Affinity of functional groups for membrane surfaces: implications for physically irreversible fouling

Fouling in membranes used for water treatment has been attributed to the presence of natural organic matter (NOM) in water. There have been reports recently on the contribution of hydrophilic fractions of NOM (e.g., carbohydrate-like substances) to fouling, but there is still little information about the physicochemical interactions between membranes and carbohydrate-like substances. In this study, the affinity of carbohydrate-like substances to two different microfiltration (MF) membranes was investigated by using atomic force microscopy (AFM) and functionally modified microspheres. Microspheres were attached to the tip of the cantilever in an AFM apparatus and the adhesion forces working between the microspheres and the membranes were determined. The microspheres used in this study were coated with either hydroxyl groups or carboxyl groups to be used as surrogates of carbohydrate-like substances or humic acid, respectively. Measurements of adhesion force were carried out at pH of 6.8 and the experimental results demonstrated that the adhesion force to membranes was strong in the case of hydroxyl groups but weak in the case of carboxyl groups. The strong adhesion between the hydroxyl group and the membrane surface is explained by the strong hydrogen bond generated. It was also found that the affinity of the hydroxyl group to a polyvinylidenefluoride (PVDF) membrane was much higher than that to a polyethylene (PE) membrane, possibly due to the high electronegative nature of the PVDF polymer. The time course of changes in the affinity of hydroxyl group to a membrane used in a practical condition was investigated by repeatedly carrying out AFM force measurements with PE membrane specimens sampled from a pilot plant operated at an existing water treatment plant. Microspheres exhibited strong affinity to the membrane at the initial stage of operation (within 5 days), but subsequently exponential reduction of the affinity was seen until the end of operation, as a result of fouling development. However, the magnitude of affinity of hydroxyl-modified microspheres was much higher than that of carboxyl-modified microspheres even after the significant reduction of affinity of hydroxyl-modified microspheres to the membranes was seen. The results obtained in this study partially explain why hydrophilic NOM dominated over humic substances in foulants of membranes used for water treatment in recent studies on fouling.     

One-Chip Microcomputer-Based Controller for the McMurray Inverter

Control signals applied to a power converter can be obtained with the aid of microcomputer software. A reliable, low-cost, and small-sized gate circuit can be realized by using microcomputers. The generation of control signals required to control the McMurray inverter are attained by the one-chip microcomputer Intel 8748. The microcomputer generates not only the required firing pulses but monitors the commutating process of the inverter. Once the commutation failure has been detected, the gating sequence is changed to return the system to normal operation, thus realizing the commutation failure-free inverter control.     

Effect of water content of hydrophilic amidoxime polymer on adsorption rate of uranium from seawater

Amidoxime polymers crosslinked with tetraethylene glycol dimethacrylate (40 wt%) and with differing water contents were prepared by poly(acrylonitrile) treatment in various quantities of toluene with hydroxylamine. Adsorption rates of uranium on the amidoxime polymers from seawater were examined in relation to their porosity. The amidoxime polymer prepared from poly(acrylonitrile) in an increasing quantity of toluene exhibits a significantly increasing water content. On the basis of mercury intrusion measurements, the increasing water content was revealed to be predominantly owing to the enhancement of porosity. The adsorption rate of uranium from seawater increased steadily with an increase of porosity, suggesting the dependence of the adsorption rate on a diffusion process of uranium into the pore domain.     

New compound ScTiNbO6 synthesized via phase transformation from anatase to srilankite-like structure

A new srilankite-like compound ScTiNbO₆ was synthesized as a single phase at 900 °C via phase transformation using anatase-type nanoparticles that were directly formed from solution mixture of Sc(NO₃)₃, TiOSO₄, and NbCl₅ under mild and weakly basic hydrothermal condition at 180 °C for 5 h. Anatase-type Sc_0.5Ti₂Nb_0.5O₆ nanoparticles transformed into rutile phase at 1000 °C. The new phase that was appeared via phase transformation was identified as srilankite-like structure with a trace of symptomatic wolframite, α-PbO₂ related structure. The optical band gap of ScTiNbO₆ was 3.58 eV. This titania-base material has potential for application as catalyst and photoluminescence, etc.     

Electrical characteristic of diamond film synthesized by combustion flame

In this study, we attempted to clarify the electrical characteristics of diamond films synthesized by combustion flame and consequently synthesizing a suitable diamond film for use in electronic device applications. When the film contains amorphous carbon, the electrical resistivity (volume resistivity) decreases, i.e., the electrical characteristics of the diamond film worsen. To decrease the content of amorphous carbon in the diamond film, we utilized methods to detect two parameters: optimal equivalent ratio and optimal hydrogen addition rate. These methods can decrease the amount of amorphous carbon effectively, thereby systematically changing the factors influencing the optimal synthesis for improving the film’s electrical characteristics. We have successfully developed a method for producing high-quality diamond films with excellent electrical characteristics and high electrical resistivity (10¹⁰-10¹³ Ω m) at room temperature. This is a paper revealing, explaining and demonstrating the possibility of the controlled electric properties (DC) for diamond films synthesized by combustion flame.     

Influences of monosaccharides and its glycosidic linkage on infrared spectral characteristics of disaccharides in aqueous solutions

The infrared spectral characteristics of ten different types of disaccharides (trehalose, kojibiose, nigerose, maltose, isomaltose, trehalulose, sucrose, turanose, maltulose, and palatinose) and five different types of monosaccharides (glucose, mannose, galactose, talose, and fructose) in aqueous solutions (H2O and D2O) were determined. The infrared spectra were collected using the Fourier transform infrared attenuated total reflectance (FT-IR/ATR) method and comparisons between the degrees of absorption band-shift of the saccharide spectra in the H2O solution with those in the D2O solution with respect to the saccharide concentrations were done. The study revealed that the wavenumber shifts in the bands of mono- and disaccharides in the H2O and D2O solutions could be used as an indicator of the level of interaction between the saccharides and water. The study also focused on the glycosidic linkage position and the constituent monosaccharides and found that they have a significant influence on the infrared spectroscopic characterization of disaccharides in an aqueous solution.     

The dynamics of accessibility and environmental conditions: A characteristic approach to land

We apply the implicit price approach to land to clarify how the various kinds of public expenditure affect land prices. By presupposing that the changing state of typical land characteristics—accessibility and environmental quality—can be expressed in differential equation form, we apply the Maximum Principle to clarify how each of the characteristics of land reacts to public investment in transportation and environmental conservation. We thereby estimate the dynamic behavior of the implicit price of land. The literature suggests that financial resources for further public expenditure (on such aspects as transportation and environmental conservation) should be partly realizable from the increased land price accruing as a result of expenditures in the past.     

Two step explicit finite element method for tsunami wave propagation analysis

Numerical analysis of tsunamis applying the finite element method is presented based on the shallow water wave equation. To discretize time, a two step explicit method is used. The scheme is the extension of the Lax-Wendroff finite difference method. The present finite element method is used for the analysis of the Tokachi-oki Earthquake tsunami problem and compared with the tide gauge records. The conclusion of this paper is that the present method is suitable for the prediction of the tsunami wave propagation problem.     

Preparation and evaluation of Cu2ZnSnS4 thin films by sulfurization of E---B evaporated precursors

By sulfurization of E---B evaporated precursors, CZTS(Cu₂ZnSnS₄) films could be prepared successfully. This semiconductor does not consist of any rare-metal such as In. The X-ray diffraction pattern of CZTS thin films showed that these films had a stannite structure. This study estimated the optical band gap energy as 1.45 eV. The optical absorption coefficient was in the order of 10⁴cm⁻¹. The resistivity was in the the order of 10⁴ Ω cm and the conduction type was p-type. Fabricated solar cells, Al/ZnO/CdS/CZTS/Mo/Soda Lime Glass, showed an open-circuit voltage up to 400 mV.     

Preparation of ion exchange membranes by preirradiation induced grafting of styrene/divinylbenzene into crosslinked PTFE films and successive sulfonation

Ion exchange membranes (IEMs) were prepared by preirradiation induced grafting of styrene with or without divinylbenzene (DVB) into crosslinked polytetrafluoroethylene (RX‐PTFE) films and successively sulfonated by chlorosulfonic acid. The effects of the DVB concentration and solvent on the kinetic of the graft polymerization were studied. The ion exchange capacity (IEC) values of the prepared membranes ranging from 1.5 to 2.8 mequiv/g were obtained. The degree of swelling increased with the increase in the degree of grafting, while higher crosslinking density of both the RX‐PTFE matrices and the grafts suppressed the degree of swelling. The chemical stabilities of the IEMs were tested by recording the weight of the membranes being soaked in hot H₂O₂ solutions. The weight‐time curves of the prepared membranes showed one‐step quick decrease due to the decomposition of the poly(styrene‐sulfonic acid) (PSSA) grafts. Higher crosslinking density in both the RX‐PTFE matrices and the grafts improved the chemical stability of the IEMs. The ionic conductivity of the IEMs increases with the increase in the IEC values. The IEMs with IEC values higher than 2.2 mequiv/g hold the higher ionic conductivity than that of Nafion® 112 membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3587–3599, 2006