Absorption of a volatile organic compound by a jet loop reactor with circulation of a surfactant solution: performance evaluation.

Biofiltration shows high efficiency for the removal of industrial waste gases and reliable operational stability at low investment and operating cost, especially when the VOC concentration is low, such as 100 ppmv (micro LL(-1)) or less. However, it has been reported that the abrupt change in VOC concentrations leads to the failure of the biofilter. Hence, the pretreatment of waste gases is necessary to ensure the stable operation of the biofilter. The objective of this study is to develop a jet loop reactor (JLR) with circulation of a surfactant solution to lower the concentration of VOCs, especially hydrophobic VOCs. Toluene and Tween 81 were used as a model industrial waste gas and a surfactant, respectively. Among several non-ionic surfactants tested, Tween 81 showed the most rapid dissolution of toluene. When a JLR is replaced with fresh Tween 81 solution (0.3% w/v) every hour, it successfully absorbed for 48 h over 90% of the toluene in an inlet gas containing toluene at 1000 ppmv (microL L(-1)) or less. Therefore, JLR with circulation of a surfactant solution is believed to ensure the stable operation of the biofilter even with the unexpected increase in the VOC concentrations.

Distribution of phenanthrene between soil and an aqueous phase in the presence of anionic micelle-like amphiphilic polyurethane particles.

Sorption of micelle-like amphiphilic polyurethane (APU) particles to soil was studied and compared to that of a model anionic surfactant, sodium dodecyl sulfate (SDS). Three types of APU particles with different hydrophobicity were synthesized from urethane acrylate anionomers (UAA) and used in this study. Due to the chemically cross-linked structure, APU exhibited less sorption to the soil than SDS and a greater reduction in the sorption of phenanthrene, a model soil contaminant, to the soil was observed in the presence of APU than SDS even though the solubility of phenanthrene was higher in the presence of SDS than APU. A mathematical model was developed to describe the phenanthrene distribution between soil and an aqueous phase containing APU particles. The sorption of phenanthrene to the test soil could be well described by Linear isotherm. APU sorption to the soil was successfully described by Langmuir and Freundlich isotherms. The partition of phenanthrene between water and APU were successfully explained with a single partition coefficient. The model, which accounts for the limited solubilization of phenanthrene in sorbed APU particles, successfully described the experimental data for the distribution of phenanthrene between the soil and the aqueous phase in the presence of APU.

Fabrication of high quantum yield quantum dot/polymer films by enhancing dispersion of quantum dots using silica particles.

We have fabricated quantum dot (QD)/polymer films of high quantum yield by coating silica particles with quantum dots. When particles were dispersed in tetrahydrofuran, free QD suspension exhibited higher quantum yield than QD-coated silica particles. Scattering is a most likely reason for the drop in quantum yield for the QD-coated silica particles, as supported by results of silica particles with varying morphologies: for example, QD-coated hollow silica particles showed higher quantum yield than filled silica particles, as the hollowness gave rise to reduced scattering. In the QD/polymer films, however, QD-coated filled/hollow silica particles showed significant enhancement in quantum yield (i.e., up to 2.4 times higher than that of free QDs). Confocal microscopy revealed that the enhanced quantum yield likely results from improved dispersion of QD-coated silica particles. In addition, the quantum yield of QD-coated hollow silica particles in films was lower than that of filled particles because of lower structural stability. Introducing silica (either filled or hollow) particles prevents spectral redshift of emission peak when prepared in the form of film, as opposed to QD-only sample. Our findings point to the possibility that QD-coated filled/hollow silica particles exhibit superior stability, quantum efficiency, and color accuracy, which render them potentially useful for the next-generation light-emitting devices and photovoltaics.

Adhesion of nano-sized particles to the surface of bacteria: mechanistic study with the extended DLVO theory.

Due to the increasing production and application of nanoparticles, their release into the environment would be inevitable, which requires a better understanding of their fate in the environment. When considering their toxic behavior or biodegradation as their fate, their adhesion to the cell surface must be the first step to be thoroughly studied. In this study, nano-sized polymeric particles of urethane acrylate with various hydrophobicity and ionic properties were synthesized as model nanoparticles, and their adhesion to Pseudomonas putida strains was monitored. The higher hydrophobicity and positive charge density on the particle surface exhibited the larger adhesion to the bacteria, whereas negative charge density on the particle hindered their adhesion to the bacteria, albeit high hydrophobicity of particle. These observations were successfully explained with the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.

Influence of naphthalene biodegradation on the adhesion of Pseudomonas putida NCIB 9816-4 to a naphthalene-contaminated soil.

In an earlier study, Pseudomonas putida NCIB 9816-4, which was one of the most studied naphthalene-degrading bacteria, showed the preferred adhesion to the naphthalene-contaminated soil when it was in the exponential growth phase. The adhesion was found to take place through a hydrophobic interaction. We postulated that the surface hydrophobicity of P. putida NCIB 9816-4 in the exponential growth phase might be increased during the uptake of naphthalene, which caused the preferred adhesion to the naphthalene-contaminated soil. To verify this postulate, a plasmid-cured strain of P. putida NCIB 9816-4 was obtained in this study and compared with the wild-type for adhesion to the naphthalene-contaminated soil. Only the wild-type in the exponential growth phase showed increased adhesion to naphthalene-contaminated soil. The water contact angles of the two strains were measured in the presence and in the absence of naphthalene as indices of surface hydrophobicity. The water contact angle of the wild-type increased in the presence of naphthalene, whereas that of the cured strain did not change. We conclude that the uptake of naphthalene during naphthalene biodegradation in the exponential growth phase of P. putida NCIB 9816-4 made the cell surface more hydrophobic, resulting in increased adhesion to naphthalene-contaminated soil.

Enhanced production of manganese peroxidase from immobilized Phanerochaete chrysosporium due to the increased autolysis of chlamydospore-like cells.

The autolysis of chlamydospore-like cells in Phanerochaete chrysosporium immobilized in polyurethane foam correlated with the production of manganese peroxidase (MnP). The maximum specific activity of MnP was 1055 U g dry mycelium(-1) in the immobilized culture, compared with 260 U g dry mycelium(-1) in the submerged culture. Scattered mycelial pellets were formed in the immobilized culture in which almost all of the chlamydospore-like cells were subject to autolysis. However, highly crowded pellets were formed in the free culture, in which only the chlamydospore-like cells in the exterior were subject to autolysis. We propose that the enhanced production of MnP in immobilized cultures of P. chrysosporium is due to increased autolysis of the chlamydospore-like cells.

Evaluation of cellulose-binding domain fused to a lipase for the lipase immobilization.

A cellulose-binding domain (CBD) fragment of a cellulase gene of Trichoderma hazianum was fused to a lipase gene of Bacillus stearothermophilus L1 to make a gene cluster for CBD-BSL lipase. The specific activity of CBD-BSL lipase for oil hydrolysis increased by 33% after being immobilized on Avicel (microcrystalline cellulose), whereas those of CBD-BSL lipase and BSL lipase decreased by 16% and 54%, respectively, after being immobilized on silica gel. Although the loss of activity of an enzyme immobilized by adsorption has been reported previously, the loss of activity of the CBD-BSL lipase immobilized on Avicel was less than 3% after 12 h due to the irreversible binding of CBD to Avicel.