Shigeyoshi Imaizumi

Cd(II) adsorption on various adsorbents obtained from charred biomaterials.

Cadmium could cause severe toxicant impact to living beings and is especially mobile in the environment. Biomass is abundant and effective to adsorb heavy metals, but is easy to be decomposed biologically which affects the reliability of long-run application. Several biomasses were charred with and without additives at temperatures less than 200°C in this study. The prepared adsorbents were further testified to remove Cd(II) from aqueous solution. Equilibrium and kinetic studies were performed in batch conditions. The effect of several experimental parameters on the cadmium adsorption kinetics namely: contact time, initial cadmium concentration, sorbent dose, initial pH of solution and ionic strength was evaluated. Kinetic study confirmed (1) the rapid adsorption of Cd(II) on GC within 10 min and (2) the following gradual intraparticle diffusion inwards the sorbent at neutral pH and outwards at strong acidic solution. The grass char (GC) was selected for further test according to its high adsorption capacity (115.8 mg g(-1)) and affinity (Langmuir type isotherm). The Cd(II) removal efficiency was increased with increasing solution pH while the highest achieved at sorbent dosage 10.0 g L(-1). The ionic strength affects the sorption of Cd(II) on GC to a limited extent whereas calcium resulted in larger competition to the sorption sites than potassium. Spectroscopic investigation revealed the adsorption mechanisms between Cd(II) and surface functional groups involving amine, carboxyl and iron oxide. The long-term stability of the pyrolyzed grass char and the potential application in engineering practices were discussed.

Woods Charred at Low Temperatures and Their Modification for the Adsorption of Cr(VI) Ions from Aqueous Solution

Despite being prepared at higher temperatures and involving greater energy consumption, activated carbons always show a smaller capacity and affinity towards the adsorption of Cr(VI) ions. After a brief review regarding Cr(VI) ion contamination and treatment, the preparation of a novel biosorbent from pyrolyzed wood char for Cr(VI) ion adsorption is described. Pyrolysis was conducted at temperatures within the range 200–350 °C, thereby helping to protect beneficial functional groups, saving energy and hence reducing costs. The influence of pH, concentration, adsorbent dosage, ionic strength and equilibration time on Cr(VI) ion adsorption by this biosorbent was investigated. It was shown that the char obtained at 200 °C possessed the highest Cr(VI) ion retention capacity (31.96 mg/g) but required the longest equilibration time (> 47 d). Coating the char with nano-scale iron oxide greatly improved its adsorption affinity towards Cr(VI) ions, with a higher adsorption affinity (Henrys law Kd = 2.988 ℓ/mg) and an enhanced Cr(VI) ion adsorption capacity (53.45 mg/g) being accomplished within a much shorter equilibration time (24 h). Spectroscopic studies confirmed that complexation of Cr(VI) ions occurred via surface hydroxy groups. The methods proposed for preparing and modifying wood char are likely to be applicable in industrial wastewater treatment.

Erratum for "Woods Charred at Low Temperatures and Their Modification for the Adsorption of Cr(VI) Ions from Aqueous Solution" by Zhenze Li, Takeshi Katsumi, Toru Inui and Shigeyoshi Imaizumi

Zhenze Li1,*, Takeshi Katsumi1, Toru Inui1, Shigeyoshi Imaizumi2, (1) GSGES, Kyoto University, Sakyo, Kyoto 606-8501, Japan., (2) Department of Advanced Interdisciplinary Science, Utsunomiya University, Yoto, Utsunomiya 321-8585, Japan. Adsorption Science & Technology (2010) Vol. 28, No. 5, pp. 419–435. DOI: 10.1260/0263-6174.28.5.419 On page 433, Table 3 should be as follows: TABLE 3. Adsorption Capacities and Affinities of Various Adsorbents Adsorbent Adsorption capacity (mg g−1) Adsorption affinity (l mg−1) Reference Aerobic granules functionalized with polyethylenimine 401.5 7.6 ∞ 10−3 Sun et al. (2010) Amino-functionalized mesoporous silica 109.6 4.4 ∞ 10−3 Li et al. (2008) Sawdust-activated carbon 44.0 0.2215 Karthikeyan et al. (2005) Layered double hydroxides 31.2 2.7 ∞ 10−4 Das et al. (2004) Humic acid extracted from coal 20.8 – Arslan et al. (2010) Carbon nano-tube 20.56 – Di et al. (2004) Granular activated carbon 7.0 – Di Natale et al. (2007) Magnetic Fe3O4 nano- particles 2.95 – Begum and Anantharaman (2009) Bentonite 0.052 – Khan et al. (1995) Wood char (200 °C) 31.96 1.45 ∞ 10−2 This study Ferric-laden char 53.45 1.3 ∞ 10−3 This study

Mechanical and Chemical Properties of Ash Molten Slag Mixed With Bentonite

Since 2000, the number of facilities to produce the ash molten slag has rapidly increased in Japan. But, the place where the ash molten slag is used as construction material is limited such a municipality as ash molten slag facility is located. So, it is necessary to establish effective uses other than aggregate in base course of a road or as aggregate in ready mixed concrete for building, etc.

Model Tests On Deformation Behavior of Bentonite Mixed Soil Layer Subjected to A Local Subsidence In Landfill

Compacted soil mixed with bentonite having a low hydraulic conductivity of less than 10-6 cm/s is commonly used as barrier layer in waste landfill in Japan. But it is afraid that the bentonite mixed soil may have cracks when the base ground experiences a local subsidence. The authors conducted trap door tests of bentonite mixed soil under a surcharge pressure of 107.8kN/m2. The sizes of the compacted soil layer mixed with 10 % bentonite are 800 mm in length, 200 mm in width and 100 or 200 mm in thickness. The width of trap door was changed as 30, 40 and 50 cm. The rate of lowering the door was 1.0 mm/day. It was found that bentonite mixed soil had a crack in the middle height of soil layer when the trap door subsided between 12 and 13 mm. And then the crack reached at top and bottom surfaces when the door was lowered between 13 and 27 mm. Therefore the shear crack is predominant than bending crack. In the study the image analysis for the tests with a lowering rate of 0.5 mm/min was also conducted by recording the deformation on the video. The amount of calculated shear strain at the cracked position was lager than 20%.

Experimental Study on Thermal Strain Creating in Barrier Sheet in Waste Landfill

Many types of barrier sheets are widely used in waste landfill in Japan. But these materials have high values of coefficient of thermal expansion comparing with other construction materials. This causes thermal stress in the barrier sheet when the circumstance temperature changes. Sometimes, it brings to serious problem such as tearing of sheet or failure of anchorage. So, it is very important to know how much the strain/stress is created due to the change of circumstance temperature. The authors constructed large model landfill site surrounding a bank with a height of 5m, and whole area of 1,600 m2. Many types of barrier sheets, HDPE, LDPE, TPU and TPO were placed on the slope. Strain gages were pasted on the surface of the barrier sheets. Thermo-couples were also pasted to measure temperature of the barrier sheets. These data were automatically stored into the data-logger. Measurements were conducted for 2 years off and on. Measured strain level changed corresponding to the change of the temperature. The relationship between the temperature and the strain level of each barrier sheet were obtained. It is also measured in the corner and near the concrete structure. And it is found that strains are created isotropic even in the corner of the model landfill site.

Durability Evaluation of Geomembrane Liners Using an Indoor Accelerated Exposure Experiment and an Outdoor Exposure Experiment for 10 years: Effects on Durability of the Protective Covering

本研究は, 遮水シートの耐久性評価を目的とし, 室内促進暴露実験と実暴露実験を実施し, 遮水シートの力学特性 (硬さ, 引張強さ, 伸び率) や表面状態の変化を追跡評価したものである。室内促進暴露実験の結果, 伸び率は経過時間とともに徐々に低下し5, 000時間では初期値のおおむね80%程度となり, そのとき遮水シート表面には亀甲状の微小亀裂が発生していることが確認された。一方10年間の実暴露実験を行った遮水シートの力学特性の変化は小さく, ある種類の遮水シート表面には室内促進暴露実験と同様の亀甲状の微小亀裂が観察されたが, 最終処分場の標準的な供用期間である15年に対して遮水シートの耐久性は充分余力あるものと推測された。また両実験結果を比較検討した結果, 2, 000時間強の室内促進暴露実験の結果が実暴露実験10年間に相当することが確認された。さらに遮光性保護材を用いると, 遮水シートの劣化の主要因とされる紫外線を遮断することができ, 遮水シートの耐久性が大幅に向上することも確認できた。