Editor-in-Chief:
Hiroyuki Honda (Nagoya University)

Associate Editors-in-Chiefs:
Manabu Shimada (Hiroshima University)
Takao Tsukada (Tohoku University)

Editors:
Ryuichi Egashira (Tokyo Institute of Technology)
Jun Fukai (Kyushu University)
Choji Fukuhara (Shizuoka University)
Takayuki Hirai (Osaka University)
Masahiko Hirao (The University of Tokyo)
Jun-ichi Horiuchi (Kitami Institute of Technology)
Eiji Iritani (Nagoya University)
Yoshinori Itaya (Gifu University)
Hideo Kameyama (Tokyo University of Agriculture and Technology)
Masahiro Kino-oka (Osaka University)
Toshinori Kojima (Seikei University)
In-Beum Lee (Pohang University of Science and Technology (POSTEC))
Shin Mukai (Hokkaido University)
Akinori Muto (Osaka Prefecture University)
Nobuyoshi Nakagawa (Gunma University)
Hiroyasu Ogino (Osaka Prefecture University)
Naoto Ohmura (Kobe University)
Mitsuhiro Ohta (Muroran Institute of Technology)
Hiroshi Ooshima (Osaka City University)
Yuji Sakai (Kogakuin University)
Noriaki Sano (Kyoto University)
Masahiro Shishido (Yamagata University)
Richard Lee Smith, Jr. (Tohoku University)
Hiroshi Suzuki (Kobe University)
Shigeki Takishima (Hiroshima University)
Yoshifumi Tsuge (Kyushu University)
Tomoya Tsuji (Nihon University)
Da-Ming Wang (National Taiwan University)
Yoshiyuki Yamashita (Tokyo University of Agriculture and Technology)
Miki Yoshimune (National Institute of Advanced Industrial Science and Technology (AIST))

Editorial office:
The Society of Chemical Engineers, Japan
Kyoritsu Building, 4-6-19, Kohinata, Bunkyo-ku
Tokyo 112-0006, Japan
journal@scej.org

AIMS AND SCOPE:

Journal of Chemical Engineering of Japan, an official publication of the Society of Chemical Engineers, Japan, is dedicated to providing timely original research results in the broad field of chemical engineering ranging from fundamental principles to practical applications. Subject areas of this journal are listed below. Research works presented in the journal are considered to have significant and lasting value in chemical engineering.

Physical Properties and Physical Chemistry
Transport Phenomena and Fluid Engineering
Particle Engineering
Separation Engineering
Thermal Engineering
Chemical Reaction Engineering
Process Systems Engineering and Safety
Biochemical Food and Medical Engineering
Micro and Nano Systems
Materials Engineering and Interfacial Phenomena
Energy
Environment
Engineering Education

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It is a great pleasure to publish here a special issue of the Journal of Chemical Engineering of Japan titled, “Sustainable Chemical Engineering.” This special issue has been planned by the voluntary members of the Division of Environment, Society of Chemical Engineers, Japan (SCEJ), and edited by the members as guest editors of the issue. The main purpose of publishing this special issue is to provide opportunities of publishing research and technical topics related to environmental chemical engineering for a wide range of authors and readers interested in this field. This issue includes 21 high-quality articles: 1 review paper and 20 research papers, selected out of 31 submissions through a strict reviewing process by distinguished reviewers. The issue finally covers a wide range of environmental topics from micro-scale to global environment. We believe this special issue is beneficial all the readers of the journal, and stimulate the research activities of the environmental chemical engineering in the future.

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In the present review article, we summarize recent advances in extraction and separation of rare-earth metals using ionic liquids. Rare-earth metals have unique electronic and magnetic properties. In Japan, increasing amounts of rare-earth metals are being used every year in industries employing cutting-edge technology. Therefore, maintaining a stable supply of rare-earth metals is important. In recent times, extensive research has been carried out on the use of ionic liquids for the extraction of rare-earth metals; this is because the extraction ability and/or selectivity for rare-earth metals have been found to increase when using hydrophobic ionic liquids, which have potential applications in liquid–liquid extraction processes. In the octyl(phenyl)-N,N-diisobutyl carbamoylmethyl phosphine oxide (CMPO) extraction system using ionic liquids, the extraction ability was more than 10³ times better than that when using n-dodecane; however, stripping of the extracted metal ions was difficult in the former case. In initial research on the extraction processes based on ionic liquids, industrial extractant PC-88A was employed as well as CMPO, but issues resulting from the low solubility of these extractants and their metal complexes remain to be addressed. To overcome this problem, a new extractant, N,N-dioctyldiglycol amic acid (DODGAA), which is highly soluble in the ionic liquids, has been synthesized. DODGAA shows better performance for the separation of rare-earth metals in ionic liquids than in n-dodecane. Furthermore, a liquid membrane system based on ionic liquids has been developed for the separation and recovery of rare-earth metals. The use of a liquid membrane system may help in reducing the amount of ionic liquids required for metal recovery.

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N,N-Di(2-ethylhexyl)aminomethylquinoline (DEQ) has been newly synthesized to develop selective extractants for precious metals. DEQ is designed so as to exhibit high selectivity for precious metals through the electrostatic force and coordination ability of the tertiary amine and quinoline moieties, respectively. DEQ in toluene exhibits a high selectivity for gold(III), palladium(II) and platinum(IV) over base metals such as copper(II), nickel(II) and cobalt(II) from hydrochloric acid. This is attributed to the strong basicity of the tertiary amine and high coordination ability of quinoline for precious metals. Palladium(II) and platinum(IV) extraction is significantly dependent on the concentration of hydrochloric acid, while gold(III) is quantitatively extracted over the whole concentration region of hydrochloric acid examined. We have quantitatively discussed the extraction equilibria of palladium(II) and platinum(IV) with DEQ in toluene from hydrochloric acid. It is observed that palladium(II) was extracted by the anion exchange mechanism, while platinum(IV) was extracted through the anion exchange and solvation mechanisms. Palladium(II) was extracted as a 1 : 1 complex formed by ion pair formation and coordination bonding, and its extraction equilibrium constant was determined as 1.28 × 10⁷ [-]. Platinum(IV) was extracted as a 1 : 1 complex and a 1 : 2 complex at low and high concentrations of hydrochloric acid, respectively. These extraction equilibrium constants were determined as 4.15 × 10² [mol dm⁻³] and 3.46 × 10⁴ [-], respectively.

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As an alternative using cyanide chemicals for gold extraction, the application of a cyanogenic bacterium viz. Chromobacterium violaceum (C. violaceum) in YP medium has been investigated. The catalytic roles of metal ions such as Na⁺, Mg²⁺, Fe²⁺, and Pb²⁺, as well as the effect of Na₂HPO₄ nutrient addition on the cyanide generation efficiency of the bacterium in this medium have been elucidated. While MgSO₄ and FeSO₄ added to the medium were equally effective for cyanide generation, improved efficiency was obtained in the presence of Na₂HPO₄ and Pb(NO₃)₂. In order to examine the effectiveness of C. violaceum cultured in YP medium for the generation of cyanide ions, the dissolution of gold and copper from waste mobile phone printed circuit boards (PCBs), a good source of gold and copper in alkaline conditions, was tested at 30°C, for various pH values and metal ion contents. Gold leaching was found to be 11% in 8 d at pH 11.0 in presence of 4.0 × 10⁻³ mol/L MgSO₄, whereas; copper recovery was high (11.4%) at pH 10.0. Addition of 1.0 × 10⁻² mol/L Na₂HPO₄ and 3.0 × 10⁻⁶ mol/L Pb(NO₃)₂ to the YP medium increased copper leaching to 30.3% and 38.1%, respectively, at pH 10.0 in 8 d. However, this effect was not observed for gold leaching.

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Experiments have been performed to elute and remove contaminants from artificially contaminated soil using chelating agents such as citric acid, which exists in nature, and N,N-dicarboxymethyl glutamic acid (GLDA), which is biodegradable. The soil was artificially contaminated with heavy metals such as lead, copper, and cadmium. The most effective conditions for batch elution operation using citric acid alone were determined to be 0.1 mol/dm³, pH 3–4, and 30 min shaking time. Since the elution of Pb tended to be slower than that of the other heavy metals, it was determined that this process could be accelerated by adding GLDA to the citric acid. This mixed chelating agent was then used in the column continuous test, which was carried out in order to obtain the elution speed and flow amount required to satisfy the environmental quality standard values regarding contaminated soil. Based on the elution speed obtained from the column operation, guidelines for designing a heap leaching type treatment of contaminated soil are proposed. Treatment of waste solution was investigated using sulfide and hydroxide precipitation methods to remove heavy metal ions. Metal sulfide precipitation method is superior for the removal of metal ions in the presence of citric acid and there seems to be a possibility to reuse chelating agents after removal of metal ions.

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This study investigates the feasibility of zirconium loaded onto orange waste, a cheap and available agricultural waste material, utilization for phosphorus recovery from secondary effluent of piggery wastewater. Phosphorus removal using zirconium-loaded saponified orange juice residue (Zr-SOJR) gel increased with increasing solid/liquid ratio. Phosphate adsorption was found to be very efficient at pH of 2–6. The secondary effluent was treated in a column packed with Zr-SOJR gel, which attained a dynamic adsorption capacity of 1.06 mol-P/kg. The phosphorus adsorbed on the column was successfully eluted as pre-concentrated phosphorus with a small amount of 0.2 M NaOH. Throughout the elution process, zirconium was not leaked from the adsorption gel. The solution obtained after elution had high concentrations of potassium and phosphorus, which was precipitated as potassium–magnesium–phosphate with the addition of magnesium.

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Three varieties of forage rice (Oryza sativa L. cv. Hamasari, Kusahonami, and Leafstar) were transplanted in plots established in a paddy field. Each of these varieties of rice was then subjected either to basal treatment alone (control plots), or to basal treatment plus subsequent treatment with liquid cattle waste (treatment plots). The nitrogen transformations differed significantly between the control plots and the treatment plots. The nitrogen uptake of the plants in the treatment plots was significantly higher than that in the control plants, even though no significant increase was observed in biomass production. A mass-transfer model calculation revealed that ammonia volatilization also increased following slurry application because of the high ammonium concentration and pH of the flood water. However, the total percentages of nitrogen loss through nitrous oxide, ammonia emission, and leaching loss in the treatment plots were only approximately 7–8%, which was significantly lower than the portion assimilated by the rice plant. Moreover, denitrification was considered to be a major pathway for nitrogen removal in the treatment plots; this probably accounted for most of the “Unknown” portion in the nitrogen balance.

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The effect of H₂ addition on the selective catalytic reduction of NO_x with propene (C₃H₆-SCR of NO_x) has been investigated using a metal-monolithic anodic alumina-supported Ag catalyst. The low temperature de-NO_x activity of the Ag/Al₂O₃ catalyst is markedly enhanced by the addition of a small amount of H₂, which is associated with the improved propene activation at low temperatures. The addition of H₂ greatly promotes the nitrate decomposition at low temperatures, which is believed to alleviate nitrate poisoning and initiate the SCR reaction at low temperatures, because of the formation of free silver sites. Furthermore, it is suggested that a small amount of H₂ addition will further reduce the freed Ag⁺ species into Ag_n^δ+ and eventually lead to the improved de-NO_x activity, because Ag_n^δ+ is more active in propene activation than Ag⁺ at low temperatures. However, excess H₂ and high Ag loading mainly promoted the nonselective combustion of propene with oxygen, rather than the selective oxidation of propene with NO_x.

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In this study, a series of catalysts supported on charcoal (C) from thinned wood were synthesized to investigate their activity for catalytic oxidation of volatile organic compounds. To improve the catalyst thermal stability, the charcoal-supported catalyst was thermal-treated at 1000°C in He gas. Charcoal-supported Co, Ni and Fe catalysts (Co/C, Ni/C, Fe/C) were applied to the oxidation of toluene(C₇H₈), and Co/C was the most active among the tested catalysts. Adding Co to the charcoal shifted the thermal stability of charcoal to a higher temperature because some of the carbon was graphitized. Co/C was also applied to oxidation of ethyl acetate (C₄H₈O₂), and showed similar activity for this reaction to Pt/γ-Al₂O₃. No deactivation of the Co/C catalyst was observed during a 40 h durability test.

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With the aim of alleviating the problems of air pollution, soil desertification, and food shortages in China, we have studied the impact of reclamation of alkali soil using the by-products of flue gas desulfurization (FGD). We have developed an evaluation model for assessing the complete economic and environmental impact of the introduction of environmental improvement technologies. The model consists of an economic model based on an input–output table for China and a soil reclamation model. In the context of the introduction of FGD equipment, we are able to calculate the associated changes in economic variables such as real GDP, average wage, labor supply, domestic electricity price, real investment other than for desulfurization equipment, investment in construction, SO₂ emissions in provinces and cities, area of reclaimed alkali soil, and corn and rice production. We simulated the introduction of the wet limestone–gypsum process and/or the integrated desulfurization and water-film dust collection process. The results confirm a reduction in SO₂ emissions and increases in GDP, domestic electricity price, and agricultural production following soil reclamation via the application of desulfurization by-products. In summary, our results confirm the effectiveness of these desulfurization technologies in terms of improving the economy and environment in China.

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This study examines the desulfurization performances of a sorbent derived from waste concrete through thermal gravimetric analysis in the temperature range from 303 to 1173 K. The sorbent is fine particles having a mean diameter distribution of 10–200 μm generated as a byproduct in a recycling process of aggregates from waste concrete. The sorbent is mainly composed of hydrated cement component, i.e. calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)₂). The sorbent showed SO₂ removal activity over the temperature range studied. The desulfurization rate was lower under a lower temperature range up to 773 K, where the desulfurization rate gradually decreased with increasing temperature. The desulfurization activity at the lower temperatures can be attributed to the direct reaction of SO₂ with C-S-H and Ca(OH)₂. For the higher temperature range, the desulfurization rate was much higher, being almost half that for pure calcium carbonate, a conventional sorbent for dry desulfurization.

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Soil salinization has progressed rapidly in northeastern and western China. In addition, air pollution is one of the most serious environmental problems. To alleviate the problems of soil salinization, food shortages, and air pollution, we have studied the amelioration of salt-affected soil using the by-products of flue gas desulfurization (FGD). Moreover, the recycling of waste gypsum produced at both new construction sites and demolition work sites has become a serious challenge in Japan. FGD gypsum in China and gypsum separated from waste gypsum board (WGB) in Japan were added to salt-affected soil as soil amendments. The effects of lignite and peat, which contains humic substances, were also investigated. With treatment, the soil's chemical parameters were restored, and agricultural production increased in all fields. Therefore, we have confirmed the effectiveness of amelioration of salt-affected soil by both FGD and WGB gypsum. Moreover, the use of lignite and peat with gypsum accelerated the effect of soil amelioration. This result suggests that the application rates of both types of gypsum could be reduced. Thus, we can propose a new salt-affected soil reclamation method using WGB, lignite, and peat in China.

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The effect of FeO on volatilization of PbO from CaO–SiO₂–Al₂O₃–FeO molten slag was studied in a lab-scale electric furnace in N₂ atmosphere at a temperature of 1773 K. The employed slag samples consisted of reagent-grade of CaO, SiO₂, Al₂O₃ and FeO mixed at various weight ratios, whose content was adjusted to 2 × 10³ mg-PbO/kg-slag. From the experimental results, it was found that the apparent rate of volatilization of PbO determined by time change of PbO content in the molten slag, increased with an increase in slag basicity which was defined by the weight ratio of CaO to SiO₂, but decreased when CaO was replaced by FeO. The apparent rate of volatilization of PbO, however, was not significantly influenced by slag viscosity, so far as the weight ratio of FeO to CaO in molten slag was controlled at a value of FeO/CaO higher than 0.38. By a comparison of interaction energies between Pb²⁺ and Ca²⁺, Si⁴⁺ and Fe²⁺ in molten slag, it was found that the strength of bondage force between Pb²⁺ and the other cation was in the order of Si⁴⁺ > Fe²⁺ > Ca²⁺. Hence, it was considered that the repulsive force between Pb²⁺ and Fe²⁺ was lower than that between Pb²⁺ and Ca²⁺, which led to a smaller effect of FeO than CaO on volatilization of PbO from CaO–SiO₂–Al₂O₃–FeO molten slag.

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Biomass utilization is one of the most important methods for global warming mitigation from the viewpoints of both carbon sequestration and carbon-neutral energy use. Carbon sequestration potential should result from phytomass stock expansion, and in this study, the potential of phytomass stock expansion due to afforestation/rehabilitation with additional special water management was estimated by using several sets of global geographical information systems (GIS) data. The estimation was conducted under unified conditions for all the world areas by using a computer program based on the GIS data. The carbon sequestration potential of a land area was assumed to be primarily determined by its precipitation level if the area satisfied certain meteorological and geographical conditions for phytomass stock expansion, such as land use, temperature, slope, and soil type, and the sensitivities of these conditions were studied. The carbon sequestration potential due to regular afforestation/rehabilitation was estimated to be about 169 GtC in the world, and the effective regions for carbon sequestration were Brazil, etc. On the other hand, the increase in the carbon sequestration potential due to the additional special water management was estimated to be about 21 GtC in the world, and the effective regions were Saudi Arabia, west Australia, etc.

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Ultrasound irradiation and simultaneous gas bubbling into an aqueous solution of methylene blue has been studied in order to establish a cost-effective process for wastewater treatment. Various gases such as rare gases, oxygen, nitrogen, and carbon dioxide, as well as mixtures of argon and other gases have been used. The argon–oxygen mixture (70 : 30% v/v) gave the maximum degradation rate of ca. 45% after 30 min of treatment, and this was around 10% higher than that obtained with pure argon bubbling. Furthermore, the influence of the addition of a variety of metal oxide particles, including SiO₂, TiO₂, and Al₂O₃, has been examined. The degradation rate increased by 10%, to ca. 54%, by the addition of 2 g/L alumina for a treatment time of 30 min.

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Lignophenol-based adsorbents were prepared from rice and wheat straws and further modified by immobilization of dimethylamine groups. The adsorption behavior of the substrates for various metal ions in hydrochloric acid solution was studied. The lignophenol adsorbents selectively adsorbed Au(III) over the entire range of hydrochloric acid concentrations tested but showed no affinity for base metal ions. Adsorption of Au(III), Pd(II), and Pt(IV) on the dimethylamine-modified adsorbents was also unaffected by the presence of base metal ions. The highest loading capacity was observed for Au(III) in the case of all adsorbents; this could be primarily explained by the facile reduction of Au(III) to Au(0). The electrostatic interactions between protonated amine groups and anionic chloro complexes of Pd(II) and Pt(IV) in acidic chloride media was proposed as the main adsorption mechanism.

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An afforestation field experiment studying Eucalyptus camaldulensis, E. torquata, and Casuarina obesa with five different irrigation intervals was set up in an arid region in Western Australia. The irrigation intervals used were 2 weeks, 1 month, 3 months, 6 months, and no irrigation, which resulted in water supplies of 1243, 895, 511, 423, and 313 mm/y averaged over the experimental period, respectively. The average growth rates of C. obesa in sections with 2-week and 1-month irrigation intervals were 1.9 and 1.3 kg/(m²·y), respectively, about double those of E. camaldulensis. However, the average growth rate of C. obesa was lower than E. camaldulensis in sections with less irrigation. For C. obesa, water use efficiency was highest with a 2-week irrigation interval and quickly decreased with decreasing water supply. For E. camaldulensis, it was highest with a 1-month irrigation interval and did not decrease as much as that of C. obesa with decreasing water supply. We concluded that C. obesa has a high water use efficiency with a water supply more than 890 mm/y. E. camaldulensis, however, can grow more efficiently than C. obesa when the water supply is less than 510 mm/y. E. torquata is unsuitable for arid land afforestation.

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This study aims to clarify the material and energy flows in a well-known sewage sludge treatment plant in Japan; the treatment processes include composting, drying, incineration, and incineration with ash melting. We used not only statistical data but also data such as carbon, nitrogen, and moisture content in sludge obtained through our on-site observations. Material and energy flow analysis of sewage sludge composting is seldom reported in comparison with the analysis of other recycling and treatment methods. Therefore, we have performed material and energy flow analysis on sewage sludge composting to estimate factors such as environmental load and energy balance. We investigate the energy consumption of sewage sludge composting in one company that produces manure through aerobic fermentation of sewage sludge. In addition, we compare sewage sludge composting with incineration and evaluate their respective characteristics regarding sewage treatment and production of manure. It has been found that the use of anaerobic digestion of sewage sludge can reduce the overall energy consumption in sewage sludge treatment if power generation using biogas is adopted; however, the digestion of sewage sludge lowers the heating value of the digested sludge, requiring more energy to operate the digester. The energy consumption in a wastewater treatment plant accepting returned water from sludge digestion was increased by 10% to 20% compared to the process without sludge digestion. The overall energy consumption in both wastewater treatment and sludge digestion should be considered. The electric power was 60% of the overall energy consumption and 70% of the energy consumption in the plant's production sector.

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A novel, green method for hydrogen (H₂) production was studied; the method involves the mechanical mixing of aluminum (Al) with water (H₂O). We examined the use of glass and stainless steel reactors. When the glass reactor was used, the induction period of the reaction of Al with H₂O was long. The induction period decreased remarkably upon increasing the revolution rate; the optimal revolution rate was 1250 rpm. Furthermore, the reaction of Al with H₂O in the stainless steel reactor was examined to investigate the practical feasibility of this H₂ production method. In this case too an induction period was observed, and the induction period decreased upon increasing the reaction temperature and Al weight.

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The aim of this research is to investigate a hydrogen production system using low concentration of ethanol derived from biomass fermentation-renewable materials. By using a non-equilibrium box reactor containing CO₂ absorption agent and alumite catalyst in plate type, CO₂ and CO can be removed from the reaction field, without CO converting and dividing reactors. Due to insertion of CO₂ absorbent, it helped to build up hydrogen selectivity and decrease carbon monoxide formation. First, the support method of the alumite catalysts is studied to increase the durability of the catalysts and prevent carbon formation. The durability of the CO₂ absorption agent is also studied to improve the use times and prevent abrasion phenomenon. Then, the amount of hydrogen that is needed to feed in the 1 kW class household fuel cell is assumed. From these conditions, the required catalysts and CO₂ absorbent are computed. Subsequently, a box reactor is designed in order to appropriately introduce these plates, from which calculation of the reactor volume is performed.

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A shallow saline water solar pond is theoretically modeled and experimentally investigated using a carboxymethyl cellulose gel layer as an evaporation suppressor. Saline water shallow solar ponds are quite frequently encountered in deserts/arid areas and are considered potentially harmful to the soil, with no known usefulness. The influences of various parameters on the efficiency of the ground shallow solar pond are also investigated theoretically and experimentally. The present investigation shows that a very thin layer of gel is capable of increasing the thermal energy retaining capacity of the ponds, which can be harnessed by several available technologies.

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Poly(methylphenylsilane)–poly(benzylmethacrylate) (PMPS–PBzMA) block copolymer, a photobleachable polymer material for optical waveguide fabrication, was prepared by photopolymerization. A model has been formulated to predict the kinetic variation of carbon blocks and silicon blocks along the chain during photoinitiated radical vinyl polymerization of benzyl methacrylate (BzMA) using poly(methylphenylsilane) (PMPS). In the model, photodegradation of PMPS is assumed to be a first-order reaction, and other external conditions are treated as factors affecting the propagation and decomposition rate constants of PMPS. From curve-fitting, the model predicts 1) the decomposition rate constant of PMPS k_d, and the rate constant k, 2) the temporal variation of the average number of carbon atoms per structural block (L_C), and 3) the temporal variation of the average number of silicon atoms per structural block (L_Si). The rationale of the model is confirmed by prediction of the refractive index of the resultant copolymer. Furthermore, the effects of change in the UV intensity are evaluated.

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