Takeshi Kajimoto

Removal of mercury and other metals by carbonized wood powder from aqueous solutions of their salts

Sugi (Cryptomeria japonica D. Don) wood powder was carbonized at varying temperatures and used as a material to remove heavy metals from their aqueous solutions. Single solutions of mercuric chloride and mixed aqueous solutions containing lead nitrate, arsenic chloride, and cadmium chloride as well as mercuric chloride (1, 5, and 10 ppm) were prepared to determine the efficiency of removing heavy metals by these materials. Wood powder and carbonized wood at 200°, 600°, and 1000°C removed mercury within the concentration range 1–10ppm; mercury was preferentially removed even when mixed with other heavy metals. Wood powder carbonized at 1000°C achieved the best removal of heavy metals among the wood-based materials and even commercial activated carbon in both single and mixed solutions.

Characteristics of a bioxalate chelating extraction process for removal of chromium, copper and arsenic from treated wood

The disposal of wood waste treated with chromated copper arsenate (CCA) is a problem in many countries. We have proposed a novel chelating extraction technique for CCA-treated wood using bioxalate, a solution of oxalic acid containing sufficient sodium hydroxide to adjust the pH to 3.2, which is an effective way to obtain an extraction efficiency of 90% for chromium, copper, and arsenic. The purpose of the present study was to investigate the characteristics of bioxalate extraction of CCA-treated wood. Extractions of CCA-treated western hemlock chips with solutions of bioxalate, oxalic acid, and sodium hydroxide were carried out. The use of bioxalate was confirmed as the most effective extraction technique for chromium, copper and arsenic, with an efficiency of 90%. Extraction with simple oxalic acid was ineffective for copper (less than 40% extraction efficiency), but effective for chromium and arsenic, with 90% efficiency. Sodium hydroxide showed a similar tendency, being ineffective for chromium and copper (less than 20% extraction efficiency), but relatively effective for arsenic (around 70-80% efficiency). We also discovered an interesting phenomenon whereby the addition of sodium hydroxide to a simple oxalic acid solution during the oxalic acid extraction progress resulted in dramatically increased extraction efficiency for copper, chromium and arsenic, up to 90%. Although oxalic acid was ineffective for copper extraction, the addition of sodium hydroxide during the oxalic acid extraction process rendered it effective.

Improving fire retardancy of fast growing wood by coating with fire retardant and surface densification

Fire retardant fast-growing wood product was developed by coating with fire retardant and densifying the surface of wood. Trimethylol melamineformaldehyde resin mixed with phosphoric acid was coated on the wood surface, preheated and followed by hot pressing. Effects of the amount of coating, preheating temperature, and densifying ratio on the fire retardancy of sugi (Cryptomeria japonica D. Don) wood, and pressing temperature and pressing time on that of albizia (Paraserianthes falcataria Becker) wood were discussed. Bending strength, creep performance under fire and fire retardancy were evaluated. The results showed that the treatments improved the fire retardancy of woods without reduction in the bending strength.

Capturing the arsenic fraction of CCA treated waste wood in the solid instead of in the gas phase during pyrolysis

Recycling of preservative‐treated waste wood can be an environmental problem due to toxic elements being emitted into the environment. Pyrolyzing CCA‐treated wood at low temperature without any oxidizing agent is applied to capture the arsenic fraction in the solid residue. The influence of well‐defined process parameters such as pyrolysis temperature, time and heating rate are studied. Arsenic contents in the gas phase were measured by a wet chemical method while structural analysis of the arsenic reaction products was determined with Transmission Electron Microscopy.

Resistance of Silicon-Containing Carbonized Lignin to Atomic Oxygen Erosion

Spacecraft in low Earth orbit (LEO) are exposed to atomic oxygen (AO). It is thus important to develop an environmentally friendly material that can be applied to the outer surfaces of spacecraft in LEO to protect them against AO. Carbonized material containing electroconductive graphitic microlayers is promising for this purpose. We produced carbonized lignin (CW) by separating wood in L-lactic acid and we investigated the AO erosion resistances of CW and CW containing Si. X-ray photoelectron spectroscopy (XPS) revealed that the O/C ratio increased on AO exposure. The CW sample without Si and CW samples containing 20% and 40% Si exhibited less erosion than CW samples containing 5% and 10% Si. XPS revealed that the presence of Si resulted in the formation of SiO2 on the sample surface. For CW with Si contents of 20% and 40%, the SiO2 coverage may be sufficiently large to prevent attack by AO.

Wood-Based, Diamond-Like Carbon for Improved Resistance Against Atomic Oxygen

Polyimide or fluorine polymer that are used as heat-control materials on structures in LEO and GEO orbits, if not protected from the atomic oxygen (AO) may be severely degraded by the formation of microcracks. Carbonized materials are suitable for use in low Earth orbit (LEO) as they have excellent mechanical strength, electrical insulation, and thermal conductivity. Carbonized wood, in the form of a Japanese lacquer composed of aromatic compounds derived from the urushi tree, could potentially be used as the outer surface material of spacecraft, provided however that its resistance against AO irradiation in LEO is sufficient. The main aim of this study, therefore, is to develop the requisite technology to impart erosion resistance against AO to the carbonized wood. Specifically, increased sp2 bonding in the Si-doped diamond-like carbon introduced here is shown providing effective resistance against AO-induced erosion.