Stabilization of bulk aggregation state in semiconducting polymer solutions

Stabilization of the aggregation state in semiconducting conjugated polymer solutions during sample preparation or flow processing, such as spin coating or ink-jet printing, is crucial to warrant controllable thin-film properties for applications with polymer-based light emitting diodes (PLED). Flow-turbidity measurements on the solutions made of a widely studied conjugated polymer revealed, for the first time, that flow could result in instant and/or persistent changes in the bulk aggregation state. Current observations, nevertheless, suggested that a combination of moderately high polymer concentration and intermediately poor solvent quality can substantially stabilize the aggregation state at the stages of sample preparation, prolonged storage, and flow processing.     

Stainless steel bipolar plate coated with carbon nanotube (CNT)/polytetrafluoroethylene (PTFE) composite film for proton exchange membrane fuel cell (PEMFC)

Composite film of carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) was successfully formed by using their dispersion fluids. This CNT/PTFE composite film was electrically conductive in the range of 10 S cm⁻¹. The proton exchange membrane fuel cell (PEMFC) was assembled with the stainless steel bipolar plate coated with the CNT/PTFE composite film. This coating decreased the contact resistance between the surface of the bipolar plate and the membrane electrode assemble (MEA). Therefore, the output power of the fuel cell increased by 1.6 times.     

Advances and Challenges on Algae Harvesting and Drying

Biodiesel production from algae offers a promising prospect for practical applications among the still developing biofuel technologies. The fact that algae are capable of producing much more yield provides an edge over other types of biofuel. Though algal biofuel research is still developing and its practical application is yet to be ascertained, promising work on laboratory- and pilot-scale algae harvesting systems has been extensively reported. Because algae harvesting and drying are vital elements in biofuel production, recent advances on various algae harvesting, dewatering, and drying technologies are reviewed and discussed. Challenges and prospects of algae harvesting and drying are also outlined.     

Waste to energy: the effects of <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. on <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis> biomass and lipid productions in palm oil mill effluent

Microalgae are recognised as promising feedstock for biofuel production. The feasibility in commercial scale microalgae cultivation could be enhanced by incorporating palm oil mill effluent (POME) as culture medium, for greater biomass growth and lipid production, together with POME bioremediation. The polluting POME is generated massively in Malaysia. POME contains high concentrations of carbon and nutrients, thus it is suitable to be applied for microalgae cultivation. The approach on waste to energy should be advanced. We studied the effects of applying Pseudomonas sp. on Chlorella sorokiniana CY-1 cultivation in POME. Pseudomonas sp. was found effective in POME decolourisation prior to C. sorokiniana CY-1 cultivation. Yet, microalgae biomass and lipid productions were higher in the non-decolourised POME. Pseudomonas sp. was as well-being co-cultivated with C. sorokiniana CY-1 in ratios of microalgae versus bacteria of 1:1; 2:1 and 1:2. Biomass of 2.04 g L^?1 and biomass productivity of 185.71 mg L^?1 d^?1 were attained in ratio of 1:1. Interestingly, the lipid content exhibited was excellent (16.04%), and about twofold higher than other ratios and the control (without bacteria). Fatty acids compositions were dominated by C16:0 (32.49%), C18:1 (24.06%) and C18:2 (20.28%), which were desirable fatty acids for biodiesel production. Effective POME bioremediation achieved with chemical oxygen demand, total nitrogen and total phosphorus removal of 53.7, 55.6 and 77.3%, respectively. Co-cultivation of microalgae and bacteria can be applied in the POME treatment plant. This allows satisfactory biomass and excellent lipid yields for biofuel production, as well as effective wastewater bioremediation.     

Calculation of energy recovery and greenhouse gas emission reduction from palm oil mill effluent treatment by an anaerobic granular-sludge process

Conventional aerobic and low-rate anaerobic processes such as pond and open-tank systems have been widely used in wastewater treatment. In order to improve treatment efficacy and to avoid greenhouse gas emissions, conventional treatment can be upgraded to a high performance anaerobic granular-sludge system. The anaerobic granular-sludge systems are designed to capture the biogas produced, rendering a potential for claims of carbon credits under the Kyoto Protocol for reducing emissions of greenhouse gases. Certified Emission Reductions (CERs) would be issued, which can be exchanged between businesses or bought and sold in international markets at the prevailing market prices. As the advanced anaerobic granular systems are capable of handling high organic loadings concomitant with high strength wastewater and short hydraulic retention time, they render more carbon credits than other conventional anaerobic systems. In addition to efficient waste degradation, the carbon credits can be used to generate revenue and to finance the project. This paper presents a scenario on emission avoidance based on a methane recovery and utilization project. An example analysis on emission reduction and an overview of the global emission market are also outlined.     

Effects of Stressed Loading on Startup and Granulation in Upflow Anaerobic Sludge Blanket Reactors

The successful operation of an upflow anaerobic sludge blanket (UASB) process depends on the formation of settleable and active granular sludge. As the anaerobic bacteria are slow-growing microorganisms, a common problem encountered in UASB operation is the long startup period and the development of biogranules. In the present study, an unconventional approach to accelerate startup and granulation processes in UASB reactors has been developed by stressing the organic loading rate (OLR) without having to reach steady-state conditions. Three UASB reactors treating a synthetic feed with chemical oxygen demand (COD) of 2,500 mg/L, at a mesophilic temprature of 35°C were studied. One reactor (R1) served as a control, while the other two (R2 and R3) were operated at different stress levels upon reaching COD removal efficiency of 75 and 85%, respectively. Experimental results indicated that under stressed loading conditions, the startup, and granule development were accelerated by 45 and 33%, respectively, along with the formation of granules of superior characteristics without deteriorating loading capacity. The operating time to reach designated OLRs was also shortened by at least 30 days in the stressed reactors. The results presented indicate that the unconventional startup approach could offer a practical solution for the inherent long start-up in UASB systems with concomitant saving in time and cost.     

A photo-oxidation generated low-k dielectric film deposited by reactive evaporation of SiO

A non-stoichiometric silicon oxide film has been deposited by evaporating SiO as a source material in Ar and O₂ mixed gas. The film is composed of SiO and SiO₂, and has a porous structure. The SiO₂ results from some part of SiO reacting with O₂ and its amount depends on the pressure in the chamber. The residual SiO in the film can be photo-oxidized into SiO₂ by ultraviolet radiation with a Hg lamp. The dielectric constant of the film after photo-oxidation is 1.89±0.04 (at frequency of 1 MHz), which shows that this porous structure film is promising for potential application as a low-k dielectric.     

Boron-doped diamond microelectrodes for use in capillary electrophoresis with electrochemical detection

The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. The microelectrodes were prepared by coating thin films of polycrystalline diamond on electrochemically sharpened platinum wires (76-, 25-, and 10-microm diameter), using microwave-assisted chemical vapor deposition (CVD). The diamond-coated wires were attached to copper wires (current collectors), and several methods were explored to insulate the cylindrical portion of the electrode: nail polish, epoxy, polyimide, and polypropylene coatings. The microelectrodes were characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for Ru(NH3)6(3+/2+) and Fe(CN)6(3-/4-) at low scan rates. The microelectrodes formed with the large diameter Pt and sealed in polypropylene pipet tips were employed for end-column detection in CE. Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM phosphate buffer, pH 6.0, run buffer, and a 30-cm-long fused-silica capillary (75-microm i.d.) with dopamine, catechol, and ascorbic acid serving as test analytes. The background current (approximately 100 pA) and noise (approximately 3 pA) were measured at different detection potentials and found to be very stable with time. Reproducible separation (elution time) and detection (peak current or area) of dopamine, catechol, and ascorbic acid were observed with response precisions of 4.1% or less. Calibration curves constructed from the peak area were linear over 4 orders of magnitude, up to a concentration between 0.1 and 1 mM. Mass limits of detection for dopamine and catechol were 1.7 and 2.6 fmol, respectively (S/N = 3). The separation efficiency was approximately 33,000, 56,000, and 98,000 plates/m for dopamine, catechol, and ascorbic acid, respectively. In addition, the separation and detection of 1- and 2-naphthol in 160 mM borate buffer, pH 9.2, was investigated. Separation of these two analytes was achieved with efficiencies of 118,000 and 126,000 plates/m, respectively.     

Performance of high-rate sludge digesters fed with sonicated sludge.

A major limitation of anaerobic sludge digestion is the long hydraulic retention time (HRT) required for satisfactory stabilization which results in large digester size. This study explored a possibility of operating digesters at shortened HRTs by sonication pretreatment of secondary sludges. Four identical digesters designated D1, D2, D3 and D4 were fed with untreated and sludge sonicated at densities of 0.18 W/ml, 0.33 W/ml and 0.52 W/ml, respectively. All digesters were operated at three HRTs of 8-day, 4-day and 2-day. Comparing with the control digester (D1), total solids removal efficiencies improved by 12-19%, 17-36% and 20-39% in digesters D2, D3 and D4, respectively. The volatile solids removal was also increased by 11-21%, 17-33% and 19-36% in the respective digesters. The improved solids degradation corresponded with increase in biogas production by 1.4-2.5, 1.9-3.0 and 1.6-3.1 times, respectively. Increase in methane composition by 2-17% was also noted in all digesters fed with sonicated sludge. An analysis indicated that sonication pretreatment could enhance degradation of carbon, nitrogen and sulfur substances in the digestion. The study suggested that sonication of sludge is a possible pretreatment to shorten the digester operating HRT with improvement in solids degradation, biogas production and methane content. It can be deduced that to maintain a consistent solids loading at a desire performance, sludge digester with smaller size can be designed.