Endocrine disruptors, such as dioxin and polychlorinated biphenyl (PCB), are affecting the development and reproduction of humans and animals, and are, therefore, of major concern to the environment. In this work, separation from aqueous solutions of several endocrine disruptors such as dibenzo-P-dioxin, diethvlphthalate (DEP) and co-planar PCB (3, 3', 4, 4' -tetrachlorobiphenyl, TCB) has been investigated by pervaporation. The relationship between the separation factor of endocrine disruptors and their physical properties, i.e. saturated vapor pressure (Pvap) and hydrophobicity (log Pow, octanol-water partition coefficient) was discussed. Pervaporation experiments through polydimethylsiloxane (PDMS) membranes were performed using aqueous feed solutions of several endocrine disruptors. The theoretical relationship between α (separation factor) and physical parameters (i.e., Pvap and log Pow) has been developed in this study as follows α∞logPow·pvap(ED) The relationship between the separation factor of endocrine disruptors and log Pow·Pvap (ED) based on the above theoretical equation showed a relative good relationship (r=0.883) as theoretically predicted. We also succeeded to remove endocrine disruptors by pervaporation of sea water at Enoshima island. In summary, hydrophobic endocrine disruptors, such as polychlorinated dioxin and PCBs, can be removed very effectively from an aqueous feed solution and aqueous salt solution using hydrophobic PDMS membranes by pervaporation.
In recent years, numbers and amounts of hazardous chemical substances used for industrial and domestic purposes have rapidly increased. It is said that these substances are finally accumulated in seawater and sediment. However, the distribution and the temporal variation of the hazardous chemical substances in marine environment have not been clarified yet in a global scale due to the limited number of observation data. I believe that more frequent spatial and temporal observations are required in order to understand the marine pollution mechanism.
This study was carried out to improve the analytic accuracy of the low content of hexacyanoferrate (II) contained in table salt. Using a membrane filter, filtration and separation were performed for prussian blue, formed by iron (II) sulfate solution, and the applicability of the methods of measuring Fe intensity by X-ray fluorometry, of dissolving the filter and measuring absorbance was examined. In the presence of NaCl, part of prussian blue dissolved when the filtration filter was washed with water, and the recovery rate fell. However, concentration and separation was performed without forming soluble prussian blue by iron (II) sulfate solution with iron chloride solution (0.005mol/1). Consequently, measurement became possible by employing X-ray fluorometry and absorption spectrochemical analysis. As a result, each calibration curve was observed to be a straight line using the previous two methods, and NaCl had no effect on the measurement. By using this method, measurement of 0.1 mg/kg became possible.
Step motions on NaCl (001) surface were monitored by atomic force microscopic observation following heat treatments of up to 973 K. Thermally activated step motion was first recognized at 723 K. At that temperature, monatomic steps with positive curvature retreated decreasing step lengths, while multi-atomic steps remained intact.Monatomic steps with negative curvature were segmented into non-polar steps, in spite of an increase in the step lengths. The segmented steps became smooth again at 773 K. Atomic motion was restricted on the same terraces up to this temperature. At 873 K, atomic motion from upper to lower terraces was enabled and decomposition of multi atomic steps into monatomic steps was observed, which was interpreted as roughening transition. Mesoscopically, the surface became smoother in 3-dimensions. Although the step energy decreased with an increase in temperature, a preference for electrically neutral steps remained. Complete roughening of the surface due to surface melting was observed after heating to 973 K.
A rapid multielement determination method for trace elements in common salts has been examined by means of ICP-MS (inductively coupled plasma mass spectrometry) and ICP-AES (inductively coupled plasma atomic emission spectrometry) after coprecipitation with magnesium in the salt. The recoveries of trace elements (Al, Mn, Fe, Co, Ni, Cu, Zn, REEs) were in the upper 90%, and major constituents of common salt such as Na, Sr, K, and Ca were significantly reduced in the concentrated solutions. Using magnesium in the salts as a coprecipitant, the blank values of almost all analyte elements were lower than or close to the analytical detection limits. Therefore, it has been found that contamination from copreciptant reagents could be significantly reduced. The present method was applied to the determination of trace elements in commercial table salt. As a result, eight elements could be determined by this method.
Experimental studies on the partitioning of Sr and Mg between gypsum and aqueous solutions indicate that partition coefficients depend on salinity: the partition coefficient for Sr increases with an increase in salinity while that for Mg decreases. In the low salinity region (ca.1-5 times salinity of seawater) the partition coefficient values obtained by this study are in agreement with those of the previous study by Kushnir (1980), but the values for the high salinity region (10-30 times seawater) are different from the previous ones. This difference could be explained in terms of influence of water activity. Using the analytical data on gypsum from low-temperature deposits (evaporite), the partition coefficients for gypsum from low-temperature deposits were calculated. The calculated values for Sr for large crystal gypsum are lower than the experimental values, suggesting that gypsum from low-temperature deposits precipitated more slowly than the experimental gypsum.
Cellulose fibrous sorbent (Chelest Fiber IRY) containing aminopoly carboxylic groups has been used for the preconcentration of indium from aqueous solution in both batch and column experiments. Indium was quantitatively (above 98%) adsorbed on to the Chelest Fiber IRY in the pH range of 2-5.2 (studied pH range 1.2-5.2). The retention of indium on the Chelest Fiber IRY was not affected by the flow rate of sample solution up to 30 mL/min. Based on this result, the solution passed through the column at a flow rate of 20 mL/min. The extracted indium was stripped from the column using 20 mL of 1 mol/L HCl at a flow rate of 4.0 mL/min. The sorption capacity was found to be 0.36±0.01 mmol/g for indium. The adsorbent is chemically stable and adsorption-desorption cycles could be repeated at least 50 times. A high concentration factor of 200 could be achieved. The method could be successfully applied to the separation and determination of indium in solar salt samples.
In recent years, many kinds of salts have come on the market; however, there are few systematic studies about the saltiness of salt. An argument about the taste of salt with or without minerals has been and still is a matter of controversy among consumers. Salt manufacture by ion-exchange membrane process produces more than 99% pure NaCl, while bay salt produced by a salt drying process contains rich minerals (bittern called “nigari” in Japanese) such as CaSO4, MgSO4, MgCl2 and KCl. It is difficult to evaluate how the minerals affect the salt taste quantitatively. In the present study, we examined the saltiness of a mixed solution of sodium chloride, which contains minerals, and salts on the market using a multichannel taste sensor, which comprises different kinds of lipid/polymer membranes as the receptor part of chemical substances. Electric-potential measurement and CPA (Change in membrane Potential due to Adsorption) measurement using the taste sensor enabled us to make a taste map, which is composed of two dimensions. The long-term stability of sensor output for one year was confirmed. Although human sensory evaluations were also made, there was no significant difference among the taste of salts on the market. It means that we can evaluate and control the taste of salts using the taste sensor, because it is possible to detect a slight difference of taste, which is difficult for humans.
Using taste sensor and sensory evaluation, we comprehensively evaluated six types of salts made with different processes through determination of inorganic components and response patterns. Ourresults showed that different contents of inorganic components were detected, engendering different response patterns in a taste sensor and evaluation by sensory tests. It is inferred that the taste sensor response patternis a new and useful tool for evaluating the quality of salt products available on the market.
A simple and fast method for determining chloride ion in sea water was described. The method depends on the color fading reaction of the ternary complex of [Ag (Phen)2] 2BPR through the formation of silver chloride. The ernarycomplex of blue precipitants was neutralized by the addition of gelatin. The measurement time required was 15 min and the color change was blue to red. The proposed method was suitable for comparatively high concentration ofchloride.
We proposed a novel capillary zone electrophoresis (CZE) method with artificial seawater (pH 7.9) as the background electrolyte (BGE) for simultaneous determination of iodide and iodatein seawater. Transient isotachophoresis (ITP) with phosphate as the terminating ion was used as anon-line concentration procedure. The effective mobility of iodide was decreased by the addition of 20 m mol/l cetyltrimethylammonium chloride (CATC) to an artificial seawater BGE so that transient ITP functioned for bothiodide and iodate. Limits of detection (LODs) for iodide and iodate were 4.0 and 5.0 μg/l (as iodine), respectively. The LODs were obtained at a signal-to-noise ratio (S/N) of three. Values of the relative standard deviation (RSD) of migration time, peak area, and peak height for iodide (0.05 mg/1, n=8) were 0.6, 4.2, and 3.6%, respectively. The RSDs of migration time, peak area, and peak height for iodate (0.05 mg/l, n=8) were 0.3, 8.4, and 6.2%, respectively. The proposed method was applied to the simultaneous determination of iodide and iodate in seawater collected around Osaka Bay. A sufficient recovery percentage was obtained for iodide (87-112%) and iodate (93-112%) in the standard additional experiments.
The feasibility of simple determination of trace components (Mg2+, SO42-, k+, Ca2+, Br-) in salt products was studied by wavelength-dispersive X-ray fluorescence spectrometry (XRF/WDX) and an energy-dispersive X-ray fluorescence spectrometry (XRF/EDX) with several preparation methods using model solutions. A filter method, a liquid method, and two types of precipitation methods were adopted for the determination of the components of the salt products. K+, Ca2+ and Br contents were determined using the filter and liquid methods, and Me content was determined with the precipitation method, in which Mg (OH) 2 precipitation was carried out by adding NaOH to the sample solutions. SO42- content was also determined with the precipitation method, in which BaSO4 precipitation was carried out by adding BaCl2 to the sample solutions. The results suggested that the limit for detection in the case of using XRF/WDX was lower than that in the case of using XRF/EDX. The determination accuracy level using the filter method was higher than that using the liquid method. It was suggested that the XRF/WDX using the precipitation and filter methods would be applicable to the determination of the SO42- content of pure salt, the Mg2+, SO42- and Br contents of dried salt, and the contents of all components of common salt.
The conditions for concentrating trace metallic elements in common salt (12 elements: Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V and Zn) using an iminodiacetate-chelating resin disk were examined. These elements were determined by means of inductively coupled plasma atomic emission spectrometry (ICP-AES). Moreover, the amounts of trace metallic elements in common salt were measured under the obtained conditions. As a result, although the 12 elements in water were concentrated simultaneously at pH 4.5, the recovery of some elements (Cd, Mn and Pb) decreased due to the presence of the major components (NaCl, Ca and Mg) of common salt. These elements could be concentrated at pH 8.8. The minimum determination limit of this method was several μg/kg for many elements, when 50 g of sample was processed. The coefficient of variation for repeated measurement of 500 ml of prepared solution added with 2 μg of each element was 5% or less. As a result of measuring trace metallic elements in common salt under the measurement conditions obtained from these above experiments, the determination of the concentrations of many elements was found to be possible. For elements (Cu, Fe, Ni, Ti and Zn) investigated under two pH conditions (pH 4.5 and pH 8.8), the determined values were almost in agreement, and the values for elements of high concentration were in good agreement with the results of direct analysis by ICP-AES.
A numerical analysis is presented in the case where a cold plane water jet is discharged near the free surface of a co-current uniform water flow with linear temperature stratification in a long channel. Reichardt's virtual kinematic viscosity for a turbulent two-dimensional free jet, which has been modified with regard to the size of the discharge port, is used for the governing equation of the present analysis. Also, the virtual Prandtl number is assumed to be 1/2. Examples for the variation of distributions of the stream function and the temperature are described for a 200 m deep the channel, 10 m in width at the discharge port, 1 m/s in the velocity at the discharge port, and 0.05 m/s in the velocity of the main flow. The temperature of the discharged water equals the initial temperature at a depth of 4/5 of the main flow. Initially, the jet flows downwards. However, the distance from the exhaust port to the front of the jet is small. A large eddy that formed behind the jet stream gradually expands, flows downstream of the main flow, and disappears. Finally, a large single circulation flow in the channel is formed. These phenomena are quite different from those hitherto reported about cold water jets discharged into a quiescent water pool with uniform temperature.
A new multiple-effect concentrator of seawater was proposed and the heat and mass transfer in the concentrator was theoretically analyzed. In the concentrator, ten or more thin plates covered with seawater-soaked wicks are arranged vertically with narrow gaps between them, and the heat of vapor condensation on the uncovered surfaces of plates is recovered and used for further evaporation from the wicks on the plates. The heat of hot concentrated seawater and condensate from the concentrator is recovered and used for preheating the seawater fed to the wicks. Along the wicks, the evaporation rate gradually decreases as the salt concentration and the boiling point elevation become higher at distances closer to the concentrate exits. The evaporation is more rapid from the higher temperature wicks which are closer to the first plate heated with supplied vapors since vapor diffusion through gaps is more rapid at higher emperatures. With the greater number of evaporating wicks, the total evaporation rate from all wicks increases to more then 10 times the amount of the supplied vapor for 13 or more wicks, though the production rate of concentrate decreases with the number of wicks because of an increase in the thermal resistance through the plate array. The simple design of the concentrator may greatly reduce the construction cost, and make up for the decrease in production rate.