Prasert Pavasant

Activated carbon from Eucalyptus camaldulensis Dehn bark using phosphoric acid activation.

The powdered activated carbon prepared by phosphoric acid activation was significantly affected by the carbonization temperature and the weight ratio between raw material and phosphoric acid. With an activation time of 1h and an impregnation ratio of 1:1, the activated carbons with better adsorption capacity were obtained at 500 degrees C. A reduction in the adsorption capacity of the carbon product at higher acid content than this was observed, possibly due to the collapse of the micropore structure. The properties of the resulting activated carbon were: bulk density 0.251gcm(-3), ash content 4.88%, yield 26.2%, iodine adsorption 1043mgg(-1), methylene blue adsorption number 427mgg(-1), and BET surface area 1239m2g(-1).

Batch studies of adsorption of copper and lead on activated carbon from Eucalyptus camaldulensis Dehn. bark

Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(II) and Pb(II). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(II) and Pb(II) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-second order model where equilibrium adsorption capacities and adsorption rate constants increased with initial heavy metal concentrations. The adsorption isotherm followed Langmuir better than Freundlich models within the temperature range (25-60 degrees C). The maximum adsorption capacities (qm) occurred at 60 degrees C, where qm for Cu(II) and Pb(II) were 0.85 and 0.89 mmol/g, respectively. The enthalpies of Cu(II) and Pb(II) adsorption were 43.26 and 58.77 kJ/mol, respectively. The positive enthalpy of adsorption indicated an endothermic nature of the adsorption.

Pressurized hot water extraction of anthraquinones from the roots of Morinda citrifolia

This study examines pressurized hot water extraction of anthraquinones from dried roots of Morinda citrifolia (Noni). The effects of various operating conditions such as water temperature (110, 170, and 220 °C), and water flow rate (2, 4, and 6 mL min−1) on extraction yield and extraction rate were determined. At 220 °C, the extraction yield was the highest and was approximately 43.6 mg g−1. Subcritical water extraction at 4 mL min−1 or higher was found to be able to recover all the antraquinones present in the roots within 3 h of extraction, even at 170 °C. Pressure had no significant effect on the results for the range of temperatures studied. The flow rate of 6 mL min−1 resulted in the highest extraction rate, but the extraction efficiency, as measured by the amount of anthraquinones extracted per unit volume of water was lower than that of 4 mL min−1. Anthraquinones solubility in pressurized hot water was determined. The results indicate a presence of a mass transfer limitation in the extraction process from solid matrix.

Bubble size distribution and gas–liquid mass transfer in airlift contactors

Abstract This work investigated the distribution of bubble size in annulus sparged airlift contactors (ALCs). Increasing gas velocity in the ALC considerably reduced the size of the bubble and shifted the distribution of bubble size from the normal to log-normal types. Bubble size was found to decrease along the axial distance in the riser of the ALC. Moreover, an increase in the ratio between the cross-sectional areas of the downcomer and riser was found to result in the decreasing bubble size at high superficial gas velocity. Spargers with a large number of orifices led to a larger bubble size in the system. In contrast, it was found that a comparatively broad bubble size distribution was caused by employing a gas sparger with less number of orifices. This work also examined the gas–liquid mass transfer characteristics of the ALC in forms of mass transfer coefficient and specific interfacial area which were individually evaluated. It was found that the specific interfacial area, rather than the mass transfer coefficient, played a more significant role in controlling the overall rate of mass transfer in the system.

Life cycle assessment of bagasse waste management options.

Bagasse is mostly utilized for steam and power production for domestic sugar mills. There have been a number of alternatives that could well be applied to manage bagasse, such as pulp production, conversion to biogas and electricity production. The selection of proper alternatives depends significantly on the appropriateness of the technology both from the technical and the environmental points of view. This work proposes a simple model based on the application of life cycle assessment (LCA) to evaluate the environmental impacts of various alternatives for dealing with bagasse waste. The environmental aspects of concern included global warming potential, acidification potential, eutrophication potential and photochemical oxidant creation. Four waste management scenarios for bagasse were evaluated: landfilling with utilization of landfill gas, anaerobic digestion with biogas production, incineration for power generation, and pulp production. In landfills, environmental impacts depended significantly on the biogas collection efficiency, whereas incineration of bagasse to electricity in the power plant showed better environmental performance than that of conventional low biogas collection efficiency landfills. Anaerobic digestion of bagasse in a control biogas reactor was superior to the other two energy generation options in all environmental aspects. Although the use of bagasse in pulp mills created relatively high environmental burdens, the results from the LCA revealed that other stages of the life cycle produced relatively small impacts and that this option might be the most environmentally benign alternative.

Flat panel airlift photobioreactors for cultivation of vegetative cells of microalga Haematococcus pluvialis

The novel flat panel airlift photobioreactor (FP-ALPBR) was proposed as an alternative system for the cultivation of Haematococcus pluvialis NIES-144. Changes in the efficiency of the system were tested in response to variations in two engineering parameters: the ratio between the downcomer and riser cross-sectional areas (A(d)/A(r)) and the size of the system (as determined by the length of the panel) and to one operating parameter: the superficial gas velocity (u(sg)). The best growth performance was obtained by operating the system at a superficial velocity of 0.4 cms(-1) and with a downcomer-to-riser cross-sectional area ratio of 0.4. The 17-l FP-ALPBR system was capable of giving reasonable growth characteristics with a maximum cell density of 4.1 x 10(5)cell ml(-1) and specific growth rate of 0.52 day(-1) being achieved. A similar level of performance was obtained from the 90-l FP-ALPBR system, i.e., cell density=40 x 10(4)cell ml(-1) but with a slight decrease in specific growth rate to 0.39 day(-1). The performances of these two differently sized FP-ALPBRs were compared with two conventional cylindrical airlift photobioreactors (C-ALPBRs) of different dimensions. The 90-l FP-ALPBR exhibited reasonably good performance when compared with the two 17-l systems (both C- and FP-ALPBRs); however, the best growth rate was observed using the 3-l C-ALPBR. Semi-continuous cultures, which could be periodically harvested at a reasonably high growth rate, were successfully created. Of all the systems investigated in this study, the 90-l FP-ALPBR was found to be the most cost-effective, as it could cultivate 18 g of alga for approximately US

Comparison of Extraction Methods for Recovery of Astaxanthin from Haematococcus pluvialis

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Production of protein-rich fungal biomass in an airlift bioreactor using vinasse as substrate

Solvent extraction, ultrasound assisted extraction (UAE), and microwave assisted extraction (MAE) were examined for the extraction of astaxanthin from Haematococcus pluvialis. In all cases, acetone was found to give the highest astaxanthin recovery compared with other selected solvents, i.e., methanol, ethanol, and acetonitrile. Among the various methods, MAE at 75°C for 5 min resulted in the highest astaxanthin recovery (74 ± 4%).

Microwave pretreatment of defatted rice bran for enhanced recovery of total phenolic compounds extracted by subcritical water

The potential for large-scale production of an edible fungus, Rhizopus oligosporus, on a liquid residue from sugar-to-ethanol production, vinasse, was investigated. An airlift bioreactor (2.5-L working volume) was used for cultivating the fungus on 75% (v/v) vinasse with nutrient supplementation (nitrogen and phosphorus) at 37°C and pH 5.0. Aeration rates were varied from 0.5, 1.0, 1.5 to 2.0 volume(air)/volume(liquid)/min (vvm). The fungal biomass yield depended on the aeration rate, and the highest fungal biomass obtained was 8.04±0.80 (g(biomass increase)/g(initial biomass)) at 1.5vvm. The observed reductions in organic content by 80% (as soluble chemical oxygen demand) suggest the potential of recycling treated effluent as process water for in-plant use or for land applications. The fungal biomass contained ~50% crude protein and the essential amino acids contents were comparable to commercial protein sources for aquatic feeds (fishmeal and soybean meal), with the exception of methionine and phenylalanine.

Analysis of gas-liquid mass transfer in an airlift contactor with perforated plates

Enhanced recovery of total phenolics (TP) from defatted rice bran (DRB) subjected to prior microwave pretreatment was achieved by subcritical water extraction (SWE). The effects of microwave pretreatment temperature (60-100°C) and duration (0-30 min) were determined at raw material:water ratios (1:2 and 1:5) for SWE under fixed conditions. Optimal extraction was observed at 80°C (for 10 min, at a ratio of 1:2). With pretreatment carried out under these conditions, a shorter extraction time of 10 min was required for SWE at 200°C. Combining both optimized conditions, a TP yield of 190.4±3.3 mg/g of DRB was achieved, some 55% more than was found to be extractable from un-pretreated samples. The antioxidant activity of the extract was also greater, as indicated by a corresponding decrease in IC(50) from 38.8±0.4 to 27.7±0.5 μg/ml.