Regions with naturally occurring resources containing rare metals are unevenly distributed throughout the world. The Kuroshio, or Black Current, transports various rare metals dissolved in seawater. For example, the amounts of vanadium and molybdenum annually transported by the Kuroshio are 300- and 400-fold, respectively, compaved to the amounts annually consumed in Japan. The reactors of the Fukushima Daiichi Nuclear Power Plant, which were damaged by the Great East Japan Earthquake, caused a meltdown of nuclear fuel and a subsequent hydrogen explosion. By injecting seawater into the reactors for cooling, hundreds of thousands of tons of seawater containing radioactive species was produced. It was stored in the nuclear power plant, but some of it was released to the ocean. Radioisotopes, such as cesium-137, iodine-131, and strontium-90, dissolved in seawater pose a great risk to sea life and thus should be removed and safely confined. We have developed a new preparation technology for fibrous adsorbents capable of selectively collecting ionic species of rare metals in seawater. The fibrous adsorbents containing functional moieties exhibited a high adsorption rate, high adsorption capacity, and are easy use with seawater. Here, the adsorption performance of the novel adsorptive fiber in braid form for the recovery of rare metals and the removal of radioisotopes has been described.
The effect of the amount of proline transporter ProP expression on the mechanism of quick adaptation of Escherichia coli cells under high salinity was analyzed. The ProP gene derived from E. coli expression plasmid was introduced into E. coli cells, and a ProP high expression strain was developed. Under 1.2 M NaCl culture conditions, the growth of normal E. coli cell was inhibited, whereas ProP high expression cells showed remarkable growth. The uptake of proline by E. coli as a compatible solute accorded well with those of cell growth. These data suggested that the amount of proline transporter ProP expression played an important role in quick adaptation of E. coli cells under 1.2 M NaCl culture conditions.
When using a microfiltration/ultrafiltration membrane system for the pretreatment of seawater in a reverse osmosis (SWRO) desalination plant, back washing and air scrubbing are often used to prevent performance deterioration of membrane pretreatment systems.
Although it is common to manage the differential pressure of the membrane unit by monitoring equipment performance, this differential pressure is a whole unit of differential pressure, including the pipes and valves. So the differential pressure of the membrane (trans-membrane pressure, TMP) of itself, which was affected by fouling, is not necessarily measured.
The calculation method for the estimation of TMP and the resistance coefficient using the measured differential pressure of the whole unit and the filtrate flow rate is proposed. Furthermore, the flow rate and TMP at filtration and back washing were examined theoretically for the vertical hollow fiber membrane module, and membrane resistance was calculated.
The effects on the membrane performance recovery of chlorine injection and air scrubbing for back washing in pilot plant operation were examined by analyzing TMP and membrane resistance behavior. With these results, the effectiveness of monitoring membrane resistance was clarified in the operation of a membrane pretreatment system for SWRO plant.