Development of a dye nanoparticle-loaded test strip for the Zn(II) determination in metal plating wastes.

Zincon/Latex-NR3+ nanocomposite-loaded dye nanoparticle coated test strip (Zincon/Latex-NR3+ DNTS) was fabricated to detect Zn(II) in plating wastewater by a unique color change from red-purple to deep blue and evaluated its detection performance in actual plating samples. The 5 × 5 mm square-cut DNTS attached sticks were immersed into 10 mL aliquots of aqueous solutions containing Zn(II) ion and 0.01 M TAPS buffer at pH 8.4 with stirring at 250 rpm for 60 min. The calibration curve for Zn(II) was prepared based on the integrated area intensity of reflectance by TLC at 620 nm with the 3σ detection limit was 48.61 ppb, and the quantitative range was approximately up to 1000 ppb. Although Cu(II), Mn(II), Ni(II), and Co(II) showed competitive interference due to complex formation with Zincon, a mixture of masking reagent including thiourea, 2-aminoethanthiol, and o-phenanthroline was effective in removing the contamination. To eliminate Cr(III) interference based on the incorporation of Zn(II) into Cr(III) hydrolyzed polymer, adding KBrO3 and H2SO4 under boiling for several minutes was required. With appropriate pretreatment, all results of actual plating water samples by Zincon/LatexNR3+ DNTS were close to those of ICP-OES.

Correlation between the Porosity and Permeability of a Polymer Filter Fabricated via CO2-Assisted Polymer Compression.

A porous filter was fabricated by plasticizing polymer fibers with CO2, followed by pressing and adhering; then, its gas permeability, a basic physical property of filters, was measured using N2. The as-obtained filter was well compressed and expected to approximate a sintered porous material. Therefore, the fabricated filter was analyzed by applying the Darcy law, and the correlation between its gas permeability and porosity was clarified. The gas permeability decreased owing to both pore size and porosity reduction upon increasing the degree of compression, which is a feature of the CO2-assisted polymer compression method. In particular, without any contradiction of pore size data previously reported, the gas permeability was clearly determined by the filter porosity and pore size. This study can serve as a guide for designing filters via CO2-assisted polymer compression.

Analysis of Sustained Release Behavior of Drug-Containing Tablet Prepared by CO2-Assisted Polymer Compression.

A controlled-release system for drug delivery allows the continuous supply of a drug to the target region at a predetermined rate for a specified period of time. Herein, the sustained release behavior of a drug-containing tablet fabricated through CO2-assisted polymer compression (CAPC) was investigated. CAPC involves placing the drug in the center of a nonwoven fabric, sandwiching this fabric between an integer number of nonwoven fabrics, and applying pressure bonding. An elution test, in which the drug-carrying tablet was immersed in water, showed that sustained-release performance can be controlled by the number of nonwoven fabrics covering the top and bottom of the drug-loaded fabric and compression conditions. A model of sustained drug release was formulated to estimate the effective diffusion coefficient in the porous material. Comparative analysis of the bulk diffusion coefficient revealed that the change in diffusion volume due to change in porosity predominates. The tortuosity of the diffusion path was 3⁻4, and tended to remain almost constant or increase only slightly when the compression rate was increased. These findings show that sustained drug release can be controlled by incorporating the drug into a nonwoven fabric and using the same raw material to encapsulate it.

Visual detection of arsenic using hydride generation followed by reaction with silver bis(2-ethylhexyl)dithiocarbamate retained in a support filter.

In this study, a simple and effective method for the detection of trace amounts of arsenic in water samples was developed. Arsenic hydride generated by the reduction of a water sample was passed through a sensing filter retaining silver bis(2-ethylhexyl)dithiocarbamate complex. The original yellow color of the filter immediately turned reddish violet. The difference of color was observed by a reflection spectrophotometer. Sensing filters made of glass fiber gave the highest sensitivity. Addition of low volatile amines effectively stabilized the performance of the sensing filter. Common anions including phosphate ion did not interfere with the arsenic detection. Visual detection of 10 µg dm(-3) was achieved in φ10 mm filter area using 60 cm(3) of sample solution.

Importance of the support material in thin palladium composite membranes for steady hydrogen permeation at elevated temperatures.

Hydrogen permeation performance of palladium membranes supported on porous alpha-alumina and yttria-stabilized zirconia (YSZ) was studied at 300-850 degrees C. The hydrogen permeation flux across the palladium-alpha-alumina membrane decreased markedly during permeation tests conducted at >600 degrees C. The SEM and XPS studies of the post-test membrane revealed the presence of aluminium in the palladium layer. Such migration of aluminium was not observed by heating the palladium-alpha-alumina membrane under an argon atmosphere, indicating that hydrogen is responsible for this phenomenon. Hydrogen-induced strong metal-support interaction might be related to this considerable loss of the hydrogen flux. Reduction of alumina to Al(0) by active hydrogen at the membrane-support interface and subsequent migration of Al(0) into the palladium layer represents the most plausible mechanism for the aluminium diffusion. Actually, Al(0) that migrated into the palladium membrane layer generated less hydrogen-permeable palladium-aluminium alloy or inter-metallic compound phase. In contrast, no such strong interaction was found between the YSZ support and the palladium membrane. This composite membrane exhibited a steady permeation of hydrogen at 650 degrees C for 336 h. Having a remarkably high reduction potential, Y(III) is unlikely to be reduced to Y(0), although Zr(IV) has a comparable reduction potential to that of Al(III). A binary phase diagram shows a liquid alloy phase present for the Pd/Al couple at temperatures greater than 615 degrees C (eutectic point), while an inter-metallic compound or liquid alloy phase in the Pd-Zr binary system is not apparent at temperatures less than 750 degrees C. Consequently, inter-diffusion of zirconium with palladium did not occur during operations at 650 degrees C.

Supercritical water decomposition of polyethylene samples for the determination of their trace cadmium content.

A novel pretreatment method has been developed for determination of toxic metals in plastic materials by their decomposition under supercritical water conditions. Particularly, quantitative analysis of cadmium in polyethylene has been demonstrated using inductively coupled plasma atomic emission spectrometry combined with supercritical water treatment. All the cadmium in a polyethylene sample was obtained as an aqueous solution by the treatment with supercritical water containing 12.4% of hydrogen peroxide at 673 K. Although a complete recovery of the aqueous solution from the reactors has not yet been attained, we verified that the present method was effective and promising for quantitative analysis of trace amounts of hazardous metals in plastic materials.

Separation and enrichment of arsenic(V) with composite resin beads containing magnetite crystals.

The adsorption of arsenic(V) was investigated using macroporous resin beads containing magnetite crystals. Arsenic(V) was favorably adsorbed at pH 2-9, where the distribution coefficients were larger than 10(3). The maximum capacity was 0.050 mmol/g. Metal cations including Ca(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and La(III) did not give serious interference at 10(-4) M level. Diluted arsenic(V) was collected with a packed column, and the retained arsenic(V) was quantitatively eluted out with 1 M NaOH.

Solvent extraction of arsenic(V) with dispersed ultrafine magnetite particles.

The solvent extraction of arsenic(V) was investigated using heptane containing ultrafine magnetite particles and hydrophobic ammonium salt. Arsenic(V) was favorably extracted from aqueous solutions of pH ranging over 2-7, where the distribution ratio (10(3)) was independent of the pH. Although the addition of alkyl ammonium salt improved the phase separation, no notable influence was observed on the extraction of arsenic(V). Oleic acid suppressed the distribution ratio of arsenic(V) when the concentration exceeded 10(-2) M. Sulfate did not interfere with the extraction, while the presence of more than 10(-3) M phosphate decreased the distribution ratio. Metal cations including calcium(II), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and lanthanum(III) did not give any serious interference up to the 10(-4) M level. According to equilibrium and kinetic studies, the extraction of arsenic(V) can be interpreted by the adsorption of H2AsO4- onto the surface of dispersed magnetite particles. The relationship between the amount of arsenic(V) extracted in the organic phase and that remaining in an aqueous phase followed a Langmuir-type equilibrium equation. The maximum uptake capacity was determined to be 4.8 x 10(-4) mol/g-magnetite (36 mg As/g). The arsenic(V) extracted in the organic phase was quantitatively recovered by back-extraction with an alkaline solution.