• Energy Research
• 6. Clean water close

An ancient technology of solar-driven water evaporation and distillation has recently been revived due to the concept of interfacial solar evaporation and the development of photothermal materials. There have been many research interests in improving solar light harvesting and solar-to-water evaporation efficiency within these systems, including new photothermal materials search, structural engineering, and thermal management. The application horizon of both solar-driven water evaporation and distillation has been broadly expanded beyond their conventional domain, including now wastewater treatment, seawater desalination, steam sterilization, electric generation, and chemicals/fuels productions. This dissertation focused on designing of photothermal materials and their applications to clean water production. More specifically: (1) a bi-layered porous rGO membrane with a polystyrene (PS) foam as the heat insulator was designed and proved to be effective for reducing heat conduction to the bulk water and to improve the solar-to-water evaporation efficiency, (2) a tandem-structured SiC-C ceramic monolith was prepared and demonstrated to be mechanically and chemically stable to withstand physical or chemical cleaning during long-term use in real seawater and wastewater, (3) in order to simultaneously treat the contaminated water and get clean distillate water, multi-functional SiC foam modified with mesoporous Au/TiO2 nanocomposites has been prepared, which was demonstrated to possess both photocatalytic reduction and oxidation abilities for complex wastewater treatment, and (4) when the water source was contaminated by VOCs, another efficient multi-functional photothermal material was designed with a honeycomb ceramic plate as the matrix material, and a CuFeMnO4 nanocomposite coating layer acting as both photothermal material and Fenton agent for VOCs removal. Therefore, the light absorption property of photothermal material could be improved by using a porous structure, tandem-structure, porous foam or 3D structure. The solar-to-water evaporation efficiency was improved by including a heat insulator and the reduction of the water channels’ dimension. The ceramic-based material showed potential for long-term use with high mechanical strength to endure physical cleaning. Multi-functional photothermal materials were successfully developed for complex wastewater treatment and clean water generation.

Electrocatalysis contributes to a huge extent in a large array of research fields and applications, including corrosion science, electroanalytical sensors, wastewater treatment, electro-organic synthesis and more importantly, energy conversion applications. Of the many electrocatalytic processes, the oxygen evolution reaction (OER) and triiodide reduction reaction (IRR) are of widespread importance in electrochemical cells and dye-sensitised solar cells (DSSCs). OER is a key half reaction in electrochemical water splitting, direct solar-to-electricity driven water splitting and metal-air batteries. The high cost of efficient benchmark electrocatalysts, such as RuO2 or IrO2, however, is a major drawback of OERs. While, IRR plays a significant role in DSSCs, which must be electrocatalysed at the counter electrode to complete the external circuit in real devices and thereby successfully convert solar energy to electricity. Traditionally, Pt is accepted as an ideal benchmark electrocatalyst for IRR, but its high cost and scarcity limits broad application of DSSCs. Thus, extensive effort has been made to find active alternative electrocatalysts with low-cost, high electrocatalytic activity and excellent stability for OER and IRR to the noble metals (Ru, Ir and Pt). Therefore, a rational design of earth-abundant and low-cost electrocatalysts for OER and IRR maintains a paramount significance for energy conversion applications to meet the constantly growing demand for energy supply.

Development of alternative fuel refineries, in order to improve global sustainability through increased biofuel production, has been increasingly supported by both government and private companies. Thermochemical processes such as hydrothermal liquefaction (HTL) and pyrolysis are leading technologies in this area. However, characterization, treatment, and reuse of aqueous by-products produced by such processes have received little attention. This dissertation is focused on aqueous phase characterization and catalytic advanced oxidation processing in novel microscale reactors. Novel char catalysts and improved process design were developed for efficient removal of organic contaminants. Small acids, cyclic pentenes, and carboxylic compounds such as phenol were initially identified. Model compounds were chosen based on these findings, and catalytic wet oxidation (CWO) processes in batch reactors conducted, in order to obtain reaction rate kinetics. The mechanism of compound oxidation was developed and shown through DFT analysis to be a production of hydroxyl free radicals ( ) in the presence of an oxidant and the N-doped char catalyst. The free radicals readily react with the dissolved organic compound, which was further confirmed with a FeO-N-doped char catalysts in a modified Fenton-like reaction system. In order to better develop a treatment processes which could integrate with a biorefinery, all process engineering experiments were conducted in a continuous solid-catalyzed microscale-based reactor utilizing the FeO-N-doped char catalyst. Time scale analysis was used for reactor geometry optimization in an effort to reduce diffusion time. The design led to a parallel plate reactor with channel depth of 500 microns. Thermochemical aqueous phases produced by pilot scale processes were characterized in detailed by extensive analytical methods. Traditional methods of spectroscopic analysis were limited in the ability to identify more complex oligomeric compounds and thus newer methods such as ICR-MS were utilized. The aqueous phases were successfully treated by the novel catalyst in the microreactor with removal of over 70% total organic carbon present at atmospheric pressure and at 90 °C. Some aqueous phase samples were more complex in nature however, successful decontamination was achieved. Catalytic wet oxidation processing in microscale-based reactors proves to be a plausible treatment option for process water in biorefineries.

A principal objective of this work was to study the conversion of coal to C{sub 2} {minus} C{sub 4} hydrocarbons in a two-stage reactor system. Coal was converted to liquids at 440{degrees}C in a stirred batch autoclave using tetralin as the hydrogen donor solvent. The liquids produced were separated from the unreacted coal and ash by filtration. The liquids were then fed into a second stage fixed bed reactor containing sulfided Ni-Mo/Al{sub 2}O{sub 3} and SiO{sub 2{minus}}Al{sub 2}O{sub 3} catalyst. The liquids were hydrocracked on the dual functional catalyst giving high yields of C{sub 2} {minus} C{sub 4}. hydrocarbons. The pressure was 1800 psi and the temperatures were in the range of 425 to 500{degrees}C. The kinetic parameters of the conversion of coal liquids to gases were determined. The activation energy was determined.

Currently Indonesia is still heavily dependent on fossil fuels as an energy source. To reduce dependence on oil and meet global enviromental requirements, one way is with the development of enviromentally friendly fuel that is and alternative energy derived from plant oil called biodiesel. This study uses a Completely Randomized Design (CRD) with five treatments, S1 (Reaction transesterification 1 hour), S2 (transesterification 2 hours), S3 (transesterification 3 hours), S4 (transesterification 4 hours), and S5 (transesterification 5 hours) with three replications. The data were analyzed using ANOVA, continued by DNMRT at 5 % level. The results showed that the transesterification reaction time significantly (P0.05) on influenced the acid number, total glycerol, flash point, saponfication. The analysis has been carried obtained the best treatment is S5 with the results said saponfication (103.52 mg KOH/g), the acid value (1.29 mg KOH/g), total glycerol (0.19 %), viscosity (2.21 cSt), water content (0.02 %), flash point (115°C ), and the level of methyl ester (99.32 %).

Abstract This study investigates whether the rate of cooling of pyrolysis vapors affects the composition of the resulting bio-oil. Pure cellulose was pyrolyzed in a laboratory-scale fluidized bed reactor at 500 °C and the bio-oil collected in either an indirect contact heat exchange (conventional water-cooled condenser system) or a direct contact heat exchange (liquid quench) system developed in our laboratory. The liquid quench system was estimated to achieve a seven-fold increase in cooling rate compared to the water-cooled condensers. Direct contact cooling in the quench system also eliminated temperature gradients experienced by films of bio-oil running down the walls of the water-cooled condensers. The combination of these two factors helped reduce secondary decomposition of primary pyrolysis products, especially anhydrosugars such as levoglucosan. The quench system increased the yield of levoglucosan by over 20% while minimally effecting yield of other compounds. The concept of direct contact cooling was applied to a pilot-scale, lignocellulosic biomass pyrolysis plant using water as a more practical quench media than liquid nitrogen. As with the liquid nitrogen quench, the water flashed to gas while the heavy ends of the bio-oil condensed to liquid. The quench vessel was operated above the dew point of the water to assure that it left the vessel as gas along with produced water and light ends of bio-oil, which were recovered in a condenser as an aqueous phase. In pyrolysis experiments with red oak, the quench vessel increased the yield of heavy ends by 15% compared to conventional condensers. These results encourage the design of bio-oil recovery systems that can rapidly quench products to achieve high yields and improve the quality of bio-oil.

Pacific Northwest Laboratory has completed an initial investigation of the effects of physical and chemical properties of biomass feedstocks relative to their performance in biomass energy conversion systems. Both biochemical conversion routes (anaerobic digestion and ethanol fermentation) and thermochemical routes (combustion, pyrolysis, and gasification) were included in the study. Related processes including chemical and physical pretreatment to improve digestibility, and size and density modification processes such as milling and pelletizing were also examined. This overview report provides background and discussion of feedstock and conversion relationships, along with recommendations for future research. The recommendations include (1) coordinate production and conversion research programs; (2) quantify the relationship between feedstock properties and conversion priorities; (3) develop a common framework for evaluating and characterizing biomass feedstocks; (4) include conversion effects as part of the criteria for selecting feedstock breeding programs; and (5) continue emphasis on multiple feedstock/conversion options for biomass energy systems. 9 refs., 3 figs., 2 tabs.

The Sulfur-Iodine thermochemical hydrogen production process (SI process) consists of the Bunsen reaction section, the H2SO4 decomposition section and the HI decomposition section. The HIx solution (HI-I2-H2O) could be recycled to Bunsen reaction section from the HI decomposition section in the operation of the integrated SI process. The phase separation characteristic of the Bunsen reaction using the HIx solution was similar to that of SO2-I2-H2O system. However, the amount of produced H2SO4 phase was too small. To solve this problem, the study was carried out by the pressurized continuous Bunsen reaction. Bunsen reactions were performed at variation of feed rate of SO2/O2 gas in 3 bar of atmosphere. Also, it was performed to check the effects of the residence time in the reservoir on the characteristics of Bunsen products. As the results, the concentration of H2SO4 and HI in Bunsen products was increased with increasing the amounts of SO2. When the residence time in the reservoir increased, the concentration of H2SO4 and HI in HIx phase was decreased by reverse Bunsen reaction.

Electrochemical processes enable a new generation of energy-efficient desalination technologies. While ion electrosorption via capacitive deionization is only suitable for brackish water with low molar strength, the use of Faradaic materials capable of reversible ion intercalation or conversion reactions allows energy-efficient removal of ions from seawater. However, the limited charge transfer/storage capacity of Faradaic materials indicates an upper limit for their desalination applications. Therefore, a new electrochemical concept must be explored to exceed the current state-of-the-art results and to push the desalination capacity beyond 100���200 mgNaCl/gelectrode. In this proof-of-concept work, we introduce the new concept of using metal���air battery technology for desalination. We do so by presenting performance data for zinc���air desalination (ZAD) in 600 mM NaCl. The ZAD cell provides a desalination capacity of 0.9���1.0 mgNaCl/cm2 (normalized to the membrane area; corresponding to 1300 mgNaCl/gZn) with a charge efficiency of 70% when charging/discharging the cell at 1 mA/cm2. The energy consumption of ZAD is 68���92 kJ/mol.