One of the primary sources of drinking water and for non-potable applications is saline (sea) water. Conversely, a vast amount of wastewater is currently produced that needs to be treated before using or discharging. Ocean sea water is considered to be a raw material used in the desalination process and converted to usable water. In the initial stage of the study, a microbial fuel cell (MFC) with a cation exchange membrane (CEM) and an anion exchange membrane (AEM) were used as separators, in the experiments under different (1, 10, 100 and 1000 Ω) loads of resistance, to measure the efficiency in wastewater treatment and electricity production. The system using a CEM produced the maximum or optimal current of 1.8 mA, a columbic efficiency (CE) of 42% and 80% of chemical oxygen demand (COD) removal at 1 Ω external resistance. While the system running with an AEM achieved a maximum current of 1.8 mA, 40% CE and 77% COD removal at 1 Ω. It highlighted the minimal difference between the performances of the MFC either by using an AEM or CEM. In the second stage of this study, a microbial desalination cell (MDC) used as a novel bioelectrochemical system, was developed by modifying the enriched and optimised MFC system. The MDC was investigated for the desalination of salt water and wastewater treatment. The performance of the MDC with 10 g/l of NaCl salt was measured for desalination of brackish water and COD removal for wastewater treatment, CE and electrical current production. The COD removal of the system was greater than 80%, and the percentage of desalination was 100% after running for five days. The MDC system produced a maximum current of 1.3 mA. Therefore, the results from the study confirmed that the MDC was an appropriate technology used for simultaneous desalination and wastewater treatment applications and facilitating the production of green energy.
We investigated alginate oligosaccharide (AOS) as a simple growth promoter of Spirulina. The maximum growth promotion effect of 1,000 ppm AOS was 3.68-fold higher than that of control at 8 days of batch culture. Biomass productivity and contents of metabolites, such as phycocyanin and protein, increased with repeated batch feeding of AOS. Highest biomass productivity of 168 mg L−1d−1 was obtained at the third stage of repeated batch culture.
Metal air battery attracts attention as an automobile battery, because of its high energy density. In order to reuse the battery, it is necessary to undertake reduction of metal oxide which is generated at the cathode without large environment load. We conducted the reduction of ZnO powder by radio-frequency dielectric heating. The ZnO powder and a reducing agent of organic liquid is put into a reaction vessel, and the tip of the electrode inserted from the top of the vessel is in contact with the surface of the powder. By measuring the spectrum of the blackbody radiation, the temperature was found to be approximately 2000 K. The reduction amount of ZnO increased remarkably when 0.7 to 1.4 mL of methanol was added as a reduction agent to 2.0 g ZnO powder, with a maximum of 27.6 mg at 1.1 mL reached. The reduction amount was smaller when ethanol, acetone, furfural, cyclohexane or dodecane were added as a reduction agent. The maximum energy efficiency is 3.3% without taking the reaction energy of the reduction agent into consideration, whereas it becomes 1.0% when taking it into consideration.
Oxy-tetracycline (OTC) has been recognized as not only a good antibiotic but also environmental contamination resulted from over-dosage and leakage from agricultural activities. Among various alternatives, catalytic ozonation is a promising method because of its simplicity and effectiveness. In this work, magnetic carbon nanoparticles (M-CNPs) synthesized by nebulizing pyrolysis of glycerol and ferrocene has been applied as a catalyst for enhancing ozonation of OTC. Effects of catalyst loading and initial concentration of tetracycline on degradation of oxy-tetracycline have been experimentally examined in comparison with other typical carbonaceous powders which are carbon black and graphite. While the change of OTC concentration were analyzed using high performance liquid chromatography (HPLC) analyzer for examining its characteristics, fresh and spent carbonaceous catalysts were also characterized using electron microscopy, surface area and porosity analyzer, and x-ray diffraction (XRD) analyzer.It was found that M-CNPs could exhibit a superior performance in the removal of OTC by adsorption and catalytic ozonation, resulting a faster completion of OTC removal within 30 min or 2 times faster when compared with the cases of carbon black and graphite powder as well as ozonation alone.
The flame emission spectra were measured from the combustion of biomass in a boiler, from which the ratio of the alkali metals’ number densities (sodium and potassium) were precursory derived. Fly and bottom ash samples were collected to determine their composition via scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). A comparison of the alkali metals’ number density ratios (from the flame emission spectra) and the ash composition provided information on potential pathways for the alkali metals. The comparison also showed that the number density ratio can be taken as a tentative in-situ indicator of the alkali metals’ ratio. The ash composition also allowed the determination of several slagging and fouling indices.
Promotion of growth and lipid productivities of freshwater microalga Botryococcus braunii by steel slags: steelmaking slag (SMS) and blast furnace slag (BFS) was investigated. Addition of SMS by 5 g L-1 brought promotion effects of growth and lipid productivities by 1.74 and 2.16-fold, respectively, higher than control. In case of applying BFS by 5 g L-1, similar promotion effects of growth and lipid productivities by 2.39 and 4.47-fold, respectively, higher than control achieved. Both the biomass and lipid productivities of B. braunii were enhanced by elution of iron from SMS and other components from BFS. Interestingly, BFS were more effective than SMS regarding to the productivities of metabolites.
Ionic liquids (ILs) pretreatment has emerged as the promising technology toward environmentally benign conversion of lignocellulosic residues into high value cellulosic fiber as sustainable raw material for biocomposite manufacturing. In this work, the impact of an ionic liquid (IL) 1-ethyl-3-methylimidazolium diethylphosphate ([emim] [dep]) pretreatment of oil palm frond (OPF) on the flexural properties of the composite board has been reported. Ionic liquid pretreatment of OPF fiber under high solids loading (IL/biomass ratio = 1.0) was conducted prior to compounding with thermoplastic starch which was used as binder polymer. Effect of IL pretreatment on OPF fiber was assessed by employing Fourier Transform Infrared Spectroscopy technique. IL treated composite board was found to exhibit superior flexural properties than that of untreated board. Flexural strength was increased from 10 MPa for untreated composite to 12.75 MPa for composites fabricated from IL treated OPF particles.The obtained results evidenced that the IL pretreatment could be a promising, cost-efficient and benign approach for conversion of agricultural waste into high value engineered composite panels. The study plainly demonstrates that IL based pretreatment could be a green technology for effective utilization of lignocellulosic waste biomass in the biocomposite manufacturing.
Production of furfural from biomass has attracted many research interests due to its usefulness as important chemical solvent and chemical feedstock for value-added products. Conversion of D-xylose to furfural via dehydration reaction enhanced by heterogeneous catalyst has also been an interesting issue. In this work, singlewalled carbon nanohorns (CNHs) hybridized with metal nanoparticles were proposed for catalytic dehydration of D-xylose to furfural for the first time. CNHs hybridized with Ni and Cu nanoparticles were in-house prepared by Gas-inject arc-in-water (GI-AIW) and then used as a catalyst for D-xylose dehydration. Physical and chemical properties of the catalyst samples were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analyzer and BET analyzer. It is notable that Ni/CNHs provided the highest D-xylose conversion and furfural yield.
For highly effective pretreatment of biomass for the production of ethanol, a hydrothermal explosion system was developed. Eucalyptus was selected as a sample hardwood biomass. Temperature and holding time dependence were studied to determine optimum conditions.Hydrothermal explosion and hydrothermal slow cooling were compared to confirm the explosion effect. Hydrothermal explosion showed higher sugar yield than the hydrothermal slow-cooling process, and sugar yield was 70% under optimized conditions. Dependence on enzyme concentration was also examined.
Hence the development of this cultivation technology would contribute greatly to the progress of onshore cultivation for the production of biomass energy from macroalgae in the future. Recently, the demand of C. lentillifera is rapidly increasing, because it is utilized not only as food but also as functional ingredients. Therefore, a growth enhancement technology of algae using carbon dioxide (CO2) attracts attention as productivity improvement technology. Although it has been reported that the growth of C. lentillifera is facilitated when CO2 is added to culture seawater, the effects of environmental factors during cultivation has not been clarified. Accordingly, we investigated the influences of seawater temperature (20°C, 25°C, 28°C), photon flux density (75 μmol m-2 s-1, 125 μmol m-2 s-1, 250 μmol m-2 s-1) and photoperiod (12 L/12 D, 18 L/6 D, 24 L/0 L) on the growth of C. lentillifera cultivated in the highly concentrated CO2 seawater. As a result, it was possible to increase the growth rate of C. lentillifera by addition of CO2 under any conditions. This suggested that the use of the CO2-enriched seawater improved the decrease of the growth amount due to seawater temperature fluctuation and insufficient sunshine.
This study conducted the rough assessment on the model transporting liquid methane converted by methanation of carbon dioxide with hydrogen produced by water electrolysis using electric power of large scale wind power assumed to be installed in Patagonia region in Argentina from the viewpoint of energy productivity, energy balance, carbon dioxide circulation possibility and investment recovery. It was assumed that the CO2 for methanation was transported from both Japan where CO2 was produced by using the methane and South America. As a result, when wind turbines in 3000 kW class of 7.81×105 units were assumed to be installed, the amount of liquid methane which could be transported to Japan was 2.2 times as large as the import volume of LNG in Japan, indicating that the model had the adequate energy productivity. The energy loss of the model was 64.7%. The amount of carbon dioxide emission from liquid methane transported from Patagonia region to Japan was equal to 49.1% of the amount of carbon dioxide which was necessary for methanation in Patagonia region, which was short. Consequently, the CO2 which is short for methanation should be procured from the other system in South America. Since this assessment was carried out based on some bold assumptions, the further investigation should be necessary in the future.