Determination of the Henry's law constants of low-volatility compounds via the measured air-phase transfer coefficients.

Accurate Henry's law constants (H) are unavailable for the majority of organic pollutants, especially those having a low volatility. A novel kinetics-based experimental method is introduced to determine H for a wide range of low-H compounds. The method consists of measuring independently the water-to-air transfer coefficient (KL) and the associated air-phase transfer coefficient (kG) of a low-H chemical (solute) in water when KL ≅ kGH prevails according to the two-film theory. The kG for a solute is obtained via a developed gas-dynamic equation that relates kG to the solute molecular weight and the solute-vapor escaping efficiency (ß) through a boundary air layer. The value of ß is only a function of the in situ air turbulence level, independent of the chemical species. Thus, the required ß for solutes can be estimated from the evaporative rates of pure volatile liquids under the same ambient setting. By relating the estimated kG with the measured KL of a low-H solute, the solute H is established. The H values of 45 low-H chemicals, including many complex pesticides, in the range of ∼10-7 to ∼10-3 have thus been determined. The accountability of the method is underscored by the consistency of the measured and credible literature H values for a number of the low-H compounds studied.

Immobilization of fungal laccase onto a nonionic surfactant-modified clay material: application to PAH degradation.

Nonionic surfactant-modified clay is a useful absorbent material that effectively removes hydrophobic organic compounds from soil/groundwater. We developed a novel material by applying an immobilized fungal laccase onto nonionic surfactant-modified clay. Low-water-solubility polycyclic aromatic hydrocarbons (PAHs) (naphthalene/phenanthrene) were degraded in the presence of this bioactive material. PAH degradation by free laccase was higher than degradation by immobilized laccase when the surfactant concentration was allowed to form micelles. PAH degradation by immobilized laccase on TX-100-modified clay was higher than on Brij35-modified clay. Strong laccase degradation of PAH can be maintained by adding surfactant monomers or micelles. The physical adsorption of nonionic surfactants onto clay plays an important role in PAH degradation by laccase, which can be explained by the structure and molecular interactions of the surfactant with the clay and enzyme. A system where laccase is immobilized onto TX-100-monomer-modified clay is a good candidate bioactive material for in situ PAHs bioremediation.

A versatile chitosan/ZnO nanocomposite with enhanced antimicrobial properties.

Porous chitosan membrane was fabricated by casting method using silica particles. Simultaneously nano ZnO was synthesized by green-synthesis method using tung ting oolong tea extract. Chitosan membrane was combined with nano ZnO in order to increase its antimicrobial activity. Through observations obtained from various techniques such as XRD, SEM, FT-IR, UV-visible and fluorescence emission analyses, chitosan was seen to be able to incorporate nano ZnO in the nanocomposite membrane. A blue shift (from 360 to 335 nm) was observed in the UV-visible spectrum of nanocomposite and fluorescence emission intensity of nanocomposite was considerably lower than that of nano ZnO. Gram negative organism Klebsiella planticola (MTCC2727) and Gram positive organism Bacillus substilis (MTCC3053) were used to test the antibacterial and antifouling activities of newly synthesized nanocomposite chitosan/ZnO membrane. The nanocomposite chitosan/ZnO membrane promisingly inhibited the bacterial growth when compared with as-synthesized chitosan. Gram negative K. planticola (MTCC2727) was comparatively more susceptible for inhibition than that of Gram positive Bacillus substilis (MTCC3053). In conclusion, nanocomposite obtained in this study showed enhanced antibacterial and antifouling activities. We believed that the enhanced physical properties of nanocomposite achieved by incorporating nano ZnO in the chitosan matrix could be beneficial in various applications.

Effects of porogen and cross-linking agents on improved properties of silica-supported macroporous chitosan membranes for enzyme immobilization.

A series of silica-supported macroporous chitosan membranes (CM15, CM20, and CM25) was prepared by varying the ratio of 70-230-µm-sized silica particles. These synthesized membranes were further cross-linked using different cross-linking agents for covalent immobilization of biological macromolecules especially enzymes and in this study, Bovine serum albumin and laccase. Effects of silica particle and cross-linking agents on their flow rates, surface properties, and chemical and biological properties were explored. Pore size of as-synthesized membranes was 0.1192, 0.1268, and 0.1623 µm, respectively, for CM15, CM20, and CM25. The effect of various parameters such as temperature and pH on the relative activity of both free and immobilized enzymes was studied in details. The relative enzyme activity upon immobilization was greatly enhanced several folds of its original activity. The stability of enzymes over a range of temperature and pH was significantly improved by immobilization. The optimum temperature and pH were determined to be 50 °C and pH 3, respectively, for both the free and the immobilized enzymes. The immobilized enzyme possessed good operational stability and reusability properties that support its potentiality for practical applications. Among three membranes, CM25 is confirmed to be efficient candidate due to its improved characteristics.

Development of silica gel-supported modified macroporous chitosan membranes for enzyme immobilization and their characterization analyses.

The present work was aimed at developing stability enhanced silica gel-supported macroporous chitosan membrane for immobilization of enzymes. The membrane was surface modified using various cross-linking agents for covalent immobilization of enzyme Bovine serum albumin. The results of FT-IR, UV-vis, and SEM analyses revealed the effect of cross-linking agents and confirmed the formation of modified membranes. The presence of silica gel as a support could provide a large surface area, and therefore, the enzyme could be immobilized only on the surface, and thus minimized the diffusion limitation problem. The resultant enzyme immobilized membranes were also characterized based on their activity retention, immobilization efficiency, and stability aspects. The immobilization process increased the activity of immobilized enzyme even higher than that of total (actual) activity of native enzyme. Thus, the obtained macroporous chitosan membranes in this study could act as a versatile host for various guest molecules.

Synthesis of ZnO/Zn nano photocatalyst using modified polysaccharides for photodegradation of dyes.

A complete set of experiments in two aspects of studies combining the various factors affecting both the preparation and photocatalytic activity of ZnO/Zn nanocomposite obtained using corn starch and cellulose (native and modified) as chelating agents for the photodegradation of methylene blue, and congo red was carried out and discussed. The resulting ZnO/Zn nanoparticles obtained using modified polysaccharides exhibited super catalytic capability. The ZnO/Zn nanoparticles possessed favored surface area (11.8443-15.7100m(2)/g) and pore size (12.3473-13.7453nm). The photocatalytic degradation of nano ZnO/Zn was directly proportional to the surface area of nano ZnO/Zn. Regardless of the dye pollutants, nano ZnO/Zn obtained using modified corn starch showed enhanced catalytic activity than that of cellulose and methylene blue had comparatively faster degradation rate. Our findings shed light on the optimization of both preparation conditions of photocatalysts and their photocatalytic experimental conditions.

Investigation of preparation conditions and photocatalytic efficiency of nano ZnO using different polysaccharides.

The development of a complete set of extensive studies combining both the preparation factors of catalysts and photocatalytic experimental factors for the photodegradation of methylene blue, crystal violet, and Congo red using effective nano zinc oxide (ZnO) obtained from polysaccharides (chitosans, corn starch, and sodium alginate) as chelating agents was the main objective of this study. The influence of nature of polysaccharides, ratio of reactants, calcination temperatures during preparation process, and effects of photocatalytic experimental conditions on photodegradation was investigated. Corn starch and sodium alginate were found to be effective chelating agents and optimum preparation parameters were set as 3:3 % ratio of reactants and 450 °C calcination temperature to prepare nano ZnO with good photocatalytic activity. The order of organic dyes based on their photodegradation rates was arranged as crystal violet > methylene blue > Congo red. Our findings shed light on the optimization of both preparation conditions of photocatalysts and photocatalytic experimental conditions.

Preparation and Morphology Studies of Nano Zinc Oxide Obtained Using Native and Modified Chitosans.

Nano zinc oxide (ZnO) with moderate surface area and high pore volume were prepared using a facile preparation method. Chitosan was utilized as both chelating and structure directing agent. The application of chitosans in this study suggested that even biowastes can be served in a productive manner economically. The surface modification of chitosan was carried out in order to increase the interaction between chitosan and zinc ions. The effect of sodium chloroacetate and isopropyl alcohol on the surface modification process was also explored. FT-IR (Fourier transform-infrared spectrometer) and TGA (Thermogravimetric analyses) analyses revealed that modified chitosans are more stable than those of unmodified chitosan. Among surface modified chitosans, CMC1 (1.5 M sodium chloroacetate and 75% isopropyl alcohol) showed enhanced surface properties. Freundlich adsorption isotherms as preliminary studies confirmed that modified chitosan showed enhanced interaction with zinc ions. The interaction of zinc salt with chitosans produced a zinc-chitosan polymer. This finally cleaved upon calcination to produce nano ZnO. The effects of different calcination temperatures indicated that 450 °C is the optimum calcination temperature to produce the nano ZnO with favored surface area (15.45 m²/g) and pore size (221.40 nm). SEM (Scanning electron microscope) and TEM (Transmission electron microscope) of ZnO indicated that uniform particle and shape distributions were obtained at low calcination temperature (450 °C).

Effects of humic acid and suspended soils on adsorption and photo-degradation of microcystin-LR onto samples from Taiwan reservoirs and rivers.

This article covers the adsorption capacity of microcystin-LR (MC-LR) onto natural organic matter (NOM) or suspended solids of water samples from reservoirs (Emerald and Jade reservoirs) and rivers (Dongshan, Erhjen and Wukai rivers) in Taiwan to determine the fate, transport behavior and photo-degradation of microcystins in natural water systems. Langmuir adsorption and photo-degradation studies were carried out and the capability of samples for MC-LR adsorption was confirmed. Among these, samples collected from reservoir showed enhanced MC-LR adsorption than that of river samples and the greater adsorption behavior was always favored by larger content of organic matter and suspended particles in the system. It is obvious from the experimental results that the adsorption of MC-LR was influenced by suspended particles (turbidity), humic acid (HA), organic matter content and other pollutants. The effective photo-degradation of MC-LR was achieved using higher energy, lower wavelength (254 nm) UV light within 60 min. The presence of humic acid and turbidity affected the photo-degradation process. These data provide important information that may be applied to management strategies for improvement of water quality in reservoirs and rivers and other water bodies in Taiwan.

Adsorption and photodegradation of microcystin-LR onto sediments collected from reservoirs and rivers in Taiwan: a laboratory study to investigate the fate, transfer, and degradation of microcystin-LR.

BACKGROUND, AIM, AND SCOPE: This study demonstrated the adsorption capacity of microcystin-LR (MC-LR) onto sediment samples collected from different reservoirs (Emerald and Jade reservoirs) and rivers (Dongshan, Erhjen, and Wukai rivers) in Taiwan to investigate the fate, transport behavior, and photodegradation of MC-LR. MAIN FEATURES: Langmuir adsorption and photodegradation studies were carried out in the laboratory and tested the capability of sediments for MC-LR adsorption. These data suggested that sediments play a crucial role in microcystins degradation in aquatic systems. RESULTS AND DISCUSSION: The results of batch experiments revealed that the adsorption of MC-LR varied significantly with texture, pH, and organic matter content of sediments. Silty and clay textures of the samples were associated with larger content of organic matter, and they displayed the enhanced MC-LR adsorption. Low pH sediment showed increased adsorption of MC-LR. The effective photodegradation of MC-LR (1.6 µg/mL) was achieved within 60 min under 254 nm light irradiation. CONCLUSION: A comparative study of adsorption capacity of all sediment samples was carried out and discussed with respect to different aspects. Among all, sediments collected from Jade reservoir showed enhanced MC-LR adsorption (11.86 µg/g) due to favored textural properties (BET surface area = 20.24 m2/g and pore volume = 80.70 nm). PERSPECTIVES: These data provide important information that may be applied to management strategies for improvement of water quality in reservoirs and rivers and other water bodies in Taiwan.

Field evaluation of measuring indoor noise exposure in workplace with task-based active RFID technology.

This paper describes the research using RFEMS (Radio Frequency Identification Exposure Monitoring System), which is designed by applying the task-based active RFID (radio frequency identification) technology, to measure the indoor noise exposure dose in a workplace. The RFEMS and sound level meter are mounted on the vests of eight workers to carry out on-site field test by monitoring the time activity pattern (TAP), and the noise dose level exposed by the workers. The data are recorded and instantaneously transmitted to a computer to be saved in the server and later compared to those obtained using the standard method. The results that have a 0.909 correlation coefficient (R(2)), and 1.64% average measure error confirm the accuracy of using RFEMS for monitoring TAP. Additionally, the combined use of RFEMS and sound level meter leads to the development of a semi noise dosimetry (SND), a real-time electronic indirect noise dosimetry (REIND), and an equivalent electronic recording indirect noise dosimetry (EEIND). The results obtained using these three devices are well correlated with the results monitored by using a PND (personal noise dosimetry) with correlation coefficients (R(2)) of 0.915, 0.779 and 0.873, respectively. The errors of noise dose expressed in TWA (time weight average) for these three methods are 0.81, 1.57 and 1.23 dBA, respectively; they are well within the general errors of the average dosimetries. These observations indicate that the RFEMS developed in this research is applicable for conducting task-based measurements of indoor noise. It uses a relatively inexpensive sound level meter to measure the noise exposure doses that are comparable to those obtained with a standard dosimetry in addition to monitoring the worker's time activity pattern. The findings will assist in studying the source of long-term noise exposed by workers, and hence this devise is a valuable tool for tracing and monitoring long-term noise exposure with reduced manpower requirements.

Effects of PAH biodegradation in the presence of non-ionic surfactants on a bacterial community and its exoenzymatic activity.

The influence of two non-ionic surfactants (TX-100 and Brij 35) on a bacterial community and its exoenzymatic activity during polycyclic aromatic hydrocarbon (naphthalene, phenanthrene and pyrene) biodegradation was evaluated in this study. The result indicated the addition of the non-ionic surfactants altered the profiles of the microbial populations and produced exoenzymes. Fluorescence in situ hybridization found that, as PAH biodegradation progressed in the presence of non-ionic surfactant, the proportion of Bacteria presents increased significantly from the range 54.79%-57.00% to 64.17%-73.4% and there was parallel decrease in Archaea. The trends in five phyla/subclass of Bacteria, namely alpha -, beta -, or gamma -Proteobacteria, HGC bacteria and LGC bacteria, were influenced significantly by the addition of Brij 35 as either monomers or micelles. A change was ascribed to different cohesive energy density (CED) value between the PAH and surfactant. The percentage of genera Pseudomonas 4.76%-12.67%, which included two signals, namely most true Pseudomonas spp. and Pseudomonas aeruginosa, were dominant during biodegradation. For exoenzymaztic activities, trends were identified by principle component analysis of the API ZYM enzymatic activity dataset. The additions of non-ionic surfactant were identified strong activities of three esterase (esterase, esterase lipase and lipase), alpha -glucosidase, beta -glucosidase, leucine arylamidase and acid phosphatase during PAH biodegradation. These enzymes are selected as possible organic pollutant indicators when the in situ bioremediation was monitored in the presence of non-ionic surfactant additives.

Time location analysis for exposure assessment studies of indoor workers based on active RFID technology.

In this article, we describe the development of a radio frequency identification exposure monitoring system (RFEMS) suitable for tracking and identifying workers' locations in indoor workplaces. Five workers in southern Taiwan wore the RFEMS integrated into their equipment vests. Location and exposure data were transferred to data analysis software for visualization and tabular analysis in real-time. Data were grouped into seven task activity location categories to determine the time spent and percentage reception in each location. The RFEMS could also synchronously indicate the surrounding conditions using various sensors. Additional experiments were focused on locating of boundaries and determining the instrument stability, power sustainability, and reception efficiency in typical environments. The RFEMS instruments provided adequate range for locating (typically ca. 6-45 m in each zone), allowing us to locate subjects within distinct microenvironments and to distinguish between the activities of a variety of workers, the average time activity pattern (TAP) recording deviation for both human observations and RFEMS was ca. 0.21-1.57%. Power consumption experiments revealed that the system could be sustained for more than 124 h. A pilot field test indicated that the RFEMS offers a new level of accuracy for direct quantification of time activity patterns in exposure assessments of indoor workers over long periods of time.

Biosorption of Zn(II) on the different Ca-alginate beads from aqueous solution.

The performance of a new biosorbent system, consisting of a fungal biomass immobilized within an orange peel cellulose absorbent matrix, for the removal of Zn(2+) heavy metal ions from an aqueous solution was tested. The amount of Zn(II) ion sorption by the beads was as follows; orange peel cellulose with Phanerochaete chrysosporium immobilized Ca-alginate beads (OPCFCA) (168.61 mg/g) > orange peel cellulose immobilized Ca-alginate beads (OPCCA) (147.06 mg/g) > P. chrysosporium (F) (125.0 mg/g) > orange peel cellulose (OPC) (108.70 mg/g) > plain Ca-alginate bead (PCA) (98.26 mg/g). The Zn(2+) concentration was 100 to 1000 mg/L. The widely used Langmuir and Freundlich isotherm models were utilized to describe the biosorption equilibrium process. The isotherm parameters were estimated using linear and non-linear regression analysis. The Box-Behnken model was found to be in close agreement with the experimental values, as indicated by the correlation coefficient value of 0.9999.

Selective adsorption and partitioning of nonionic surfactants onto solids via liquid chromatograph mass spectra analysis.

The sorption characteristics of three Triton series surfactants (Triton-100, Triton-305, and Triton-405) from aqueous solution onto four different solids with a wide range of organic matter (OM) content were studied through the liquid chromatograph mass spectrometry (LC-MS) analysis. The examined surfactant concentrations ranged from below to above the critical micelle concentration (CMC) of the selected surfactants. A parameter, Phi, defined as the ratio of the average ethylene oxide (EO) number of surfactant on the adsorbed phase to that in the aqueous solution, was used to distinguish the controlling mechanism (adsorption or partitioning) of surfactants from aqueous solution onto the solids. For solids with very low OM content, adsorption was the primary mechanism and the Phi values were found to be larger than 1.0 and might reduce to 1.0 with the increasing surfactant concentration. On the other hand, the Phi values for solids with very high content of OM were equal to or less than 1.0 and remained constant as the surfactant concentrations varied, in which partitioning was the most likely dominant mechanism. For solids with an intermediate content of OM, adsorption and partitioning mechanisms coexisted and the Phi values could be larger or less than 1.0 and decreased with the increasing surfactant concentration.

Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis.

The adsorption of Remazol black 13 (Reactive) dye onto chitosan in aqueous solutions was investigated. Experiments were carried out as function of contact time, initial dye concentration (100-300mg/L), particle size (0.177, 0.384, 1.651mm), pH (6.7-9.0), and temperature (30-60 degrees C). The equilibrium adsorption data of reactive dye on chitosan were analyzed by Langmuir and Freundlich models. The maximum adsorption capacity (qm) has been found to be 91.47-130.0mg/g. The amino group nature of the chitosan provided reasonable dye removal capability. The kinetics of reactive dye adsorption nicely followed the pseudo-first and second-order rate expression which demonstrates that intraparticle diffusion plays a significant role in the adsorption mechanism. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (0.212kJ/mol) indicated that the adsorption is endothermic process. The results indicate that chitosan is suitable as adsorbent material for adsorption of reactive dye form aqueous solutions.

Statistical optimization of medium components and growth conditions by response surface methodology to enhance phenol degradation by Pseudomonas putida.

In this work, a four-level Box-Behnken factorial design was employed combining with response surface methodology (RSM) to optimize the medium composition for the degradation of phenol by pseudomonas putida (ATCC 31800). A mathematical model was then developed to show the effect of each medium composition and their interactions on the biodegradation of phenol. Response surface method was using four levels like glucose, yeast extract, ammonium sulfate and sodium chloride, which also enabled the identification of significant effects of interactions for the batch studies. The biodegradation of phenol on Pseudomonas putida (ATCC 31800) was determined to be pH-dependent and the maximum degradation capacity of microorganism at 30 degrees C when the phenol concentration was 0.2 g/L and the pH of the solution was 7.0. Second order polynomial regression model was used for analysis of the experiment. Cubic and quadratic terms were incorporated into the regression model through variable selection procedures. The experimental values are in good agreement with predicted values and the correlation coefficient was found to be 0.9980.

Application of artificial neural network model for the development of optimized complex medium for phenol degradation using Pseudomonas pictorum (NICM 2074).

Biodegradation of phenol using Pseudomonas pictorum (NICM 2074) a potential biodegradant of phenol was investigated for its degrading potential under different operating conditions. The neural network input parameter set consisted of the same set of four levels of maltose (0.025, 0.05, 0.075 g/l), phosphate (3, 12.5, 22 g/l), pH (7, 8, 9) and temperature (30 degrees C, 32 degrees C, 34 degrees C) on phenol degradation was investigated and a Artificial Neural Network (ANN) model was developed to predict the extent of degradation. The learning, recall and generalization characteristic of neural networks was studied using phenol degradation system data. The efficiency of the model generated by the ANN, was tested and compared with the results obtained from an established second order polynomial multiple regression analysis (MRA). Further, the two models (ANN and MRA) were used to predict the percentage of degradation of phenol for blind test data. Performance of both the models were validated in the cases of training and test data, ANN was recommended based on the following higher coefficient of determination R (2); lower standard error of residuals and lower mean absolute percentage deviation.

The structural and sorptive characteristics of high-surface-area carbonaceous material (HSACM) in soils.

The structural and sorptive characteristics of the high-surface-area carbonaceous material (HSACM) isolated from soils were investigated. The HSACM contents in soils were first identified by the organic petrology method. A novel isolation method using acid demineralization, base extraction, and ZnBr(2) floatation sequential steps was developed to extract the HSACM from soil. The differences in structural and sorptive characteristics with the HSACM and the intact soil were investigated using nitrogen adsorption isotherms and trichloroethylene (TCE) sorption isotherms at low concentrations (0 to about 2 mg/L) both with and without tetrachloroethylene (PCE) as the cosolute. It was found that HSACM possesses a much higher specific surface area and pore volume as well as a smaller pore size than the original soil. Moreover, the sorption of TCE to HSACM is noticeably more nonlinear and competitive than to the original soil. A small amount of highly adsorptive HSACM is largely responsible for the nonlinear soil sorption of a single solute at very low concentrations.