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.

Blast furnace (BF) slag, one of the byproducts of iron- and steel-making plants, was converted to a product, including a hydrogrossular, through the alkali fusion method for HCl gas removal. BF slag was transformed to the alkali-fused slag with reactive phases via alkali fusion, and then, the fused slag was added to distilled water and stirred at room temperature to prepare the precursor for the synthesis of the product including a hydrogrossular by heating. The effects of the mixing ratio of NaOH to slag (NaOH/slag ratio), fusion temperature, ratio of the fused slag mass to distilled water volume (W/V ratio), stirring time, heating time, and heating temperature of the product phase were investigated, and the HCl gas removal ability of the obtained product was determined. The optimal conditions for hydrogrossular synthesis are NaOH/slag ratio of 1.6, fusion temperature of 600 degrees C, W/V ratio of 125 g/L, stirring time of 24 h, heating temperature of 80 degrees C, and heating time of. 3-6 h. The product removed more HCl gas than the BF slag and showed higher Cl fixation than lime. These results suggest that a novel scavenger for HCl gas removal at high temperature can be synthesized from the BF slag through alkali fusion.

A novel carbonaceous immobilizing agent for heavy metal contaminated soil was prepared from bamboo using sulfur immersion and pyrolysis, and the lead immobilization in artificial contaminated soils using sulfur-impregnated carbonaceous material was estimated. The bamboo was powdered, dried, and then immersed in 0.1 - 1 M K2S solution for 0 - 24 h to prepare sulfur-immersed materials. The immersed-materials were heated at 400 degrees C for 1 h in nitrogen gas to produce the sulfur-impregnated carbonaceous material by pyrolysis. The abilities of the product to immobilize lead from aqueous solution were examined to obtain the products with high lead immobilization ability. With increasing K2S concentration, the immobilization ability of the product for lead gradually increases and then above 0.75 M K2S those are almost constant, while 15 min is sufficient for the immersed time to obtain the product with high lead immobilization ability. The product prepared from material immersed in more than 0.75 M K2S solution for more than 15 min has a maximum immobilization ability for lead ion of 2.78 mg/g. The lead immobilization using the sulfur-impregnated product is sustainable due to the formation of leadhillite [Pb4SO4(CO3)(2)(OH)(2)] and shannonite [PbCO3 center dot PbO]. The product can immobilize lead ion in various artificial lead-contaminated soils. By mixing artificial lead-contaminated soil with the sulfur-impregnated product, the eluted solution became neutral, and the eluted concentrations of lead ion dropped below the Japanese elution standard for soil.

A novel carbonaceous adsorbent was prepared from sulfur-impregnated heavy oil ash via pyrolysis using potassium sulfide (K2S) solution, and its ability to remove lead (Pb2+) from aqueous solutions was examined. It was compared with an adsorbent synthesized by conventional pyrolysis using potassium hydroxide (KOH) solution. Specifically, the raw ash was immersed in 1 M K2S solution or 1 M KOH solution for 1 day and subsequently heated at 100-1000 degrees C in a nitrogen (N-2) atmosphere. After heating for 1 h, the solid was naturally cooled in N-2 atmosphere, and subsequently washed and dried to yield the product. Regardless of the pyrolysis temperature, the product generated using K2S (Product-K2S) has a higher sulfur content than that obtained using KOH (Product-KOH). Moreover, Product-K2S has a higher lead removal ability than Product-KOH, whereas the specific surface area of the former is smaller than that of the latter. Product-K2S obtained at 300 degrees C (Product-K2S-300) achieves the highest lead adsorption and a high selective lead removal from a ternary Pb2+-Cu2+-Zn2+ solution. The equilibrium capacity of Product-K2S-300 was found to fit the Langmuir model better than the Freundlich model, and its calculated maximum adsorption capacity is 0.54 mmol/g. From the ternary Pb2+-Cu2+-Zn2+ solution, the order of adsorption by Product-K2S-300 is Pb2+ > Cu2+ > Zn2+, and the removal of Pb2+ and Cu2+ increases as the pH of the solution increases.

The desalination technology of seawater is considered to secure water and food in recent years, and a new simple desalting material to decrease the high concentration of sodium chloride in seawater is desired. In this study, preparation of the desalting agent from two Ca-type clay minerals, natural zeolite and Ca-Fe type layered double hydroxide (LDH), attempted to desalinate seawater for agricultural water[1] [2] [5].Natural zeolites used in this study were mordenite-type zeolite from Fukushima prefecture, Japan and clinoptilolite-type zeolite from Kagoshima prefecture, Japan, and raw and Ca-substituted zeolites were used for seawater desalination[1] [2] [3] [4][5]. Regardless of zeolite type, desalination behaviors of Ca-substituted zeolite were almost same as those of raw zeolite. The salinity and pH of seawater were 3.46% and 8.0, respectively, while clinoptilolite decreased the salinity to 3.20%, mordenite decreased to 2.09%, above 5.0 g/L zeolite addition. As increasing the Calcined Ca-Fe LDH addition to seawater, the salinity decreased to 3.3%, and pH of the solution increased to pH 11.5, and then became almost constant above 2.0 g/L addition of Calcined Ca-Fe LDH. As increasing the mixing ratio of Calcined Ca-Fe LDH to raw mordenite, the salinity decreased to 0.8% (79.2% reduction) while pH of the solution was neutral (about 7.68.0). Radish sprouts could be harvested using the seawater treated with a mixture of raw mordenite-type natural zeolite and Calcined Ca-Fe LDH, although those could not be harvested using seawater, the seawater treated with natural zeolite or Calcined Ca-Fe LDH.

In this study, it was tried to convert simulated lunar rock sand into geopolymer cement by alkali fusion with sodium hydroxide. Space development is currently being conducted in various countries. For construction on the moon, it is difficult to bring all the construction materials from the earth, and development of construction materials made from lunar resources is required. The authors have succeeded in making geopolymer cement from crushed stone dust using alkali fusion. Therefore, there is a possibility that geopolymer cement used for construction material can be made from lunar rock sand, abundantly present on the lunar surface, using the same method. In this experiment, simulated lunar rock sand was fused with NaOH by changing the mixing ratio of the sand and sodium hydroxide, heating temperature, heating time in vacuum or air atmosphere, and the reaction in vacuum and air was compared and examined. As a result, it was found that the elution contents of Si and Al in the fused sand into acid solution increased with increasing the temperature, NaOH addition and heating time of alkali fusion, and the fused reaction in vacuum atmosphere is different from that in air atmosphere.

Incinerated ash with a relatively high Ca content, paper sludge ash, was converted to zeolitic materials with high cation-exchange capacities (CECs) by aging at 80 degrees C in NaOH solution via step-wise acid leaching with HCl to reduce the ash Ca content. The extraction of Ca, Mg, Si, and Al from the ash into the acid solutions during leaching and the products obtained from the leached ash by reaction with an alkali were examined. The contents of Ca and Mg in the ash were more easily extracted from the ash than those of Si and Al in the initial leaching. The leachant pH decreased with increasing numbers of leaching steps, and the amounts of Si, Al, and Ca extracted from the ash increased as a result of the dissolution of gehlenite (Ca2Al2SiO7), one of the main minerals in the ash. Zeolites A and P were synthesized from the leached ashes, and hydroxysodalite was synthesized from the raw ash. With increasing numbers of leaching steps of the ash, the obtained product contained lower released Ca, whereas the product contained higher released Na and has higher CEC, depending on the zeolite phases in the product. The product with the highest CEC was synthesized from third-leached ash, and its CEC was 1.5 mmol/g, which is about four times higher than that of the raw ash (0.4 mmol/g).

Aluminum dross discharged from an aluminum production factory can react with water and emit hazardous gases such as hydrogen and ammonia causing serious environmental pollution. Thus, it becomes necessary to recycle the by-products to avoid such problems. In this study, the feasibility of the alkali fusion process to convert the dross into benign and functional material was investigated. The effects of fusion temperature, dross/NaOH ratio, and the heating time on the amount of gas removed from the dross and the soluble contents of Si and Al in the fused dross were examined. Synthesis of zeolite-A from the fused dross was performed by reacting with sodium silicate. The optimum condition to dissolve the minerals Al and Si and maximize the generation of gases was a fusion temperature of 400 degrees C, the ratio of the raw dross to NaOH of 1.0, and the heating time of 3 h. The fused dross can be converted into zeolite-A product with a high cation exchange capacity (3.22 mmol.g(-1)) by reacting with sodium silicate solution while generating as much gas as that generated in distilled water. These results demonstrate the applicability of the alkali fusion process to recycle the aluminum dross waste generated from an aluminum industry into value-added material, thus contributing to the circular economy while reducing the environmental impact.

In the crushed stone production process, crushed stone fines, such as dust and slurry cake, are generated as by-products, and most of them are landfilled. Recently, it is becoming difficult to secure landfill sites, and effective utilization of by-products is desired. On the other hand, geopolymer cement has attracted attention due to the higher acid resistance than that of ordinary Portland cement. In this study, we attempted to prepare geopolymer cement from crushed stone by-products using alkali fusion. In the experiment, crushed stone dust, discharged from one of the quarries in Japan, the fused dust, which prepared from the dust by heating at 500 degrees f with NaOH addition (weight ratio of addition is 1:1.6) for 0.5 h using rotary kiln, tap water and coal fly ash were used as raw materials. Crushed stone dust, fused dust, and tap water are mixed on various mixed ratio, with or without the addition of coal fly ash, heat at 30 degrees f or 80 C for 24 h, and then stand at room temperature, in the air or distilled water to prepare geopolymer cement. Acid resistances for the obtained product and ordinary Portland cement was also investigated. As a result, 7 g of mixture of crushed stone dust, water and fused dust (mix ratio is 1: 1: 2) with 3 g of coal fly ash, heated at 80 degrees C, and cured in water to obtain the geopolymer cement with hard structure, and the obtained geopolymer cement indicates higher acid resistance than ordinary Portland cement.

The aim of this study is to provide an agricultural cultivation solution from seawater with a simple process using natural zeolite. In the 21st century, the demand for food is increasing due to the global population growth, and securing farmland is one of the most important factors in food production. Approximately 20 % of farmland in the world is salt-damaged soil with unsuitable properties for agriculture by high salinity water, and simple desalination methods of high salinity water to improve salt-damaged soil is desired. Natural zeolite has a cation exchange ability and is available in large quantities at low cost. In this study, desalination of seawater, as high salinity water, using Japanese clinoptilolite zeolites with typical exchangeable cation, Na+, K+, NH4+, Mg2+, and Ca2+, were examined. Ca2+-type zeolite indicates the highest reduction of NaCl from seawater among these ion-exchanged natural zeolites. The column experiment using Ca2+-type natural zeolite shows that pH can be controlled to neutral and salinity can be reduced by the reaction between Ca2+ in zeolite and other ions in seawater. Although Radish sprouts did not grow in seawater, they could be grown in the solution treated with column process of Ca2+-type natural zeolite.

A circulating fluidized bed (CFB) reactor composed of a pyrolyzer and combustor was developed to observe tar emission during pyrolysis of low rank coal. Tar emission in the CFB pyrolyzer was examined under a wide range of operating conditions. Emissions of light tar substances (e.g., benzene, toluene, naphthalene, etc.) could be suppressed at 973 K by enhancement of contact between tar and resultant char in the pyrolyzer (i.e., enhancement of the volatile-char interaction (VCI)). It was also confirmed that about 50% of the heavy tar fraction emissions could be suppressed by the enhancement of VCI at 973 K. These trends were also observed at higher temperature (1173 K). A certain amount of heavy tar was emitted even after enhancement of VCI, so the mechanism of tar elimination was qualitatively determined using Spiral-type TOF-MS. The heavy tar was homogeneously deposited on the char and then was cracked to form lighter fractions by enhanced contact between tar and resultant char during pyrolysis.