Outstanding Paper Award Subcommittee of Kagaku Kogaku Ronbunshu has assessed the 105 papers published in volume 35 into 2009, and the editorial board finally selected the four papers for Kagaku Kogaku Ronbunshu Paper Awards of 2009; those are the papers on “Prevention of Degradation of a Polymer Electrolyte Fuel Cell,” “Release Behavior of Tantalum and Niobium from Refractory Metal Scrap during Chlorination,” “In-situ Measurement of In-plane Temperature Distribution in a Polymer Electrolyte Fuel Cell by Thermography and Clarification of the Factors Causing the In-plane Temperature Distribution,” and “Uniformization of Flow through a Honeycomb Structure by the Lattice Boltzmann Method.”

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Demand is growing for the recovery of nickel from spent electroless nickel plating baths (spent bath). The present authors have been studying the application of solvent extraction to this problem, and their findings are outlined in this review. On the basis of batch extraction experiments, a recycling process was established consisting of two steps: (i) impurity removal, followed by (ii) nickel recovery. In step (i), iron and zinc as impurities in the spent baths are selectively removed using acidic organophosphorous reagent such as PC88A. In step (ii), after increasing the pH to around 6, nickel in the spent baths is extracted using the chelating reagent LIX84I as an extractant aided by a small amount of PC88A as an accelerator. The nickel in the organic phase formed is stripped with 1–2 mol/dm³ of sulfuric acid in order to obtain nickel sulfate solution, which is reused in the plating process. After the nickel extraction step had been validated by the continuous multistage experiment, in which high efficiencies were obtained during the extraction and stripping, this process was introduced in a plating plant and has been stably operated for more than one year. The bath life extension gained by removing impurities or byproducts using solvent extraction was also studied. Zinc in the strike nickel plating bath used for plating on an aluminum surface treated with zincate solution was found to be selectively removed using acidic organophosphorous reagent. This zinc removal process was installed in the plating plant and succeeded in extending the life of the strike bath by 3–5 times.

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Development of a material recycling process for waste concrete is an urgent issue. This paper summarizes the current situation of the issue, and introduces new waste concrete recycling processes via carbonic acid treatment. In the processes, alkaline calcium compounds in the hydrated cement part of waste concrete are extracted and precipitated as calcium carbonate (CaCO₃). By utilizing this reaction, CaCO₃ and clay alternative material can be produced from waste cement particles. Furthermore, combined use of the carbonic acid treatment and conventional mechanical grinding allows fine aggregates to be recycled from waste concrete. The process does not need any additional materials except water and carbon dioxide (CO₂). The process is considered to be a promising option for waste concrete recycling.

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Planning strategies and guidelines for converting waste plastics into fuel were proposed in order to transfer waste-to-energy technologies to developing countries. Unlike integrated solid waste management without resource recovery, commercial fuel production from wastes requires valid coordination among properties of wastes, technologies and product users. Typical points of evaluation were reviewed to select a suitable technology before conducting feasibility studies by a waste management sector and technology provider.

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Experiments to remove heavy metals such as lead, cadmium and copper from artificially contaminated soil were carried out using (S,S)-ethylenediaminedisuccinic acid (EDDS), N,N-dicarboxymethylglutamic acid (GLDA) and citric acid as chelating agents. The chelating agents were tested both separately and in admixture. Elution behavior in a batch operation was investigated by changing the concentration of chelating agents and the treatment time. Since the chelating agents have distinct acid dissociation constants and stability constants in metal ion-complexes, these values provide guidelines for selecting a suitable chelating agent. EDDS has a large stability constant, but dissociation takes place at high pH corresponding to metal hydroxide precipitation, making it difficult to use as a chelating agent for removing heavy metals from the contaminated soil. The mixture of GLDA and citric acid allows lead, cadmium and copper to be eluted at similar velocities and in similar amounts. Based on the batch elution experiments, column continuous tests were carried out to obtain the value of elution velocity. From the elution velocity, calculations and estimates were made as a model for the removal of heavy metals by heap leaching type treatment.

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We evaluated direct and indirect greenhouse gas (methane (CH₄) and nitrous oxide (N₂O)) emissions from a vertical flow constructed wetland (CW) planted with forage rice. The gas fluxes from the CW surface water to the atmosphere (direct emission) and the dissolved gas concentrations in filtered water (indirect emission) from the CW were monitored. Direct and indirect emissions of CH₄-C from the CW were lower than those reported in the literature. Direct fluxes of N₂O-N exhibited positive (14 out of 41 sampling times) and negative (13 out of 41 sampling times) values, resulting in average N₂O-N efflux from and influx to the CW of 17.7±18.8 and −18.9±15.2 μg-N·m⁻²·h⁻¹, respectively. N₂O-N concentration in the filtered water ranged from 0.43 to 10.4 μg-N·l⁻¹ and significantly correlated with NO₃-N concentration in the soil pore water. Given these results, percentages of indirect emission to total (direct+indirect) emission during the experimental period were 2.9 and 86.7% for CH₄-C and N₂O-N, respectively. Emission factor (EF_5g) of the indirect N₂O-N emission was 0.00053–0.0086 kg N₂O-N·(kg-N leaching/runoff)⁻¹, comparable to those of indirect emission sources in the literature. These results indicate the importance of monitoring and controlling indirect N₂O-N emission from a vertical flow constructed wetland.

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The artificial weathering of alkaline rocks, which are abundant resources, is thought to be one possible countermeasure for CO₂ problem by increasing carbon cycle on this planet. From the viewpoint of inorganic chemistry, net fixation of carbon is possible by this measure. However, the rate of fixation may be impracticably slow. In the present paper, the dissolution kinetics of various silicates for industrial applications was investigated.
The dissolution kinetics of mineral ions from silicate rocks suspended in water saturated with carbon dioxide by sufficient flow was measured for 0–600 h at 25°C. The filtered aqueous samples were acidified and then analyzed for the main metal elements.
After an initial rapid increase, the metal ion concentration increased linearly with time and then attained a plateau value. From the linear dissolution stage, the dissolution rate of the mineral was determined. The rate was found to be proportional to the surface area of the sample, irrespective of the ratio of sample amount to water, or its average diameter. It was concluded that the dissolution kinetics was controlled at the mineral surface. The calculated linear rates ranged from 2.1×10⁻⁵ to 7.3×10⁻⁴ mol/m²·h. The dissolution rates of CaSiO₃ and CaCO₃ were found to be highest.

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Plastic recycling system is designed by various stakeholders, such as consumers and recycling manufactures. The effect of plastic recycling depends on conditions on recycle technology, collection, transportation, and the intended products to be substituted by plastic recycling. Therefore, the relationship between the conditions and effects needs to be analyzed in order to design an appropriate recycling system. In this research, we analyzed the relationships between plastic recycling conditions and effects such as the consumption of fossil resources and CO₂ emission toward appropriate Japanese plastic recycling system. An analytic tool utilizing optimization technique was constructed to evaluate and generate plastic recycling scenarios. By this tool, the reduction effect of the consumption of naphtha, fuel oil, coal, and natural gas can be evaluated with the reduction of CO₂ emission through plastic recycling. The system can analyze the optimal distribution scenario of plastic wastes on such reduction effect of fossil resource consumption under specific weighting factors to each resource by linear programming. Based on this analysis, it was demonstrated that 286 sets of weighting factors generated independent 135 candidates. Defining a constraint on the reduction effects of CO₂ emission and naphtha consumption, effective candidates can be selected. If the constraint is that the reduction effects should be higher than 50% of their potentials, 28 scenarios are selected. The constructed system makes it possible to support the design of plastic recycling system from the viewpoints of reducing environmental load including fossil resource consumption.

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Proteins are known to exhibit specific interactions with various metalions. In this study, we investigated two types of protein-rich biomass, chicken feather and hen eggshell membrane, as adsorbents for separation of precious metal ions. Precious metal ions such as Au(III), Pd(II) and Pt(IV) were selectively adsorbed on the biomass in the presence of various transition metal ions. The adsorption capacity of eggshell membrane was higher than that of feather. Adsorption of Au(III) on the eggshell membrane was prominent at a pH range below 5. The adsorption behavior was explained by the complexation of Au(III) ion with proteins in the eggshell membrane and it was affected by Au(III) ion species in the feed aqueous solutions.

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Pre-treatment system of cellulose biomass was investigated for the efficient production of bioethanol by enzymatic hydrolysis. A system of consecutive heating and high-pressure fluid milling was developed in which a part of the upstream piping of the mill was heated, which enables the cellulose biomass to be decomposed in single pass. Two cellulose biomasses, Japanese cedar with lignin and crystalline cellulose (CEOLUS TG (Asahi Chemical Industry Co., Ltd.)) without lignin, were treated by the system. When heated at 453 K (180°C), both samples were decomposed and fibrous particles were observed by SEM microscopy. Using cellulase and hemicellulase, enzymatic hydrolysis of the hydrothermally treated samples was demonstrated. When hydrolysis was performed using CEOLUS treated at various temperatures, high enzymatic degradation ratio was obtained under all heating conditions. Treatment at more than 423 K (150°C) gave a higher degradation ratio. When Japanese cedar samples were treated at 453 K for 110 h, holocellulose degradation ratio was two times higher than that for room temperature treatment, and α-cellulose degradation ratio was approximately three times higher.

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The possibility was examined of using calcium oxide (CaO) as an environmentally friendly catalyst to produce biodiesel fuel (BDF) from oils and fats. The calcium oxide, CaO-E, produced industrially by calcination of limestone in an ambient air, catalyzed the transmethylation of rice oil, but the yield of fatty acid methyl ester (FAME) was only 8.3% in 2 h. However, enhancements of the base amount (>0.77 mmol g⁻¹ of the base strength 7.2≤pK_BH≤15.0), specific surface area (>20 m²/g), and total pore volume of 2–200 nm pore size (>0.19 mL/g) of CaO were achieved by the calcination of calcium hydroxide (Ca(OH)₂) either in vacuo at 425°C for 9 h or 500°C for 1.5 h, or in an atmosphere of nitrogen at normal pressure and 600°C for 4 h correspondingly to the Ca(OH)₂ industrially produced by hydration of the CaO or reagent-grade Ca(OH)₂ (CaO-A, CaO-B, CaO-C, and CaO-D). These calcium oxides exhibited very high catalytic activities in rice oil transmethylation with methanol; the conversion of FAME reached >96% in 2 h.

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The photo-response extraction of precious metal ions was examined, using the azo compound bis(2,2′-dipyridyl-6-yl)diazene (BDPDA), which undergoes reversible trans/cis photoisomerization, adopting the trans configuration under VIS irradiation and being partly photoisomerized to the cis-isomer by UV irradiation. The extraction of platinum ions by BDPDA depended on its configuration, with cis-BDPDA extracting a higher percentage than trans-BDPDA. In the back-extraction, the conversion of BDPDA from cis to trans under VIS irradiation promoted the back-extraction of platinum ions. As a result, platinum ions can be recovered into water without addition of chemicals. These results indicate that the extraction and back-extraction of platinum ions are controllable by controlling the wavelength of irradiation.

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Air pollution, desertification and crop failure are serious problems in China. In order to solve these problems simultaneously, amelioration of desertified soil with gypsum, a by-product of the desulfurization process, has been investigated in northeast China since 1996. With the expansion of the trial area in 1998, an area of no amelioration (ANA) was found where corn could not grow despite 1.0 wt% application of desulfurization gypsum. Additional application of desulfurization gypsum to the ANA in the following year resulted in improvement in germination rate, ratio of growth strain, height of growth strain, thickness of stem, and corn production. Corn production increased with the increase of gypsum application rate and increased year by year, while soil pH and Na concentration decreased. Next, we evaluated the correlations among corn production, gypsum application rate, and ion concentrations in soil solution and found a slightly positive correlation between the increase of corn production and gypsum application. Lastly, the change in water movement in the soil resulting from gypsum application was compared between the area of amelioration (AA) and the ANA. A remarkable amelioration effect of hydraulic conductivity with the increase of gypsum application rate and the decrease of dry density of soil was found in both areas, indicating that the change in water movement in the soil was not the main reason that corn could not grow in the ANA.

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In recent years, the development of new dry desulfurization technology to prevent air pollution has been urgently needed in China. This technology (T-T process) should provide both a high desulfurization rate at lower temperature and useful desulfurization by-products for alkali soil amelioration. In this paper, the combination of zeolite and CaO (Zeolite + CaO) as a new and effective desulfurization sorbent is compared with the conventional sorbent FLASH. The new sorbent gave a desulfurization rate of 72.0% at 473 K, which is lower than the previous temperature. This is thought to be related to increased adsorption of calcium hydroxide resulting from the greater specific surface area of zeolite. In addition, reversing the order of input of calcium oxide and carrier when FLASH and Zeolite + CaO are prepared also increased the desulfurization rate. Both new FLASH and new Zeolite + CaO gave higher desulfurization rates than previous sorbents: 32.4% and 74.9% at 473 K and 623 K, respectively, for FLASH; and 84.1% at 523 K for Zeolite + CaO. This effect is thought to be due to an increase in the specific surface area of sorbent resulting from the input of carrier into a solution in which calcium oxide is dispersed uniformly. Moreover, the value of activation energy indicated that the reaction activity was increased by reversing input order. It was also confirmed that all desulfurization by-products from FLASH, Zeolite + CaO, New FLASH, and New Zeolite + CaO contain gypsum, which is effective for alkali soil amelioration.

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Microbial reduction and recovery of palladium was achieved at 25°C and pH 7 using resting cells of the metal ion-reducing bacterium Shewanella algae when either lactate or formate was provided as an electron donor. The bioreductive recovery of palladium with formate was a fast process: 1–10 mol/m³ aqueous Pd(II) ions were completely reduced to elemental palladium within 60 min. The biogenic precipitates in the S. algae cells were crystalline Pd(0) nanoparticles of less than 10 nm in size. The specific reduction rate of Pd(II) ions reached a maximum of 2.14×10⁻¹⁴ g-Pd/cell/min when the initial concentration of aqueous PdCl₂ solution was 5 mol/m³. The recovery capacity of S. algae cells was determined as 1.49 g-Pd/g-dry cells, indicating that the 10 mol/m³ aqueous PdCl₂ solution was concentrated up to 570-fold by the microbial deposition in the bacterial cells. The biogenic Pd(0) nanoparticles were released from bacterial cells into aqueous solution within 30 min, by ultrasonic treatment of cell suspension with addition of NaOH.

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To investigate the recycling of coffee grounds (CGs), the surfaces of CGs were modified with CaCl₂ solution, and the adsorption mechanism of NO₃⁻-N and NO₂⁻-N on these surfaces was evaluated. Maximun adsorption of NO₃⁻-N and NO₂⁻-N was observed with CGs carbonized at 600°C (CG600), and the amounts adsorbed increased with temperature, at the time of adsorption, reaching equilibrium after 24 h. The amount of chloride ions eluted from CG600 increased with the amount of NO₃⁻-N and NO₂⁻-N adsorbed. The adsorption isotherms of NO₃⁻-N and NO₂⁻-N were fitted by the Freundlich and the Langmuir equations. These results indicated that NO₃⁻-N and NO₂⁻-N were adsorbed onto CG600 by ion exchange. CGs treated with CaCl₂ solution can be utilized for the removal of NO₃⁻-N and NO₂⁻-N from drinking water.

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A new process is proposed for separation and recovery of rare earth metals from wastes. This process utilizes molten salt electrolysis and an alloy diaphragm. The diaphragm functions as a bipolar electrode and enables selective permeation of rare earth ions via the following steps: (a) Rare earth ions are produced by either anodic dissolution of wastes containing rare earth metal or addition of low purity rare earth salts in the anolyte. (b) The rare earth ions are electrochemically reduced at the anolyte side surface of the alloy diaphragm to form rare earth alloy. (c) The rare earth metals in the alloy diffuse to the catholyte side surface of the alloy diaphragm and are dissolved into the catholyte as rare earth ions by anodic oxidation. (d) The rare earth ions in the catholyte are recovered as rare earth metals or alloys on the cathode. Although the diffusion rate of a metal in a solid alloy is generally too low for a separation process, it has been reported that a certain kind of rare earth alloy is formed at an extremely high rate during molten salt electrolysis. Such a phenomenon is applied in the above process. The expected advantages of this process are that rare earth metals will be effectively separated from impurities such as iron-group metals and that the selectivity for each rare earth metal will be controllable by adjusting electrolytic conditions like melt and alloy compositions, potential of the alloy diaphragm, etc. As a preliminary examination, the bottom of a container made of Ni film and containing an eutectic LiCl–KCl melt was immersed in another eutectic LiCl–KCl melt. The inside melt and the outside melt were used as anolyte and catholyte, respectively. First, DyCl₃ was added to the anolyte, and the container was alloyed with Dy by potentiostatic electrolysis. Second, NdCl₃ was added to the anolyte, and a constant current was passed between a carbon anode in the anolyte and an Al plate cathode in the catholyte. The amounts of Dy and Nd in the catholyte were analyzed by ICP-AES. The result indicated that Dy and Nd permeated from the anolyte to the catholyte according to the mechanism mentioned above. Another preliminary examination was performed in LiCl–KCl–DyCl₃–LaCl₃ systems with and without FeCl₂, in order to confirm the selectivity during the alloying step. Regardless of the presence of FeCl₂, DyNi₂ was selectively formed on a Ni plate cathode by potentiostatic electrolysis, which indicates a high possibility of separation of Dy from La and Fe.

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CCA agent consisting of Cu(II), Cr(VI), and As(V) were previously used for preservation of wood products such as ground plates, telegraph poles, and timber. CCA products are not now manufactured in Japan, but about 20,000 m³ of CCA-preserved wood waste is predicted to be produced annually in the coming decades. Under the Construction Materials Recycling Law of 2000, this CCA-preserved wood waste is required to be recycled appropriately. Pulp alternative is one possible destination of recycling that utilizes the properties of wood. For this purpose, CCA removal must be compatible with the conservation of wood components. In this study, an agent for CCA removal was chosen on the basis of CCA distribution in the CCA-preserved wood waste, and then removal of CCA was carried out in conjunction with investigation of the loss of wood components.
Three CCA-preserved wood wastes (samples A, B, and C) were obtained from the CCA-waste storage facility in Chugoku region, Japan. After chipping the wood waste to less than 5 mm, each sample was subjected to an electron probe micro analysis (EPMA) to determine the distribution of CCA. EPMA showed that CCA mainly existed in intra-cellular sections. Since intra-cellular sections contain lignin, which consists of phenolic structures, an oxidizing agent, hydrogen peroxide was chosen for removal of CCA.
For optimized removal using hydrogen peroxide, we investigated effects of 4 operation parameters, including treatment time, temperature, hydrogen peroxide concentration, and solid/liquid ratio (hydrogen peroxide/ CCA-preserved wood waste), on CCA removal and loss of wood components. Finally, removal of CCA was carried out at 90°C for 3 h with 4% hydrogen peroxide in a ratio of 15 ml·g⁻¹. The treatment using hydrogen peroxide attained almost 100% removal efficiencies for Cr and As in samples B & C, whereas the values for sample A were 68% and 66%, respectively. A removal efficiency of more than 95% was observed for Cu in all samples. These results confirmed the feasibility of removing CCA by using hydrogen peroxide, although the removal efficiencies might vary with characteristics of the targeted wood waste. As for wood components, the total weight loss after the treatment was 23%, 22%, and 30% for the samples A, B, and C, respectively, while loss of holocellulose was 23%, 26%, and 30%. Despite these losses, the ratio of holocellulose to total weight in the treated sample was not changed, thereby indicating that the treated wood waste has potential for use as a pulp alternative.

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Toluene decomposition was carried out using nonthermal plasma reactors, which were packed with spherical ferroelectric pellets [SrTiO₃ (ε=330) or BaTiO₃ (ε=15,000)]. The former showed higher efficiencies for toluene decomposition and suppression of NOx formation than the latter. To clarify the difference in effectiveness between SrTiO₃ and BaTiO₃, the waveforms of applied voltage and discharge current were investigated in detail using an oscilloscope. Many discharge current pulses were observed in both reactors when plasma discharge was generated. However, plasma conditions, such as maximum value and numbers of pulsed discharge current peaks in one cycle, differed greatly between the two reactors even at the same input power. The results suggested that plasma conditions could be changed by changing the ferroelectric pellets in the packed-bed plasma reactor. We proposed different models of discharge mode in the two plasma reactors, based on the effect of the ferroelectrics on plasma reaction.

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The effect of a super-absorbent polymer (SAP) on the water-retention characteristics of a model sand layer was studied. A commercially available SAP (Grass Power P-200, supplied by Kurita Kogyo Ltd., Japan) was mixed with a model sand (Toyoura sand) to give an SAP content in the range of 0.05–0.4 wt%. The water-holding capacity of the mixed sand layer was found to increase with increasing SAP content, while the shape of the water characteristic curve was largely unaffected by the SAP content. This result indicates that the water retention capacity of the SAP mixed sand layer is the sum of the water retention capacity of the SAP phase and that of the sand phase. However, the water holding capacity of the SAP phase was reduced by the excess pressure exerted by the weight of the sand layer above the SAP. The effect of the excess pressure on the water-retention capacity was experimentally studied and analyzed, and modeled based on the Flory-Huggins gels model. By considering this excess pressure effect on the water retention capacity of the SAP phase, the water-holding characteristic curve of the SAP mixed sand layer can be well simulated.

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The influence of extracellular polymeric substances originated from benthic algae on particle aggregation and sedimentary stabilization in the Ariake Sea was investigated through laboratory experiment. Extracellar polymeric substances in the lyophilized sediment were isolated as a colloidal carbohydrate fraction. The influence of the polymeric substances on particle aggregation and sedimentary stabilization was experimentally examined through rheological measurement. The rheological properties of polymeric subustances solution and sediment slurry with polymeric subistances in the presence of calcium ions were evaluated using a shear rate changeable rehometer. The aqueous solution of polymeric substances solution behaved as Bingham fluids, and the shear stress increase with elapsed time, probably due to hydration. The sea sediment slurry with polymeric substances behaved as a non-Bingham fluid. The stress–strain hysteresis loop width predicts the interaction of sediment and polymeric substances. Polymeric substances enhance sediment stabilization, and the effect is greatly improve by calcium ions.

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In rural areas of Lombok Island, West Nusa Tenggara Province, Indonesia, cattle raising is an effective measure for improving living standards. However, it carries the risk of water contamination by animal wastes and damages to forests by over-grazing.
With the central and provincial governments pursuing plans to accelerate the development of the area through the promotion of livestock, an increase of animal wastes is expected.
In this study, the effects of a small-scale biogas plant utilizing cattle waste in a cattle-raising farm household are discussed in terms of its impact on the environment.
As a pilot project area, a village in one of the least developed areas in Indonesia was selected.
Firewood is the main household energy source, and collection of firewood causes environmental problems.
Because the biogas plant provided sufficient methane gas for cooking breakfast and lunch for a family of seven members, the reduction of firewood used for cooking was significant, reaching as much as 70% or about 1.9 ton, equivalent to 3.8 m³ of firewood per family per year.
The economic viability of the use of the biogas plant was also studied, and it was found out that the plant is economically feasible under the conditions and circumstances of Lombok Island.

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Incineration of plastic refuse in existing facilities is often said to increase the emissions of harmful gases such as dioxins. In the present study, the change in emissions when plastic refuse mixed with normal burnable refuse was incinerated was investigated using the facilities in Musashino City. In the operation of incinerators, it is necessary firstly to control the generation of dioxins and their precursors in the burning process, and secondly to achieve highly then the highly effective removal in the gas treatment facilities.
The dioxin concentration at the boiler exit or the stack did not show any relationship with plastic content in the mixed refuse for incineration. The dioxin concentrations at the boiler exit ranged 1.2–2.3 ng-TEQ/m³ N, while those at the bagfilter exit were drastically reduced to around 1% of those at the boiler exit. Those at the stack ranged 0.12–0.33 ng-TEQ/m³ N, being well below the regulation standard value effective since Dec. 2002 of 5 ng-TEQ/m³ N for am incinerator with capacity of 2–4 t/h. In conclusion, incineration of burnable refuse mixed with plastic refuse does not result in a drastic increase in dioxin concentration at the stack.
No effects on various other emissions, such as NOx, CO, and HCl, were found, though the treatment cost of HCl may be increased, and the local temperature in the furnace still needs to be measured. Based on these test results, Musashino City decided to collect the plastic as burnable refuse for incineration from October, 2003.

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The strongly acidic wastewaters generated in the process of refining and recycling of precious metals are generally treated by hydrometallurgical routes. For example, wastewaters containing precious metals such as gold, platinum, palladium and silver at concentrations of around 10 mg/L, and other metals such as copper and iron at concentrations ranging from several mg/L to more than 10,000 mg/L, are usually treated by neutralization. However, wastewaters containing a large amount of ammonium ion (NH₄⁺) cannot be treated by general methods of neutralization due to the formation of metal-ammine complexes with increasing pH.
The objective of this work is to recover trace precious metals in strongly acidic wastewater containing a large amount of ammonium ions. When wastewater was neutralized at pH 6, the majority of metals such as copper, lead and iron were precipitated, while precious metals were not precipitated. After neutralization, precious metals remaining in the filtrate were precipitated by NaBH₄ reduction at pH 7.5. In the case of platinum in particular, the reduction was improved by deammoniation with sodium hydroxide. Precious metals were concentrated in copper-metal by combining neutralization, deammoniation, reduction and fusion. Recoveries of gold, silver, and palladium were more than 91%, whereas that of platinum was about 71%.

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Large-scale afforestation of arid land aiming at fixation of atmospheric carbon dioxide requires the effective use of a small amount of rainwater by control of runoff water. Thus it is necessary to estimate the quantity and quality of water available place by place in order to determine a suitable site for afforestation, and then to introduce technologies for improvement of soil structure in order to apply the water to tree growth. However, measured figures are limited, especially for arid land. In the present study, the amount of runoff water was measured to evaluate the water balance at a rainfall event in an area with annual precipitation of around 200 mm. The runoff ratio was determined to be 17.5% for a rare precipitation of 29 mm. The present results will be used to examine validity of our originally developed model.

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Because the flows in agitated vessels are usually three-dimensional, unsteady, and asymmetric, the explicit interpretation of the fluid mixing mechanism as a deterministic process has been difficult even if the flows are laminar. In this study, we have investigated the shape and dynamical behavior of the streakline from the edge of a paddle impeller, and have proposed that the streakline constructs the template for mixing pattern formation. By examining the template, we have explained the mechanism by which the fluid mixing patterns on r–z, θ–z, and θ–r spaces are formed according to deterministic rules. Streaklines lie on a multi-spiral surface that densely covers the whole mixing region, and each forms many lobe structures. Because the streakline lobes invade into other lobes to make a nesting structure, they can densely cover the whole 3-D mixing region and systematically the fine mixing pattern according to the mixing template constituted by the streakline. Moreover, this template is invariant as long as observations are made at the interval of passage of the paddle impeller.

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The motion of a bubble in a flow of shear-thinning fluid under pressure-oscillating field was investigated experimentally. The enhancement of rising velocity of air bubble in shear-thinning fluid was presented by Iwata et al. by applying pressure-oscillation to a quartz cell. The key point is the superposition of a strain field on fluid surrounding the bubble, which results in decreasing shear viscosity. This technique was applied to an in-line process. Pressure-oscillation was achieved by throttled valves upstream and downstream of the branch flow and applying vibration through a diaphragm at the bottom of the test section. Bubbles were introduced by electrolysis from coupled electrodes placed in the flow field. With the help of strobe scope lighting, we successfully monitored the path of the moving bubbles clearly with a high resolution video camera. It was shown that the present method successfully enhanced the bubble rising velocity under a pressure-oscillating field. Additionally, introducing a bubble as a trap inside the flow channel changed the path of a bubble to be removed, and finally enhanced the defoaming performance.

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A spout-fluid bed with a draft tube is one modification of a conventional spouted bed. Here, a 100 mm diameter semi-cylindrical spout-fluid bed with a 14 mm diameter draft tube was used to investigate the effects of flow rates of spouting gas from the central nozzle and auxiliary gas from the conical base distributor and the length of the entrainment zone on the behavior of gas and solid particles in the bed. CO₂ traces were employed to examine gas bypassing characteristics.
Flow patterns of solids can be classified into five flow regimes according to the spouting gas flow rate and the auxiliary gas flow rate. Although the minimum spouting gas velocity decreases with increasing auxiliary gas flow rate, the minimum total gas flow rate for operating a stable spouting mode increases. Gas flow rate through the annulus and solids circulation rate are enhanced when the auxiliary gas flow rate increases or the entrainment zone is extended. Moreover, it was recognized that the gas bypassing flow rate remarkably affects the solids circulation rate.

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A wet porous slab was divided into a dried zone and a wet zone during dielectric drying, and an “accurate method” was proposed to predict thermal power generated in each zone for both microwave drying and highfrequency drying. Furthermore, a “uniform material (UM) approximate method” and a “uniform electric field intensity (UEI) approximate method” were proposed through simplifications of the accurate method. The two approximate methods were compared with the accurate method through calculation examples.
As a result, in a low range of moisture content, the thermal power generated in each zone can be predicted by the UEI approximate method, and the sum of the powers can be predicted by both approximate methods. On the other hand, in the high range of moisture content, the sum of the powers can be predicted only by the UM approximate method, while the thermal power generated in each zone and the sum of the powers cannot be predicted by the UEI approximate method.

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In order to produce sulfites from SO₂ contained in flue gases, an SO₂ absorption experiment was conducted using a gas mixture with oxygen that emulates industrial flue gases. Concentrations of sulfite and sulfate produced by SO₂ absorption were measured, and their production ratios were assessed at a temperature of 303 K. The major product was sulfate when SO₂ was absorbed at a pH of 6.5 or below 4. When the pH of the liquid absorbent was around 4, the major product was sulfite. The production ratio of sulfite can thus be controlled using the pH of the liquid absorbent.

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Steam reforming using solid carbon dioxide absorbent is a high-efficiency production method of hydrogen, which has attracted attention as a source of clean energy.
In our previous study, the use of solid carbon dioxide absorbent supported on electrically heated alumite was proposed. By electrifying the support, the preset temperature can be reached quickly, and the switch between absorption and emission modes can be made easily.
In this study, Li₄SiO₄ was used as CO₂ absorbent, and its support method and CO₂ absorption reaction kinetics were researched. In addition, the feasibility of using the box-type reactor previously proposed was examined.
As a result, a CO₂ absorption plate with an absorption capacity of 30 g/m² was obtained. In absorption reaction dominant region, the activation energy and frequency factor were 1.97×10² kJ/mol, 8.01×10⁹ sec⁻¹ respectively, calculated from the results of kinetic analysis. Using reaction rate equation, the required CO₂ absorption plate surface area was calculated to be about twenty times larger than the reforming catalyst area.
The results suggest that reforming catalyst and CO₂ absorption plate can be introduced into the same reactor by designing the form of the absorption plate.

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This paper presentsanovel method of linear model predictivecontrol (MPC) based on ARXmodels in incremental form. Unmeasured disturbances are popular in industrial control systems and must be treated appropriately. Manystudies have been performed on nonlinear MPC and estimation of unmeasured disturbances. The proposed method provides a robust control algorithm for unmeasured disturbances in a linear MPC framework without using estimation of unmeasured disturbances. The feature of the MPC is an algorithm that can use the AR term of ARX models for unmeasured disturbance as a tuning parameter. The application and performance of the control method are illustrated by simulation of several examples.

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Resin colorant, which is a resin compounding product, is evaluated by whether customers can use it as raw material. Therefore, the resin colorant manufacturer provides a sample for the customer to perform a quality evaluation. This quality evaluation depends on the characteristics and the conditions of manufacture of the resin which the customer uses. Because this information is not disclosed to the colorant manufacturer, who sees only the evaluation results, the manufacturer has to design a recipe for resin colorant (blending ratio of raw materials) in a very uncertain situation. In this situation, the design work depends on the intuition and experience of skilled technical staff.
In this study, we analyzed customers' evaluation results of past experimental recipes and built a model to predict the incidence of defective samples from the mixing ratio, using impact analysis based on independent component analysis. We also developed a design method by which to improve recipe formulation ingredients efficiently in order to reduce the incidence of defective samples at the design stage. In addition, we verified the usefulness of this recipe design method using information on resin colorant recipes produced by Tokyo Ink Corporation. The method was found to agree with the knowledge of skilled personnel and thus to have the potential to contribute significantly to the efficiency of recipe design work.

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A key issue for realizing the thermochemical IS process for hydrogen production is the selection of materials for working with high-temperature acidic solutions of sulfuric acid and hydriodic acid. Glass lining material is a promising candidate, which is composed of steel having good strength and glass having good corrosion resistance. Since the applicability of glass lining material depends strongly on the service condition, corrosion tests using glass used in glass lining material and heat cycle tests using glass lining piping were carried out to examine the possibility of using the glass lining material with high-temperature acidic solutions of sulfuric acid. It was confirmed that the glass lining materials exhibited sufficient corrosion resistance and heat resistance in high-temperature sulfuric acid of the IS process.

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This study was carried out into unexpected nitrogen removal in a fixed bed partial nitrification process, which is an essential pretreatment process for anaerobic ammonium oxidation (anammox). Two statistical methods, multiple regression analysis and the response surface method by spline (RSM-method), were applied to identify the main operational factors for this efficient one-step nitrogen removal using the anammox process. The RSM-method shows the requirements for higher removal rate using explanatory variables with high contribution values. It was found that nitrogen removal rates were obtained under high aeration rates and high flux of influent. It will be possible to attain a high volumetric removal rate of 1.5–2.9 kg-NH₄–N/(m³·d) in this reactor. New anammox bacteria (Asahi-BRW) were detected in this swim-bed reactor, with few detected in the sludge from this reactor. Ammonium oxidizing bacteria, including many types of Nitrosomonas europaea, were detected in free sludge from this reactor.

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