A new practical method for disinfecting drinking water has been developed using anelectrodialysis system with cation-and anion-exchange membranes. The effectiveness of the current densities and flow rates of river water containing bacteria cells passing through a desalting chamber has been studied for practicality. Perfect devitalization of Tamagawa River water is possible using an electrodialysis system with a current density of 0.48 A·dm-2 and a flow rate of 0.6dm3·min-1, and which consumes 7.92 KWH per 1m3, Therefore, the cost of this system is about 160 yen per 1m3 which is slightly more expensive thanthe chlorine disinfection method.
The cation exchange resins were prepared by means of suspension polymerization of styrene (St), methyl methacrylate (MMA), methyl acrylate (MA), and ethyl acrylate (EA) as a monomer, and di-vinyl-benzene (DVB) as a crosslinking agent. The adsorption and desorption characteristics of the resins for calcium and magnesium ions in the artificial seawater and artificial regenerant solution were studied. The polystyrene resin with 4% di-vinyl-benzene crosslinking was sulfonated at 100°C for 10hours, and the sulfonated resins showed the fastest desorption velocity for calcium and magnesium ions. The mechanical strength and amount of swelling decreased with an increase in the degree of crosslinking. The carboxyled ethyl acrylate resin showed greater adsorption capacity for calcium and magnesium ions than the carboxyled methyl acrylate resin.
The ion exchanger for bittern recovery from sea water was studied in terms of adsorption and desorption characteristics for calcium and magnesium ions and compressive strength. The sulfonated styrene-divinyl-benzene (St-DVB), the carboxylated polymethymethacrylate-divinylbenzen (MMA-DVB), the carboxylated polymethylacrylate-divinylbenzen (MA-DVB), and the carboxylated polyethylacrylate-divinylbenzen (EA-DVB) resins were prepared by means of suspension polymerization as an ion exchanger. The ion exchange capacity of the sulfonated polystyrene and the carboxylated polyethylacrylate resins with 8% divinyl-benzene crosslinking were 1.39 and 1.80 [meq/g-wet-Resin], respectively. The characteristics of adsorption and desorption of the St-DVB and the EA-DVB resins remained almost the same as those at the initial stage. The compressive strength of the St-DVB resins with a higher degree of crosslinking decreased along with the adsorption and desorption cycles. But the compressive strength of the EA-DVB resins maintained constant values for 30 cycles.
We developed a new (novel) bundle-shaped fiber adsorbent with amidoxime groups (AO-bundles) that is effective for recovering uranium from seawater. The procedures for preparing AO-bundles are as follows: The bundles of polyacrylonitrile fibers (AN-bundle), that have 30mm in diameter and 60mm in length, were made mechanically with plastic belts (CV-70): AO-bundles were prepared by treating AN-bundles successively with 1M hydroxylamine in methanol and with 1M NaOH solution. AO-bundles treated with 1M hydroxylamine for 8h and with 1M NaOH solution for about 10h showed the maximum adsorption rate and an adsorption ability of 2.0mg/g in 60 days in seawater. Also, the AO-bundle showed high physical stability and its permeability coefficient of seawater in the AO-bundle bed was 3.1×10-5cm2. These results show that AO-bundles are a promising adsorbent for the recovery of uranium in seawater.