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Yasuyuki Egashira, Yutaka Genchi, Toshinori Kojima, Yuji Sakai, Kenji ...
2010 Volume 36 Issue 4 Pages
199
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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Mikiya Tanaka, Hirokazu Narita, Yukinori Saiki
Article type: Reviews
2010 Volume 36 Issue 4 Pages
201-206
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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/dm
3 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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Atsushi Iizuka, Akihiro Yamasaki, Yukio Yanagisawa
Article type: Reviews
2010 Volume 36 Issue 4 Pages
207-211
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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 (CaCO
3). By utilizing this reaction, CaCO
3 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 (CO
2). The process is considered to be a promising option for waste concrete recycling.
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Yoichi Kodera, Mushtaq A. Memon
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
212-221
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Yoshiro Maki, Junji Shibata, Norihiro Murayama, Yasuhiro Nishimura, Yu ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
222-228
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Shohei Riya, Sheng Zhou, Yutaka Nakashimada, Akihiko Terada, Masaaki H ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
229-236
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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We evaluated direct and indirect greenhouse gas (methane (CH
4) and nitrous oxide (N
2O)) 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 CH
4-C from the CW were lower than those reported in the literature. Direct fluxes of N
2O-N exhibited positive (14 out of 41 sampling times) and negative (13 out of 41 sampling times) values, resulting in average N
2O-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. N
2O-N concentration in the filtered water ranged from 0.43 to 10.4 μg-N·
l−1 and significantly correlated with NO
3-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 CH
4-C and N
2O-N, respectively. Emission factor (
EF5g) of the indirect N
2O-N emission was 0.00053–0.0086 kg N
2O-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 N
2O-N emission from a vertical flow constructed wetland.
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Toshinori Kojima, Jun Nagamine
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
237-242
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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The artificial weathering of alkaline rocks, which are abundant resources, is thought to be one possible countermeasure for CO
2 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/m
2·h. The dissolution rates of CaSiO
3 and CaCO
3 were found to be highest.
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Kazuya Mayumi, Yasunori Kikuchi, Jun Nakatani, Masahiko Hirao
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
243-254
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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 CO
2 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 CO
2 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 CO
2 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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Yukiko Shimada, Teppei Niide, Fukiko Kubota, Noriho Kamiya, Masahiro G ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
255-258
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Yutaka Morikawa, Masako Ito, Shinitch Umeda
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
259-263
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Yurie Mine, Mayumi Oyabu, Akino Itoh, Akiko Nishida, Kimitoshi Fukunag ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
264-269
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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 m
2/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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Hisashi Inazuka, Takeshi Ogata, Kenji Takeshita
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
270-274
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Yuji Sakai, Tomoyuki Aihara, Takayoshi Yamamoto, Masayoshi Sadakata
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
275-280
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Yuji Sakai, Takayuki Seki, Kiyotaka Sato, Qun Chen, Hidetoshi Nagamoto ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
281-287
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Koshiro Tamaoki, Norizo Saito, Takashi Ogi, Toshiyuki Nomura, Yasuhiro ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
288-292
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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/m
3 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 PdCl
2 solution was 5 mol/m
3. The recovery capacity of
S. algae cells was determined as 1.49 g-Pd/g-dry cells, indicating that the 10 mol/m
3 aqueous PdCl
2 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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Fumihiko Ogata, Hitoshi Yabutani, Hisato Tominaga, Isao Yamaguchi, Nao ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
293-298
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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To investigate the recycling of coffee grounds (CGs), the surfaces of CGs were modified with CaCl
2 solution, and the adsorption mechanism of NO
3−-N and NO
2−-N on these surfaces was evaluated. Maximun adsorption of NO
3−-N and NO
2−-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 NO
3−-N and NO
2−-N adsorbed. The adsorption isotherms of NO
3−-N and NO
2−-N were fitted by the Freundlich and the Langmuir equations. These results indicated that NO
3−-N and NO
2−-N were adsorbed onto CG600 by ion exchange. CGs treated with CaCl
2 solution can be utilized for the removal of NO
3−-N and NO
2−-N from drinking water.
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Tetsuo Oishi, Hirokazu Konishi, Toshiyuki Nohira, Mikiya Tanaka, Tateo ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
299-303
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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, DyCl
3 was added to the anolyte, and the container was alloyed with Dy by potentiostatic electrolysis. Second, NdCl
3 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–DyCl
3–LaCl
3 systems with and without FeCl
2, in order to confirm the selectivity during the alloying step. Regardless of the presence of FeCl
2, DyNi
2 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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Satoshi Nakai, Koujiro Kawakami, Tetsuji Okuda, Wataru Nishijima, Mits ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
304-309
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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 m
3 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 m
l·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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Hidetaka Arai, Atsushi Ogata, Akihiro Yamasaki, Hyun-Ha Kim, Yukio Yan ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
310-316
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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Toluene decomposition was carried out using nonthermal plasma reactors, which were packed with spherical ferroelectric pellets [SrTiO
3 (ε=330) or BaTiO
3 (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 SrTiO
3 and BaTiO
3, 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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Masahiro Wakatsuki, Atsushi Iizuka, Akihiro Yamasaki, Yukio Yanagisawa
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
317-322
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Hiroyuki Harada, Yoshimasa Amano, Masahiko Shiki, Kenji Yoshino, Koich ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
323-327
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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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Hideaki Higashino, Hideko Motojima, Masuo Ozaki
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
328-335
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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 m
3 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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Wenqing Zhang, Masanori Ishihara, Toshinori Kojima
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
336-342
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
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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/m
3 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/m
3 N, being well below the regulation standard value effective since Dec. 2002 of 5 ng-TEQ/m
3 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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Hisayoshi Umeda, Atsushi Sasaki, Kunihiko Takahashi, Yasushi Takasaki, ...
Article type: Research Papers
2010 Volume 36 Issue 4 Pages
343-350
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
JOURNAL
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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 (NH
4+) 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 NaBH
4 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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Hiroyuki Hamano, Nobuhide Takahashi, Koichi Yamada, Toshinori Kojima, ...
Article type: Notes
2010 Volume 36 Issue 4 Pages
351-354
Published: July 20, 2010
Released on J-STAGE: July 21, 2010
JOURNAL
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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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