaviour of o‐cresol in aqueous solution by ozonation was described by a two‐step pseudo‐first‐order reaction kinetics. Even though the presence of SDS and TX‐100 slightly affected the decomposition rate constant of o‐cresol by ozonation in the rotating packed contactor, the mineralization of total organic carbon was apparently reduced with the addition of SDS and TX‐100.

Effect of sodium dodecyl sulfate (SDS) on bubble characteristics and ozone transfer in a bubble column

Abstract The rising of ozone‐containing bubbles in a bubble column was examined by a high‐speed micro video camera. The shape of the bubbles shifted from spherical to ellipsoidal during their rise along the column. The experimental observation indicated that the average diameter at the X‐axis of the bubbles was markedly increased after the bubbles left the diffuser because the gas pressure inside the bubbles was not balanced with the surrounding water pressure. However, the shape of bubbles was kept spherical along the column during an experiment conducted in the presence of sodium dodecyl sulfate (SDS), a commonly used surfactant. In pure water, the intrinsic interfacial areas for the bubble column were determined to be in the range of 2.958 to 8.607 m–1 for experiments conducted with the gas flow rate from 3.25 × 10–6 to 1.16 x 10‐5 m3/s, and the intrinsic mass transfer coefficient of ozone, kL , was found to be 0.0004 m/s at 25°C and 1 atm. The determined overall and the specific gas‐liquid contact area were notably increased from 0.0059 m2 and 2.958 m–1 to 0.0197 m2 and 8.964 m–1, respectively, with the presence of 0.0346 mM of SDS in the aqueous solution.

Removal of fluoride from aqueous solution by aluminum-loaded Duolite C-467 resin

Our research interests were in the effects of pH, temperature, flow rate, and amount of resin on the kinetic behavior of fluoride removal using an aluminum-loaded synthetic resin, Duolite C-467, in batch reactors and fixed-bed adsorption columns, in order to obtain more practical design and operating data for a particular column. The results indicated that the removal efficiency was influenced significantly by solution pH and the optimum pH was found to be in the range 5.0–7.0. The removal of fluoride by the resin was interfered with by the presence of sulfate ions because of the competition for surface sites and neutralization of surface charge of resin. The Bed-Depth-Service-Time model can adequately describe the adsorption behavior of fluoride by aluminum-loaded Duolite C-467 resin in a fixed-bed column, also indicating that the adsorption rate of fluoride ion is mainly determined by the surface reaction step.

Ozone Transfer and Decomposition of Isopropyl Alcohol by H2O2/Ozone Process in a Rotating Packed Contactor

Abstract Ozone transfer and decomposition of isopropyl alcohol in aqueous solution by H2O2/O3 process in a rotating packed contactor was studied under various operational conditions. Decomposition of isopropyl alcohol by H2O2/O3 process in a rotating packed contactor has been shown to be feasible and can be described with a simplified pseudo-first order kinetic model. Both the overall ozone transfer coefficient and the decomposition rate of isopropyl alcohol by H2O2/O3 process in the rotating packed contactor were enhanced with the increase of rotor speed. The decomposition rate was greatly affected by the rotor speed for experiments conducted at lower gas/liquid flow rate ratio. The decomposition of isopropyl alcohol was favored to occur in neutral and alkaline solutions; however, the decomposition rate of isopropyl alcohol for experiment conducted at pH 11 was found to be hindered. The decomposition of isopropyl alcohol was accelerated with increasing H2O2/O3 molar ratio. However, for experiments conducted in neutral and alkaline solutions, excessive additions of H2O2 might serve as scavenger for OH• free radicals to inhibit the decomposition of isopropyl alcohol.