Sittha Sukkasi

Investigation of operating parameters of water extraction processes for improving bio-oil quality

Water extraction of slow-pyrolysis bio-oil, in order to improve its quality, was investigated in terms of different schemes and operating parameters. The water extraction separated the bio-oil into two phases: an aqueous phase and an organic water-insoluble fraction (or “pyrolytic lignin”). Properties of the pyrolytic lignin extracted with different extraction schemes and conditions were characterized and compared. The results showed that the water temperature and stirring time did not significantly affect the pyrolytic lignin’s properties. The water : bio-oil ratio, however, could remarkably reduce the pyrolytic lignin’s acidity. Given the findings, an effective time- and resource-saving extraction scheme with appropriate operating conditions could be devised. The resulted pyrolytic lignin, which was essentially the “upgraded” bio-oil, had notably lower acidity, higher heating value, and more stability than the starting bio-oil, due to the removal of alcohols, ketones, carboxylic acids, sugars, ethers, as well as reactive compounds by the water extraction.

Towards stabilization of bio-oil by addition of antioxidants and solvents, and emulsification with conventional hydrocarbon fuels

Bio-oil is liquid fuel produced by fast pyrolysis, typically, of biomass. Bio-oil comprises a mixture of highly oxygenated compounds, carboxylic acids and trace water. Upgraded bio-oil can be used as a substitute for conventional fuels. However, bio-oil is inherently unstable. The various compounds in bio-oil can react through many chemical reactions, such as polymerizations, during the storage of bio-oil, resulting in adverse changes in the bio-oils properties, especially increasing viscosity over time. In the present study, three sets of methods to improve the bio-oils stability were investigated: addition of antioxidants, addition of solvents, and emulsification with conventional hydrocarbon fuels. In the first set of methods, three kinds of antioxidants (propyl gallate, tert-butyl hydroquinone, and butylatedhydroxyanisole) were added in 1000-ppm concentration to bio-oil. In the second set, 10wt% of solvents, including acetone, biodiesel, ethanol, ethyl acetate, and methanol, were added to the bio-oil. Finally, the third set involved emulsification of bio-oil with different conventional hydrocarbon fuels, including diesel, gasoline, and biodiesel, using octanol as a surfactant. All test samples were subjected to accelerated aging, involving exposure to high temperature of 80°C for 5 days. The viscosity of the samples, chosen as the main indicator of the aging, was measured daily. The results showed that under the accelerated testing conditions, pure bio-oil aged significantly, with 44.65% increase in viscosity. The bio-oil with antioxidants, on the other hand, aged more slowly, with 17-20% viscosity increase. The addition of solvents also slowed down the aging drastically, especially in the case of biodiesel, with only 4.91% viscosity increase. Emulsification with conventional hydrocarbon fuels also showed promising results, with similar trends to those of antioxidant and solvent addition. All results showed that the three sets of stabilizing methods can improve the bio-oils stability significantly, with slightly varying degree of effectiveness. Selection of an optimal method in practice depends on the particular constraints and circumstances of each operation.

Safety and durability of low-density polyethylene bags in solar water disinfection applications.

ABSTRACT Solar water disinfection (SODIS) is a simple point-of-use process that uses sunlight to disinfect water for drinking. Polyethylene terephthalate (PET) bottles are typically used as water containers for SODIS, but a new SODIS container design has recently been developed with low-density polyethylene (LDPE) bags and can overcome the drawbacks of PET bottles. Two nesting layers of LDPE bags are used in the new design: the inner layer containing the water to be disinfected and the outer one creating air insulation to minimize heat loss from the water to the surroundings. This work investigated the degradation of LDPE bags used in the new design in actual SODIS conditions over a period of 12 weeks. The degradation of the LDPE bags was investigated weekly using a scanning electron microscope, Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometer, and tensile strength tester. It was found that the LDPE bags gradually degraded under the sunlight due to photo-oxidation reactions, especially in the outer bags, which were directly exposed to the sun and surroundings, leading to the reduction of light transmittance (by 11% at 300 nm) and tensile strength (by 33%). In addition, possible leaching of organic compounds into the water contained in the inner bags was examined using gas chromatography–mass spectrometer. 2,4-Di-tert-butylphenol was found in some SODIS water samples as well as the as-received water samples, in the concentration range of 1–4 μg/L, which passes the Environmental Protection Agency Drinking Water Guidance on Disinfection By-Products.

Heat-transfer modeling as a design tool for improving solar water disinfection (SODIS) containers

A simplified heat-transfer model has been developed to effectively simulate thermal performance of water containers used in solar water disinfection (SODIS) applications. The purpose of the model is to facilitate accurate, fast, and uncomplicated prediction of thermal performance of different SODIS-container designs and configurations, enabling developers to analyze new design ideas without the needs for field experiments, which are typically cumbersome and difficult to compare. The model utilizes electromagnetic absorption coefficients and other thermal properties of container materials, and water to establish control-volume heat-transfer equations that can predict the water temperature. The model’s simulated results of basic container designs agreed reasonably well with experimental results. Preliminary enhancements to the water container design were implemented—namely painting the container’s underside black and covering the container with a clear plastic bag—with the aim to achieve higher disinfection efficacy through higher water temperatures, in accordance with the fundamentals of SODIS mechanisms. The heat-transfer model predicted that both design enhancements would significantly increase the water temperature, with the black coating being more effective. Subsequent field experiments confirmed the model’s predictions.

Enhanced Solar Water Disinfection using ZnO Supported Photocatalysts

ABSTRACT Nano-structured ZnO photocatalysts on cellulose and polyester supports were developed for enhancing solar water disinfection (SODIS). The photocatalysts were fabricated by a two-step hydrothermal method, in which ZnO nanoparticles were synthesized and deposited on a cellulose or polyester support as a seed layer, followed by the growth of one-dimensional ZnO nanorods on the seed layer in a liquid bath containing zinc nitrate and hexamethylenetetramine as sources of precursors. The morphologies and phase compositions of the synthesized ZnO nanorods from different growth conditions were investigated with field emission scanning electron microscope and X-ray diffraction (XRD), respectively. The crystallinity size of the ZnO nanorods was in the range of 17–30 nm and increased with the precursor concentration. The XRD patterns also revealed that higher growth solution concentrations led to higher intensity of XRD peaks, indicating higher crystallinity. Additionally, to test for SODIS enhancement, experiments using 200-mL transparent polyethylene bags as SODIS reactors, with ZnO photocatalysts inside, and water samples containing 106 CFU of Escherichia Coli were conducted in a laboratory UVA setup. The photocatalyst with a polyester support resulted in a 15% higher disinfection efficiency than that of the one with a cellulose support. Moreover, a field test of enhanced SODIS was conducted in actual sunlight, using specially designed SODIS reactors containing ZnO photocatalysts with a polyester support. Nearly total disinfection (97–98% efficiency) was achieved within the first 15 min of every test. The treated water was also tested for zinc contents, which could be released from the photocatalysts, by ICP-OES. The results were lower than 2 mg/L. GRAPHICAL ABSTRACT

Environment-Community-Human-Oriented (ECHO) Design: A Context-Appropriate Design-Thinking Process for the Well-Being of Individuals, Communities, and the Local Environment

This work builds upon the user-centric “design-thinking” methodology to form environment-community-human-oriented (ECHO) design, a process that strives to create solutions that not only meet the needs of the potential users but also create positive experiences and meaningfully influence their communities and the environment. As important as the users, the environment and communities are also key design considerations and target beneficiaries of the design outcomes. ECHO design was applied to solve the lack-of-safe-drinking-water problem in under-resourced communities. The resulting solution was an integration of products and services, consisting of an inexpensive, easy-to-use-and-maintain, aesthetically pleasing, and environmentally friendly water-disinfecting device; a model to fit the use of the device into the local daily routines, skills, resources, communities’ cultures, social conducts, spending habits, health understanding, and environmental settings; and a business model aiming to sustain the use of the product, health-oriented mind-set, and positive long-term impacts on the individuals, communities, and the environment.

Material Safety and Integrity of Water-Filled Low-Density Polyethylene Bags in an Accelerated Weathering Investigation for Applications in Solar Water Disinfection (SODIS)

In this work, the potential use of LDPE bags as containers in the SODIS application by simulated in an accelerated weathering tester (QUV), with respect to material safety and durability, was investigated. For the material integrity, a decrease in the elongation at break from 818% (at the beginning) to 21% (after 6 weeks of UV exposure) corresponded to the long UV exposure. A significant degree of mechanical degradation was evident during 2 to 4 weeks of UV exposure. The UV-Vis results showed that the UV transmittance of the bags, mostly in the UV-B region, decreased with longer duration of UV exposure. The FT-IR results showed a slight increase in carbonyl group, particularly observable in the bags exposed under UV for 3 weeks or longer. For the material safety, the amount of plastic additives that were leached into water was negligibily small and much lower than the limit of the safety standard. The results and analyses from this work provide insights into the feasibility of LDPE as an alternative material for SODIS containers and potentially be useful for future designs of SODIS containers to improve the disinfection and durability performances.

Stabilization of Empty Fruit Bunch (EFB) derived Bio-oil using Antioxidants

Abstract Bio-oil is a promising alternative source of energy which can be produced from empty fruit bunch (EFB). Bio-oil comprises a mixture of highly oxygenated compounds, carboxylic acids and trace water. Bio-oil can be used as a substitute for conventional fuels after it is upgraded. However, the oil can react through many chemical reactions such as polymerization and lead to an increase in viscosity of bio-oil during storage. Thus, this paper explores the stabilization of empty fruit bunch derived bio-oil. The objective of this project is to select the optimum condition, to study the accelerated aging of bio-oil and the effect of addictive in stabilizing the bio-oil. The bio-oil is produced from the catalytic pyrolysis of EFB. The optimum reaction condition applied is 5 wt% of H-Y catalyst at reaction temperature of 500 °C and nitrogen flow rate of 100 ml/min. At this optimum condition, it is able to obtain the maximum bio-oil yield. The method used in this research to improve the stability of the bio-oil is through addition of antioxidants. Four different types of antioxidants which are propyl gallate (PG), tert-Butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) and calcium chloride salts (CaCl 2 ) are added to the bio-oil separately in the amount of 1,000 ppm. All the test samples are subjected to accelerated aging involving exposure to high temperature of 80 o C for 7 d. The properties of samples which are chosen as the indicator of aging are viscosity, water content and acidity. The effectiveness of antioxidants increase in the following order: CaCl 2 , BHA, TBHQ and PG. The antioxidants used are able to improve the stability of bio-oil in terms of viscosity and water content during aging. All the antioxidants helped to reduce the acidity of bio-oil except for CaCl 2 . The results from Gas Chromatography-Mass Spectrometry (GC-MS) analysis showed that the chain reaction of polymerization stopped by phenolics and decrease in carbonyls and ethers can lead to decreased in water content during aging. In addition, molecule decomposing reactions also reduced and resulted in lower acidity.