Jiunn-Fwu Lee

Adsorption of benzene, toluene, and xylene by two tetramethylammonium-smectites having different charge densities

A high-charge smectite from Arizona [cation-exchange capacity (CEC) = 120 meq/100 g] and a low-charge smectite from Wyoming (CEC = 90 meq/100 g) were used to prepare homoionic tetra-methylammonium (TMA)-clay complexes. The adsorption of benzene, toluene, and o-xylene as vapors by the dry TMA-clays and as solutes from water by the wet TMA-clays was studied. The adsorption of the organic vapors by the dry TMA-smectite samples was strong and apparently consisted of interactions with both the aluminosilicate mineral surfaces and the TMA exchange ions in the interlayers. In the adsorption of organic vapors, the closer packing of TMA ions in the dry high-charge TMA-smectite, compared with the dry low-charge TMA-smectite, resulted in a somewhat higher degree of shape-selective adsorption of benzene, toluene, and xylene. In the presence of water, the adsorption capacities of both samples for the aromatic compounds were significantly reduced, although the uptake of benzene from water by the low-charge TMA-smectite was still substantial. This lower sorption capacity was accompanied by increased shape-selectivity for the aromatic compounds. The reduction in uptake and increased selectivity was much more pronounced for the water-saturated, high-charge TMA-smectite than for the low-charge TMA-smectite. Hydration of the TMA exchange ions and/or the mineral surfaces apparently reduced the accessibility of the aromatic molecules to interlamellar regions. The resulting water-induced sieving effect was greater for the high-charge TMA-smectite due to the higher density of exchanged TMA-ions. The low-charge Wyoming TMA-smectite was a highly effective adsorbent for removing benzene from water and may be useful for purifying benzene-contaminated water.

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.

Behavior of organic polymers in drinking water purification

Synthetic organic polymers used to purify drinking water are severely limited in that their impurities and by-products harm human health. In this study, the undesired effects resulted from chlorination and the enhanced attenuation of toxic organic compounds in drinking water from using synthetic organic polymer coagulants were investigated. In the simulated drinking water purification processes, synthetic organic polymers were used as coagulant aids, reacted with a disinfectant(chlorine) and formed a large number of volatile organic compounds (VOCs). Chloroform and benzene which, are carcinogenic compounds, had the maximum formation potential. Experimental results indicated that the total formation potential of these disinfection by-products significantly increased in the presence of turbidity. On the other hand, adding organic polymers to the coagulation systems resulted in more extensive remove of toxic organic compounds and turbidity. In coagulation and flocculation processes, the formation of clay/polymer complexes can facilitate the removal of toxic organic compounds in contaminated water.

Effective adsorption of heavy metal ions (Cu2+, Pb2+, Zn2+) from aqueous solution by immobilization of adsorbents on Ca-alginate beads

The performance of adsorbent system consisting of orange peel cellulose (OPC), banana peel cellulose (BPC), orange peel cellulose immobilized Ca-alginate beads (OPCCA) and banana peel cellulose immobilized Ca-alginate beads (BPCCA) for the removal of Cu2+, Pb2+, and Zn2+ from an aqueous solution was tested. The widely used Langmuir isotherm model was utilized to describe the adsorption equilibrium process. OPC and BPC were characterized by SEM and Fourier transform infrared spectroscopy (FT–IR) techniques. The concentration of metal ions was varied in order to obtain optimum concentration level. The effect of pH was studied at different pH values. The role of cellulose in the case of OPC and BPC and the role of alginate in OPCCA and BPCCA were well understood leading to two different mechanisms in native and immobilized cellulose. OPC was found to be a better adsorbent among OPC and BPC, and Cu2+ was considered to be adsorbed more effectively than Pb2+ and Zn2+. The extent of enhancement of adsorption capacity in the case of BPC was greater than that of OPC after immobilization. For the same amount of adsorbents used, OPC and OPCCA showed enhanced activity than BPC and BPCCA.

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).

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 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.

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.

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.

Effects of soil properties on surfactant adsorption

Abstract The effects of surface area, soil organic matter (SOM) content, and cation exchange capacity (CEC) of natural soils and clays on the adsorption capacity of cationic, anionic, and nonionic surfactants in water‐solid systems were investigated based on the adsorption isotherm analysis. The sorption capacity for a cationic surfactant was proportional to the CEC of the solids. For both anionic and nonionic surfactants, the sorption capacity was related to the soil mineral fraction. However, other soil properties probably affect the practical sorption. The investigated soil properties were treated case by case.