和嶋 隆昌

In recent years, it has been considered to secure water and food using seawater desalination technology, and a new simple desalination material for reducing high concentration sodium chloride in seawater is required. In this study, desalting agents were prepared from natural zeolite with addition of calcined Ca-Fe type layered double hydroxide (LDH) to desalinate seawater for agricultural use. Mordenite type natural zeolite from Fukushima, Japan was used. The salinity and pH of seawater used in this study were 3.61% and 8.0, respectively. When more than 250 g/L of natural zeolite was added, the salinity decreased from about 3.56% to about 2.92% (reduction: about 18.0%) after stirring for 1 h. With higher dosage of calcined Ca-Fe LDH, the reduction time of salinity and the increase of pH became faster, while the reduction rate of salinity was almost same and pH value increased. When the mixture was used at the mixing ratio of natural zeolite and calcined Ca-Fe LDH was 5:4, the salinity decreased to 1.0% (reduction: about 70.0%) after stirring for 1 h, and the pH of the solution increased to 9.0 - 9.7. Radish sprouts could be harvested using seawater treated with a mixture of natural zeolite and calcined Ca-Fe LDH (5: 4), while it was not possible to harvest using seawater and seawater treated with natural zeolite with lower addition of calcined Ca-Fe LDH.

Nitrate contamination of surface waters and groundwater is one of the main problems associated with agricultural activities worldwide, and there is an urgent need to develop effective materials and processes to remove efficiently excess nitrate from aquatic environments. Bittern is a seawater resource that contains large amounts of Mg2+ and Ca2+, and its utilization has received much recent attention. In this study, an Fe-type layered double hydroxide (Fe-LDH) product was prepared from bittern with the addition of an inexpensive agent (FeCl3) for nitrate removal. The greatest nitrate removal was obtained for synthesis conditions of pH 8.5-9.5 at 50 degrees C for 0.5 h. The equilibrium adsorption capacity of the product for nitrate was measured and fitted with the Langmuir and Freundlich isotherm models. The experimental data better fit the Langmuir model than the Freundlich model. The calculated maximum adsorption capacity for nitrate was 0.40 mmol g(-1), which was greater than those of other reported nitrate adsorbents. The product removed nitrate ions from a highly saline solution. The order of interference of anion species for nitrate removal was CO32- > SO42- > Br- > NO2- > Cl- > F-. The pH of the solution and removal of nitrate increased with increasing solution temperature because of ion exchange between the Cl- in Fe-LDH and the NO3- in the solution. Nitrate ions were repeatedly adsorbed and desorbed. The prepared Fe-LDH is expected to be a new inorganic anion exchanger for the removal and recovery of nitrate ions from aquatic environments.

In the crushed stone production process, waste stone-fine slurry is generated as wastewater, and are landfilled as dehydrated cake after some treatments. Recently, it is becoming difficult to secure landfill sites, and effective utilization of by-products, dehydrated cake, is desired. On the other hand, a large amount of coal fly ash was discharged from a coal-fired power plant, due to the operation suspension of nuclear power plants since the Fukushima nuclear accident occurs. In this study, we attempted to prepare geopolymer cement from waste stone-fine slurry with addition of coal fly ask Waste stone-fine slurry used in this study was discharged from one of the quarries in Japan. NaOH solution was added into the slurry, and heated at 60 - 180 degrees C for 0 - 24 h to obtain the high Si solution for preparation of geopolymer cement. After heating, the slurry was cooled to room temperature by quenching with tap water, and various amounts of coal fly ash were added, mixed, and cured at 80 degrees C for 24 k The strength and water purification ability of the product was examined. The solution with high Si content to prepare the geopolymer can be obtained at 120 degrees C for 9 h in 4 - 8 M NaOH solution, and the products obtained from 6 - 8 M NaOH slurry solution with addition of 0.55 - 0.70 weight ratio of coal fly ash have higher strength than other products and Portland cement. The product indicates NH4+ removal ability for wastewater treatment.

Glass fiber reinforced plastics (GFRP) are composite materials with high strength and flame retardancy, and the disposal process is expensive to cause illegal dumping. Therefore, new recycling technology of waste GFRP are desired. In this study, recycling of waste GFRP using pyrolysis with sodium hydroxide (NaOH) under an inert atmosphere was attempted by gasification of resin and conversion of glass fiber into soluble sodium silicate. The pyrolysis behavior of GFRP, the characteristics of the obtained residue, the composition and the yield of generated gas, and the silica extraction into the solution were investigated. As a result, the gasification of the resin and the conversion of the glass fiber into soluble sodium silicate were promoted by pyrolysis with NaOH. It was confirmed that the gas yield, especially flammable gases (H2 and CH4), and the silica extraction increased and the residual ratio decreased as the increase of the heating temperature, NaOH addition and heating time.

Zeolites A and X, well-known as practical materials, were successfully synthesized with high cation exchange capacity (CEC) using two industrial wastes, waste crushed stone powder and aluminum dross, by alkali fusion treatment. Waste stone powder and aluminum dross are industrial wastes, and effective utilization of these wastes has been highly expected. Since the main components of the two wastes are Si, Al and O, those wastes can be used as starting materials for synthesis of zeolites. In this study, these industrial wastes were converted into crystalline zeolite-X and –A using alkali fusion. The stone powder, dross and the mixture of these wastes were transformed into a soluble phase via alkali fusion, and then agitated in distilled water at room temperature to give an intermediate gel-like solid, followed by synthesis at 80 °C to give the final product. The zeolites were successfully synthesized via the alkali fusion process, and selective synthesis of zeolites A and X was achieved by controlling the mixing ratio of aluminium dross to stone powder.