Hiroaki Habaki’s research while affiliated with Tokyo Institute of Technology and other places

To separate both copper and 2,2',2'',2'''-(ethane-1,2-diyldinitrilo)tetraacetic acid (EDTA) from the waste electroless copper plating solution by solvent extraction, the liquid–liquid equilibria of the copper-EDTA complex and unbound EDTA ion were experimentally measured. An organic solution of tri-n-octylmethylammonium chloride (TOMACl) was used as solvent. The kerosene solution of TOMACl could extract both copper-EDTA complexes and EDTA ions from the model wastewater. The fractional removal and distribution ratios of both the copper-EDTA complex and EDTA ions decreased as the pH increased. The valence number of the major copper-EDTA complex or EDTA ion in the aqueous phase increased with pH, and the number of TOMA⁺ cations required to chelate the complexes and ions increased. These complexes and ions had lower reactivity with TOMACl owing to steric hindrance. These effects caused lower removal of both copper and EDTA in a higher pH range, which is a typical condition of waste electroless copper solution.

Duckweed (Lemna aoukikusa), a common aquatic plant found worldwide, was used to treat a solution polluted with the model antibiotics, ciprofloxacin (fluoroquinolone group) and sulfamethoxazole (sulfonamide group), which were selected because they were frequently present in pharmaceutical wastewater. The plant could grow even in an aqueous solution with a high concentration of both antibiotics, and illumination enhanced its growth. The presence of antibiotics in the solution inhibited the growth, and the inhibitory effect of sulfamethoxazole was greater than that of ciprofloxacin. Ciprofloxacin was effectively reduced by hydrolysis, photolysis, and uptake by the duckweed. Although sulfamethoxazole was resistant to hydrolysis and photolysis, its uptake by duckweed under illumination conditions could remove both antibiotics from the solution, even at high concentrations. Regarding the contribution of the respective types of antibiotic removal rates to total antibiotic removal, the uptake rate of antibiotics was the highest, and the treatment of wastewater using duckweed was proposed as a promising treatment method.

The main aim of this study is to remove lignin, which is one of the main colored substance in palm oil mill effluent (POME), by adsorption using activated carbon prepared from palm kernel shell (PKSAC) for POME decolorization in Thailand’s palm industry. First, PKSAC was prepared by a chemical activation method using orthophosphoric acid and the effects of treatment conditions on yield and characteristic of PKSAC were studied. With lower treatment temperature, the yield and specific surface area of PKSAC became higher, and PKSAC with high yield (0.8 at highest) and surface area (1,400×10³ m² kg-AC⁻¹ at highest) could be obtained without extreme elevation of treatment temperature. Second, batch equilibrium adsorption of the model POME containing lignin was conducted using the prepared PKSAC to study the adsorption performance of PKSAC. The obtained PKSAC could effectively adsorb and remove lignin in model POME (fractional removal of 0.4 at highest). The adsorption followed the Langmuir equation and the saturated adsorbed amount was correlated with the specific surface area of PKSAC. Subsequently, the feasibility of PKSAC utilization for POME treatment was discussed by a simple material balance in the palm oil production process based on the yield and adsorption performance of PKSAC obtained in the above experiments. The amount of obtained PKSAC was much larger than that necessary for the removal of all lignin in POME in the process. Consequently, the treatment of POME by PKSAC was proposed as a feasible method to remove lignin for POME decolorization in Thailand’s palm industry.

Issues related to food wastage have become a significant threat to sustainable development, particularly in developing countries. Cooked rice, reported as one of the abundant regional food wastes, is a...

The main aim of this study is to treat palm oil mill effluent (POME) containing phenol, which is a hazardous compound, using activated carbon (AC) prepared from palm kernel shell (PKS), one of the byproducts of the palm oil industry. First, PKS from Thailand was characterized by proximate, elemental, and thermogravimetric analyses. The high carbon and low ash contents in the PKS indicated that PKS is a promising precursor for producing AC. Then, palm kernel shell activated carbon (PKSAC) was prepared using chemical activation with orthophosphoric acid as an activating reagent under various conditions. The physical and chemical properties of the PKSACs were characterized using nitrogen adsorption–desorption and Fourier-transform infrared spectroscopy (FT-IR), respectively. Chemical activation improved the yield and physical properties, even as it changed the chemical properties of PKSACs. The PKSACs thus prepared contained large volumes of micropores. Using the prepared PKSACs, batch equilibrium adsorption was conducted to remove phenol from the POME model. The PKSACs could successfully adsorb and remove phenol from the POME model. The phenol adsorption followed the Langmuir model, and the saturated adsorbed amount of phenol increased with increase in surface area. Based on these results, it is concluded that the treatment of POME using PKSACs produced by chemical activation would be a practicable treatment method since the prepared PKSACs provide a high yield and are capable of treating model hazardous compound in POME.

In Asia, uneaten cooked rice is the highest portion amongst many forms of food wastes that are thrown away. In order to make use of the thrown-away rice and potentially use it for liquid fuels, steamed Japanese rice was evaluated on biobutanol production through a two-step fermentation by amylase-producing Aspergillus oryzae, and solvent-producing Clostridium acetobutylicum YM1. The effects of sterilization and providing anaerobic conditions on solvent production in acetone-butanol-ethanol (ABE) fermentation cannot be underestimated. Several conditions, including aerobic, anaerobic, sterile, and non-sterile were investigated concerning the solvent production capability of Clostridium acetobutylicum YM1. The maximum solvent production was 11.02 ± 0.22 g/l butanol and 18.03 ± 0.34 g/l total ABE from 75 g/l dried rice. The results confirmed that the solvent production performance of the YM1 strain was not affected by the sterilization conditions. In particular, 10.91 ± 0.16 g/l butanol and 16.68 ± 0.22 g/l ABE were produced under non-sterile and aerobic conditions, which can reduce industrial-scale production costs.

To improve biodiesel production from jatropha, its shell, a waste material, was thermally treated to produce activated carbon (AC) and the AC was applied to purification of glycerol from transesterification. The AC was prepared by chemical activation method using H3PO4 as the activation agent. The yield of the chemically activated carbon was better than the physically activated carbon in the higher range of thermal treatment temperature, and the prepared AC had a sufficient specific surface area. For purification of the glycerol obtained from transesterification to remove impurities such as methanol and monoolein, the AC was also used for measuring the adsorption equilibria with the model glycerol solutions containing impurities, and adsorption isotherms of these compounds were prepared. The AC could absorb and remove the impurities in the model glycerol phase. The adsorption of the impurities was enhanced by chemical activation because of a larger specific surface area, and the effects of surface modification by the activation were inefficient for the adsorption. A rough process assessment suggested that the amount of AC prepared from the shell was sufficient to purify glycerol.

For the separation of petroleum-derived heavy fractions by solvent extraction, the liquid-liquid equilibrium extraction of model heavy fractions, binary and multicomponent model oils, with aqueous methanol solutions was measured, and the effects of nitrogen heterocyclic and other coexisting compounds on the equilibrium extraction were studied. The distribution coefficient increased in the following order of the group compounds; alkanes, aromatics and heterocyclic compounds when the carbon numbers in the molecules of interest were same, and it decreased with an increase in the carbon number of the compound among the respective groups. The coefficients for indoles and quinolines were comparable, and those of carbazoles were smaller. The liquid-liquid equilibrium of nitrogen heterocyclic compounds with the multicomponent system was similar with that with the binary system, and the approximate trend of liquid-liquid equilibrium in the multicomponent system could be evaluated based on the results of simpler systems.

Methods for obtaining high-concentration (ca. 40 g/L) ethanol from cassava stem (CS) were explored by investigating the effects of acid hydrolysis conditions, hydrolysate concentration, and intermittent inoculation of yeast on ethanol fermentation. Two-step acid hydrolysis demonstrated that a reduction in autoclaving temperature from 121 °C to 111 °C remarkably lowered the furfural concentration in the hydrolysate, with only ± 10% differences in the glucose and xylose concentrations. For the concentration of sugars in the CS hydrolysate, the acid hydrolysate prepared with CS concentration of 200 g/L was used instead of distilled water for the second step of acid hydrolysis using new CS biomass (i.e., two-times acid hydrolysis). This produced a concentrated hydrolysate containing 95 g/L of glucose and 0.95 g/L furfural. Saccharomyces cerevisiae strain IAM 4178 was inoculated into the concentrated CS hydrolysate after verifying its furfural tolerance. Furfural was rapidly degraded and glucose was converted to ethanol during the startup period, whereas cell density decreased to approximately 10% of the initial value and ethanol production ceased by 72 h. IAM 4178 was then re-inoculated intermittently to maintain the cell density at 10 8 cells/mL, which eventually resulted in the complete uptake of glucose and the production of high concentrations of ethanol, up to 37.5 g/L.

To improve the versatility of light cycle oil (LCO), separation of aromatic compounds from LCO by solvent extraction was investigated. LCO was analyzed to identify 35 components: 19 aromatics and 16 alkanes. The batch liquid–liquid equilibrium extraction of LCO was performed using furfural, sulfolane, and methanol as extraction solvents. In each solvent, the aromatics present in LCO were selectively extracted relative to the alkanes. The separation selectivities of aromatics relative to alkanes were larger in sulfolane than in the other solvents. Among the aromatic components, di- and tricyclic compounds were selectively extracted relative to the monocyclic ones.