Non-uniform filtration velocity of process gas passing through a long bag filter.

Filtration velocity is one of the dominant parameters that determine the pressure drop through a bag filter. Experimental investigation of the air flow pattern around a bag filter inside a bag house is very difficult because of the complexity of the 3-D air flow. For this reason, we numerically investigated flow characteristics along a bag filter in detail. We newly found that the filtration velocity is non-uniform along the axial direction of a long bag filter when the height of the filter is greater than 10 m. The filtration velocity is very small at the bottom of the bag filter but very large at the top. For bag filter lengths of over 10 m, 70% of total inlet flow is filtered in just the top 30% of the long bag filter. This indicates that the top section of the long bag filter could deteriorate faster than the bottom section, making it necessary to develop a new method to avoid the problem. We developed an equation that can help predict the initial pressure drop across long bag filters with different heights, but identical filtration characteristics.

Detoxification of simulated textile wastewater using a membraneless electrochemical reactor with immobilized peroxidase.

Simulated textile wastewater was degraded using a membraneless electrochemical reactor with immobilized peroxidase on the porous Celite. The optimal current density was 10 A m(-2), at which the highest amount of hydrogen (H(2)O(2)) could be generated. The decolorization efficiencies of the simulated wastewater using the electrochemical and electroenzymatic methods were 35% and 92%, respectively. Biodegradability, the ratio of 5-day biochemical oxygen demand to chemical oxygen demand (BOD(5)/COD), was enhanced about 1.88 times when using the electroenzymatic treatment rather than raw wastewater, which could not be achieved by the electrochemical treatment. The toxic unit (TU), calculated using the lethal concentration (LC(50)) of Daphnia magna (D. Magna), of effluent treated by electroenzymatic method was below 1, whereas those of simulated textile wastewater and effluent treated by electrochemical method were 11.4 and 3.9, respectively.

Preparation of a highly sensitive enzyme electrode using gold nanoparticles for measurement of pesticides at the ppt level.

A highly sensitive enzyme electrode was prepared based on gold nanoparticles for measurement of pesticides. Gold nanoparticles of 25-30 nm were synthesized on a glassy carbon electrode by double-pulse technique while the coverage was controlled by applied potential and time. The gold nanoparticles were modified to form a self-assembled monolayer, followed by covalent binding of tyrosinase. The TYR-AuNP-GC electrode was compared with bare GC, AuNP-GC, and modified AuNP-GC and TYR-Au (plate type) electrodes in terms of cyclic voltammetry. The voltammograms well represent the sensitivity of enzymatic oxidation of catechol, substrates for the enzyme activity. The prepared electrode integrated into a continuous flow system and was tested to detect pesticides, such as 2,4-D, atrazine, and ziram. Under the optimized conditions of the flow system, the electrode performed reasonably according to the inhibition mechanism in the concentration range of 0.001-0.5 ng mL(-1). The enhanced performance was attributed to the favored microenvironment for the enzyme activity provided by SAM on gold nanoparticles.

Optimized coverage of gold nanoparticles at tyrosinase electrode for measurement of a pesticide in various water samples.

Gold nanoparticles (AuNPs) were electrodeposited onto a glassy carbon (GC) electrode to increase the sensitivity of the tyrosinase (TYR) electrode. By controlling the applied potential and time, the coverage of AuNPs at the TYR electrode was optimized with respect to the current response. The voltammetric measurements revealed a sensitive enzymatic oxidation and electrochemical reduction of substrate (phenol and catechol). The quantitative relationships between the inhibition percentage and the pesticide concentration in various water samples were measured at the TYR-AuNP-GC electrode, showing an enhanced performance attributed by the use of AuNPs.

Improvement of an enzyme electrode by poly(vinyl alcohol) coating for amperometric measurement of phenol.

A poly(vinyl alcohol) film cross-linked with glutaraldehyde (PVA-GA) was introduced to the surface of a tyrosinase-based carbon paste electrode. The coated PVA-GA film was beneficial in terms of increasing the stability and reproducibility of the enzyme electrode. The electrode showed a sensitive current response to the reduction of the o-quinone, which was the oxidation product of phenol, by the tyrosinase, in the presence of oxygen. The effects of the PVA and PVA-GA coating, the pH, and the GA:PVA ratio on the current response were investigated. The sensitivity of the PVA-GA-Tyr electrode was 130.56microA/mM (1.8microA/microM cm(2)) and the linear range of phenol was 0.5-100microM. At a higher concentration of phenol (>100microM), the current response showed the Michaelis-Menten behavior. Using the PVA-GA-Tyr electrode, a two-electrode system was tested as a prototype sensor for portable applications.

Electroenzymatic degradation of azo dye using an immobilized peroxidase enzyme.

Azo dyes are largely resistant to biodegradation and persist in conventional wastewater treatment processes. Combining enzymatic catalysis and the electrochemical generation of hydrogen peroxide (H2O2), an electroenzymatic process was developed, which is a potential alternative to traditional processes. In this study, an electroenzymatic method that uses an immobilized horseradish peroxidase enzyme (HRP), was investigated to degrade orange II (azo dye) within a two-compartment packed-bed flow reactor. To evaluate the electroenzymatic degradation of orange II, electrolytic experiments were carried out with 0.42 U/mL HRP at -0.5 V. It was found that removal of orange II was partly due to its adsorption to the graphite felt. The overall application of the electroenzymatic led to a greater degradation rate than the use of electrolysis alone. Also the by-products formed were found to consist primarily of an aromatic amine, sulfanilic acid, and unknown compounds.