Susan Gallardo

Optimizing and Characterizing Geopolymers from Ternary Blend of Philippine Coal Fly Ash, Coal Bottom Ash and Rice Hull Ash

Geopolymers are inorganic polymers formed from the alkaline activation of amorphous alumino-silicate materials resulting in a three-dimensional polymeric network. As a class of materials, it is seen to have the potential of replacing ordinary Portland cement (OPC), which for more than a hundred years has been the binder of choice for structural and building applications. Geopolymers have emerged as a sustainable option vis-à-vis OPC for three reasons: (1) their technical properties are comparable if not better; (2) they can be produced from industrial wastes; and (3) within reasonable constraints, their production requires less energy and emits significantly less CO2. In the Philippines, the use of coal ash, as the alumina- and silica- rich geopolymer precursor, is being considered as one of the options for sustainable management of coal ash generation from coal-fired power plants. However, most geopolymer mixes (and the prevalent blended OPC) use only coal fly ash. The coal bottom ash, having very few applications, remains relegated to dumpsites. Rice hull ash, from biomass-fired plants, is another silica-rich geopolymer precursor material from another significantly produced waste in the country with only minimal utilization. In this study, geopolymer samples were formed from the mixture of coal ash, using both coal fly ash (CFA) and coal bottom ash (CBA), and rice hull ash (RHA). The raw materials used for the geopolymerization process were characterized using X-ray fluorescence spectroscopy (XRF) for elemental and X-ray diffraction (XRD) for mineralogical composition. The raw materials’ thermal stability and loss on ignition (LOI) were determined using thermogravimetric analysis (TGA) and reactivity via dissolution tests and inductively-coupled plasma mass spectrometry (ICP) analysis. The mechanical, thermal and microstructural properties of the geopolymers formed were analyzed using compression tests, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Using a Scheffé-based mixture design, targeting applications with low thermal conductivity, light weight and moderate strength and allowing for a maximum of five percent by mass of rice hull ash in consideration of the waste utilization of all three components, it has been determined that an 85-10-5 by weight ratio of CFA-CBA-RHA activated with 80-20 by mass ratio of 12 M NaOH and sodium silicate (55% H2O, modulus = 3) produced geopolymers with a compressive strength of 18.5 MPa, a volumetric weight of 1660 kg/m3 and a thermal conductivity of 0.457 W/m-°C at 28-day curing when pre-cured at 80 °C for 24 h. For this study, the estimates of embodied energy and CO2 were all below 1.7 MJ/kg and 0.12 kg CO2/kg, respectively.

Development of base metal oxide catalyst for automotive emission control

Activity of alumina was tested for CO and hydrocarbon oxidation using the flow reactor system. The mechanism of the CO oxidation was elucidated by isotopic tracer technique using a closed circulation system. CO oxidation was found to proceed via the formation of a carbonate type of intermediate species. Water enhances the CO oxidation and CO2 retards alumina activity. Carbon deposition was also investigated during CO oxidation on alumina. Carbon formed was found to act as an in-situ active site that promoted CO oxidation. Results obtained showed alumina to be promising for CO oxidation. Pb showed opposite effects on CO and hydrocarbon reactions. Hydrocarbon reactivity test conducted showed that methanol is the most reactive on alumina giving 100% conversion at 500 °C. However, carbon deposited affected the formation of several products at this temperature. Further study on methanol oxidation using alkaline treated alumina showed better performance for auto emission control. CeO2, known to have an oxygen storage capacity, was tested as an additive to alumina for methanol oxidation and propylene oxidation. Results proved that CeO2-AL2O3 gave much higher activity for CO oxidation, methanol oxidation, and propylene oxidation than alumina.

Biodegradability and toxicity assessment of trans-chlordane photochemical treatment.

The removal of trans-chlordane (C(10)H(6)Cl(8)) from aqueous solutions was studied using UV, UV/H(2)O(2), UV/H(2)O(2)/Fe(2+), UV/TiO(2), or UV/TiO(2)/H(2)O(2) treatment using either UV/Vis blue lamps or UVC lamps (254 nm). H(2)O(2), FeSO(4) and TiO(2) were added at 1700, 456, and 2500 mgL(-1), respectively. trans-Chlordane was not significantly removed in non-irradiated controls and in samples irradiated with UV/Vis. It was also not removed in the absence of surfactant Triton X-114 added at 250 mgL(-1). In the presence of the surfactant, trans-chlordane concentration was reduced by 95-100% after 48 h of UVC and UVC/H(2)O(2) treatments and 70-80% after UVC/H(2)O(2)/Fe(2+), UVC/TiO(2) and UVC/H(2)O(2)/TiO(2) treatments. Based on these results, UVC, UVC/H(2)O(2) and UVC/TiO(2) treatments were further investigated. UVC treatment supported the highest pollutant removal (100% in 48 h), dechlorination efficiency (81% in 48 h), and detoxification to Lepidium sativum seed germination and activated sludge respiration although irradiated samples remained toxic to Chlorella vulgaris. Biodegradation of the UVC irradiated samples removed the source of algae toxicity but this could not be clearly attributed to the removal of trans-chlordane photoproducts because the surfactant interfered with the chemical and biological assays. Evidence was found that trans-chlordane was photodegraded through photolysis causing its successive dechlorination. trans-Chlordane removal was well described by a first order kinetic model at a rate of 0.21±0.01h(-1) at the 95% confidence interval.

Sustainability of Water Resources for the Poor

The availability of clean drinking water is a significant concern in many rural communities around the world. The contamination of resources directly affects locals by causing adverse health effects like diarrhea and other gastrointestinal diseases. Potential solutions such as sand filtration, chlorination, and solar disinfection are effective water purification technologies. Another method includes reverse osmosis, which is the main method for water filtration in the Philippines. However, mostly due to energy and cost concerns, these technologies are not feasible applications for poor communities. To address this need for sustainable water resources, our team proposed a personal growth and service-learning program in the Philippine town of Nagcarlan. Our goals were to employ the knowledge of engineering students to use their technical skills in order to serve society. Students involved in this program have developed a personal water filter to remove contaminants, such as heavy metals, using activated carbon derived from natural resources that are biodegradable and the product of recycling waste products. Sustainability of water resources is further achieved through a community outreach program with the poor communities. Successful personal water purification at one location has the potential to motivate the replication of the proposed solution to other impoverished towns within the

Air pollution studies in Metromanila and catalysis technology towards clean air Philippines

Considerableair quality and emission data gathered in Metropolitan Manila (MM) led to the development of automobile exhaust treatment catalysts as well as their continued improvement. Findings of a 5-year (1993-1998) collaborative work on the development of base metal oxide catalysts for automobile exhaust are summarized here.

In-Situ Active Site Formation in Co Oxidation On Alumina

For the development of automotive catalysts which may fit the condition of developing countries, catalytic activity of alumina for CO oxidation was studied. It was proposed that the carbon formed in-situ acted as an active site for CO oxidation. the carbon active site was also checked by methanol oxidation on alumina which showed temperature hysteresis during consecutive heating and cooling operations. Alkali-treated Alumina did not show any indication of the temperature hysteresis. The optimal temperature for maximum carbon depostion was confirmed by thermogravimetric analysis to be 450–500 C, which well explains the hysteresis. CeO2−Al2O3 showed remarkably higher activities for complete oxidation. It seems that alumina has reasonably satisfactory activity in total clean-up of exhaust gas.

Leaching of chromium from coal ash using citric acid, oxalic acid and gluconic acid by batch leaching procedure

This study aims to leach chromium from coal fly ash using citric acid, oxalic acid and gluconic acid. Fly ash obtained from coal ash pond comprises of 28 ppm chromium. After the batch leaching procedure, the results show that 27.66% of chromium was leached using 0.3 M citric acid with the contact time of 8 hours. Also, the order of the ability of the organic acid to leached chromium are as follows citric acid > gluconic acid > oxalic acid. Moreover, mixture of 3 organic acids were used with 0.0317 M citric acid, 0.0266 M oxalic acid and 0.06265 M gluconic acid with varying contact time. Only 8.62% of chromium was leached after 24 hours using mixed organic acid.

Catalytic Dry Reforming of Methane Using Ni/MgO-ZrO2 Catalyst

Publisher Summary This study focuses on the use of 15% Ni/MgO-ZrO2 as a catalyst for CH4 dry reforming where the high basicity of MgO and the mobile oxygen species provided by ZrO2 are expected to provide high catalyst activity and stability. Methane dry reforming is one of the important routes in natural gas processing. Here, CH4 and CO2 are converted into syngas CO and H2 which later can be used as feedstock for the processing of other chemicals such as CH3OH and NH3. Methane dry reforming requires the use of catalysts, often nickel-based, to increase the reaction rate. To date, the dry reforming of methane has limited commercial application due to the rapid deactivation of the catalysts. The reactants contain carbon species that has a high potential of blocking active sites on the catalyst surface, deactivating them.