The ion pair of metal complex with Chrome Azurol S (CAS) and Zephiramine (benzyldimethyltetradecylammonium chloride) was quantitatively collected into the gel of poly (vinyl methyl ether)(PVME). Applying this phenomenon, trace metal ions in aqueous solution could be separated and concentrated into the PVME gel. This gel was separated from the bulk aqueous solution and dissolved into N, N-dimethylformamide (DMF). The metals in the DMF solution were determined by the graphite furnace atomic absorption spectrometry (GFAAS). Using this method, concentration of metals by a factor of100was established, and good separation of trace metal ion from other metal ions was observed. This determination with gel collection was applied to determination of trace metals in sodium chloride and good results were obtained.
Simple, rapid and accurate methods of analysis have been developed based on a new concept of flow injection for determination of minor and trace constituents such as B, SO42-, Ca, Mg, NH4+, Fe, Mn, V, Co, and P in seawater and sea salts which are able to contribute to promote the research works in seawater science and the efficient and advanced uses of seawater resources. Flow injection is effective for solving a variety of problems in conventional chemical methods of analysis. In this paper, basic principle and characteristic advantages of flow injection system are outlined together with showing three typical examples (determination of Ca, Mg, B and SO42- in the salts) among the works developed in the author's laboratory. Through all the developed methods of analysis no complicated manual operation was needed and glass apparatus such as beaker, flask, and pipets usually required for chemical analysis was omitted because most analytical operations were done automatically in a narrow bore PTFE tubing.Those additional advantages over the conventional batch system include low sample and reagent consumption, high sampling frequency, low contamination, easy automation and high sensitivity. Those systems were satisfactorily applied to the analysis of salt and seawater samples.
Trace elements in seawater have attracted a great deal of attention from the viewpoint of bio-resources, local environmental pollution and global material cycles.Many researchers have been trying to develop efficient analytical methods for determination of trace elements in seawater and common salts. Multielement analysis for trace elements has high potential to obtain a large variety of information for an analytical sample.This review introduces recent progresses for multielement determination methods of trace elements in seawater and common salts.
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 of several endocrine disruptors from seawater and aqueous solutions has been investigated by pervaporation method and circulation method using hydrophobic tubes. The relationship between the separation factor of endocrine disruptors and their physical properties, i.e.saturated vapor pressure (Pvap) and hydrophobicity (logPow, octanol-water partition coefficient) in pervaporation was discussed. The theoretical relationship between α (separation factor) and physical parameters (i.e., Pvap, and logPow.) hasbeen developed in this study as follows α∝logPow·Pvap (ED) The relationship between the separation factor of endocrinedisruptors and log Pow·Pvap (ED) based on the above theoretical equation showed a relative good relationship (γ=0.883) as theoretically predicted. We also succeeded to remove endocrine disruptors by pervaporation of seawater and the circulation method using hydrophobic tubes at Enoshima Island. In summary, the concentration of endocrine disruptors in seawater can be analyzed very effectively by the circulation method using hydrophobic PDMS tubes, e.g., the concentration of dibuthylphthalate was around 50 ppb and that of dioctylphthalate was around 7 ppb at Enoshima Island.
Fiber-optic sensors for pCO2 in seawater were developed and their behaviors were studied experimentally and theoretically. The sensor consists of optical fibers, a gaspermeable membrane and a fluorescent indicator solution. The pH change by absorption of CO2 into the indicator solution was monitored by the change in fluorescent intensity. The excitation source was an Ar laser. The excitation light from the laser and the fluorescent light from the reservoir passed through an bundle of optical fibers countercurrently. Two different sensors such as probe-type and flow cell type were developed and compared with each other.The material for gaspermeable membrane was examined for a faster response.The continuous test in the environment to monitorpCO2 was succeeded for a week, but the temperature compensation was required. The further study will be expected for a small-sized sensorwith the different light source and detector.
A multichannel taste sensor comprising different kinds of lipid/polymer membranes as the receptor part of chemical substances can quantify the taste of foodstuffs. In this study, the taste sensor was applied to saltiness of salt. Although many kinds of salts have come on the market, there are few systematic studies about the saltiness. Salt manufacture by an 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 quantitatively how the minerals affect the salt taste. We examined the saltiness of a mixed solution of sodium chloride, which contains minerals, and salts on the market using the taste sensor. As a result, a taste map, which is composed of two dimensions, was obtained. 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.
Adsorption properties of Co and Ni ions were studied with chelating cellulose (Chelest Fiber IRY) containing imminodiacetate fragment as the chelating group. Both Co and Ni ions were quantitatively adsorbed on the adsorbent at above pH 4.5. The sorption capacity was found to be 1.1 mmol/g and 1.4 mmol/g for Co and Ni, respectively. The sample solution containing Co and Ni ions was loaded on a column, packed with 1.0 g of Chelest Fiber IRY at the flow rate of 20 ml/min (SV=6.7min-1). The height of thecolumn section containing 1.0 g of adsorbent is about 20 mm. The retention of these metals on the adsorbent was not influenced by the flow rate of the sample solution up to 27 ml/min. After washing the column with 30 ml distilled water, the adsorbed metal ions were eluted with 20 ml of 1mol/1 HCl at a flow rate of 5.0 ml/min.The method was applied to the determination of Co and Ni in ground water and solar salt samples. The accuracy of the method was demonstrated by recovery on spiked samples
Simulation of an ion-exchange membrane salt manufacturing process for studying the effect of reducing the electric resistance in an ion-exchange membrane on reducing the production cost was performed. The production cost, which is the sum of the energy and equipment costs, was calculated in simulation using an electrodialyzer and a quadruple-effect evaporating composite system. As a result, the energy, the equipment, and the production costs were reduced by 2.5%, 5.6%, and 8.1%, respectively, with 50% reducing of electric resistance of the ion-exchange membrane. The effect of improving of the endurance in the ion-exchange membrane on reducing the production cost was also studied. The production cost was reduced by 8.0% with twice improving of the endurance in the ion-exchange membrane. Therefore it is considered that reducing the production cost by developing the high performance ion-exchange membrane is important.
The simulations of several evaporating salt manufacturing processes (multi-effect process, vapor-compression process and, multi-effect and vapor-compression composite process) that can be realized with present technology were performed.The feasibility of reducing production costs was studied by comparing these processes and an ion-exchange membrane process.As a result, the production costs of the multi-effect process, the vapor-compression process, and the multi-effect and vapor-compression composite process were 1.63, 2.62 and 1.60 times as expensive as the ion-exchange membrane process, respectively. It is confirmed that in order to reduce the production cost using only the evaporating process is difficult.Therefore, reducing the production cost by improving the ion-exchange membrane process is found to be important.
A cool water jet was discharged horizontally into a water channel with thermal stratification, in order to examine the influence of a discharging condition and thermal stratification on the penetration depth of the jet. Major deciding factors in the penetration depth are the discharging temperature and temperature gradient. The influence of the discharging velocity on the penetration depth is minor. The velocity is influential in horizontal distance until the jet begins to sink down. Large eddy simulations (LES) using a non-isotropic Dynamic Smagorinsky model were performed and the numerical results were compared with the experimental results. The numerical results correspond to experimental ones accurately in terms of the penetration depth. It is confirmed that this model is available for simulation of the behavior of a cool jet into thermal stratification. Numerical experiments using this model were performed to examine the relation of each factor in detail. It turned out that both the penetration depth and temperature gradient are correlated with the exponential function. The approximation using this function was suggested to estimate the penetration depth. The approximation was compared with the experimental results. This comparison clarified the application range for practical use of the approximation.