Chemical Engineering

This paper presents our findings on the application of X-ray microtomography to characterize the internal structure of mortars that were exposed to freezing-thawing action. A microfocus X-ray CT (micro-CT) scanner was used for the nondestructive 3D imaging of internal air voids or cracks at a spatial resolution of the order of 10 microns. Four different types of mortar specimens (i.e., non-air-entrained and air-entrained Portland cement mortar, and non-air-entrained and air-entrained fly ash mortar) were scanned after being subjected to different numbers of freeze-thaw cycles. Coupled with image analysis, the void space obtained from micro-CT was characterized in three dimensions (3D) in terms of void fraction and air void size distribution, as well as, the crack width and tortuosity of the connected crack network. Results suggest that the initial air voids follow a lognormal distribution with the highest population of modal size around 30-50 μm, irrespective of the type of mortar. As the distributed air voids of non-air entrained mortars were relatively few in numbers, the fly ash mortar in particular was the least resistant against frost damage as shown by the formation of internal cracks that meander around the weaker paste-aggregate interface. Indications also suggest that these cracks are well connected and anisotropic in 3D.

Tortuosity, as being influenced by the 3D pore micro-geometry, is an important physical quantity to understand better the effect of pore structure on transport properties of cement-based materials. This study attempts to evaluate directly this pore structure-transport parameter from the microtomographic images at spatial resolution of 0.5 µm. This resolution, is by far, to our knowledge, the highest resolution reported for 3D non-invasive imaging of hardened cement pastes. The results show the feasibility of using synchrotron microtomography coupled with 3D image analysis and random walk simulation to measure the diffusion tortuosity that has a direct bearing on transport properties. The tortuosity associated with the percolating pore space seems to reflect the pore morphology that mainly controls the transport properties in young cement pastes; thus, explaining the rough agreement of the results with the computer model or experimental evidence.

Deteriorated mortars and cement pastes (w/c = 0.50) were prepared by an accelerated leaching test using electrochemical migration technique. This technique enabled the reduction of the CaO/SiO2 molar ratio to less than 2.0. Non-destructive three-dimensional imaging of the internal microstructure of the deteriorated cement matrix in hardened cement paste and mortar was performed using synchrotron X-ray computed microtomography at SPring-8, Japan. After image analysis at a spatial resolution of 0.5 μm/voxel the microtomographic images successfully visualized increased pore spaces in the deteriorated cement matrix with the effective porosity ranging from 0.31 to 0.38. In addition the diffusion tortuosity in the pore space derived from random walk simulation was also evaluated as a pore structure-transport parameter. Indications suggest that the deterioration of the cement matrix due primarily to the dissolution of portlandite decreases the diffusion tortuosity to a single digit as the degree of pore connectivity becomes larger at the submicron scale.

The aim of this paper is to present an evaluation method to aid decision makers in the prioritization and selection of appropriate countermeasures at the planning stage of site remediation. We introduced a hierarchical network (hiernet) decision structure and applied the Analytic Network Process (ANP) supermatrix approach to measure the relative desirability of the remedial alternatives using the decision maker's value judgment as input. A simplified illustrative example is presented to elucidate the process, as it is being applied to evaluate the feasible remedial countermeasures of a contaminated site caused by uncontrolled landfill. Four decision models derived from the generalized hiernet were examined to describe the effect of hierarchic functional dependence, inner dependence and feedback cycle on the derivation of the priority weights. The ANP could provide a more flexible analytical framework to break down one's judgment through a more elaborate structure in a systematic way to understand the complexity of the decision problem. The proposed method therefore may not only aid in selecting the best alternative but also may help to facilitate communication to understand why an alternative is preferred over the other alternatives through the analysis of the derived weights and its underlying decision structure.

 The public perception of risks related to waste disposal facilities appears to reflect general societal anxieties and fears, which may not have a reasonable basis. A three-tier risk assessment study was therefore conducted to evaluate the landfill disposal of asbestos-containing waste (ACW) and geothermal residues. From the tier-1 analysis, the dominant asbestiform phase was identified as chrysotile, that is tightly bound in the matrix of calcite, while arsenic, cadmium, chromium, and lead were identified as the chemicals of potential concern associated with geothermal residues. From the tier-2 analysis, none of the possible exposure pathways associated with the landfill disposal of ACW was found to be potentially significant. On the other hand, there were potentially significant pathways associated with landfill disposal of geothermal residues because of the considerable potential pollution impact of leachate on soil and groundwater quality. From the tier-3 analysis, the health risk associated with landfill disposal of geothermal residues was found to be time-dependent, since the contributions to risk from water-dependent and water-independent pathways occur at different times, as indicated by RESRAD–Chem simulations. Component pathway analyses were performed to identify critical exposure pathways. The results from model sensitivity analysis have identified the input parameters that have the most influence on the time of peak risk, and the cancer risk associated with water-dependent and water-independent pathways.

Industrial ecology is recognized as an important framework toward a circular economy wherein industrial systems minimize their environmental burden by mimicking the material cycles and energy cascades found in biological ecosystems. Advocates of such framework in planning of eco-industrial parks suggest that both economic and environmental gains can be attained by transforming the industrial production from a linear to a closed loop system. However, it is imperative first to understand and analyze systematically the barriers in implementing the concept of industrial ecology in industrial parks even at the early planning stage. This work thus proposes a problematique approach to understand and analyse such barriers toward a successful development of eco-industrial parks. A problematique is a term coined by Warfield referring to concepts and tools for a structural model of relationships among members of a set of problems. The problematique is shown to be effective in analyzing the str...

The biodiesel surrogate fuels are realistic kinetic tools to study the combustion of actual biodiesel fuels in diesel engines. The knowledge of fuel chemistry aids in the development of combustion modeling. In order to numerically simulate the diesel combustion, it is necessary to construct a compact reaction model for describing the chemical reaction. This study developed a skeletal kinetic model of methyl decanoate (MD) and n-heptane as a biodiesel surrogate blend for the chemical combustion reactions. The skeletal kinetic model is simply composed of 45 chemical species and 74 reactions based on the full kinetic models which have been developed by Lawrance Livermore National Laboratory (LLNL) and Knowledge-basing Utilities for Complex Reaction Systems (KUCRS) under the diesel like engine conditions. The model in this study is generated by using CHEMKIN and then it is used to produce the ignition delay data and the related chemical species. The model predicted good reasonable agreement for the ignition delays and most of the reaction products at various conditions. The chemical species are well reproduced by this skeletal kinetic model while the good temperature dependency is found under constant pressure conditions 2MPa and 4MPa. The ignition delay time of present model is slightly shorter than the full kinetic model near negative temperature coefficient (NTC) regime. This skeletal model can provide the chemical kinetics to apply in the simulation codes for dieselengine combustion.

Kidney problems rank 7th among the top 10 causes of mortality among Filipinos. One of the potential future treatment options is the use of bioengineered kidney. The preparation of scaffolds is the first step in kidney bioengineering and perfusion decellularization using chemicals is considered the most preferred preparation method to date. However, the use of chemicals alone requires long treatment time hence, in this study perfusion decellularization is to be enhanced by sonication treatment at varying sonication power. Decellularization was carried out by perfusing the kidney with 1% SDS and was subjected to sonication treatment with a 2h sonication and 2h rest cycle. The cycle is repeated until the kidney is clear and transparent. Washing using 1% Triton X-100 and 1x PBS then follows to remove residual SDS. The extent of cell removal was determined by H&E staining. The results showed that decellularization with sonication using 150W, 200W and 250W required a treatment time of 24h...

Recent technological advancements respond to the call to minimize/eliminate emissions to the atmosphere. However, on the average, fuel oils which is one of the major raw materials, is found to increase in sulfur concentration due to a phenomenon called thermal maturation. As such, a deeper desulfurization process is needed to obtain low/ultra-low sulfur fuel oils. In the present study, the ultrasound assisted oxidative desulfurization (UAOD) processes using the H2O2 and HPW-AC oxidizing system applied to simulated fuel (~2800 ppm sulfur in the form of dibenzothiophene, benzothiophene, and thiophene dissolved in toluene), were optimized. After the pre-saturation of the HPW-AC with the simulated fuel, H2O2 was added just before the reaction was commenced under ultrasonic irradiation. After the application of both 2k-factorial design of experiment for screening and Face-Centered Design of Experiment for optimization, it was found that 25.52 wt% of H2O2 concentration, 983.9 mg of cataly...

Polyindene (PIn) membrane was fabricated onto a zeolite 5A substrate by using plasma-enhanced chemical vapor deposition (PECVD) at low temperature. Membrane characterization was done by taking Scanning Electron Microscopy (SEM) and FT-IR measurements and the new peak was found in the plasma-derived PIn film. Membrane performance was analyzed by checking permeability of pure gases (H2, N2, and CO2) through the membrane. PECVD-derived PIn membrane showed high gas barrier properties and selectivities of 8.2 and 4.0 for H2/CO2 and H2/N2, respectively, at room temperature

The stability and emission characteristics of diesel-ethanol-coconut methyl ester (CME) blends were studied to determine the most suitable fuel blends to be applied in diesel engines. This is done in order to assess the potential of the blends as a substitute for commercially available diesel fuel used in diesel engine. The stability results of the blends using 100% and 99.5% ethanol purity showed that the fuel blends containing ethanol up to 10% and CME of 5% and greater exhibited high mutual solubility at any temperature range and were resistant to microbial growths after 3 months storage. Engine operations at low speed especially at idle-no load and using a bigger size engine lead to a minimum ignition delay and result in lower fuel consumption rate. The emission test results with the new- blended fuels showed a reduction in CO2 and increasing percentage by volume of CO2 compared to commercially available diesel. The blends could deliver an efficient combustion and could run effi...

This paper presents a response surface methodology approach in the optimizationof the carbon dioxide temperature-programmed adsorption process using a new materialreferred as nitrogen-functionalized graphene oxide. This material was synthesized byloading nitrogen groups to graphene oxide using aqueous ammonia in supercriticalcondition. Later on, it was utilized as a sorbent for carbon dioxide adsorption. This process was optimized by implementing a response surface methodology coupled with a Box- Behnken design for the effects of three factors: adsorption temperature, carbon dioxide flow rate, and the amount of adsorbent. In analyzing the response surface, a model equation was generated based on the experimental data by regression analysis. This model equation was then utilized to predict optimum values of response. Furthermore, response optimizer was also conducted in identifying factor combination settings that jointly optimize the best response.

Research on polymer materials for additive manufacturing technology in biomedical applications is as promising as it is numerous, but biocompatibility of printable materials still remains a big challenge. Changes occurring during the 3D printing processes itself may have adverse effects on the compatibility of the completed print. This prospective will put emphasis on the different additives and processes that can have a direct impact on biocompatibility during and after 3D printing of polymer materials.

Bioengineering of kidneys is a potential treatment option in addressing common problems such as incompatibility and shortage of donor organs. The first step in the kidney bioengineering process involves perfusion decellularization wherein the use of chemicals is considered the most preferred preparation method to date. However, the use of chemicals alone requires long treatment time and excessive chemical usage hence, in this study perfusion decellularization was enhanced by sonication treatment at varying sonication power (150, 200 and 250 W ). Scaffolds produced were evaluated for cell removal and preservation of structural integrity. Results revealed that decellularization with sonication using 150 W, 200 W and 250 W required a treatment time of 24 h, 16 h, and 12 h respectively compared to the 28 h treatment time of decellularization without sonication. Cells were almost and completely removed as indicated by histological analysis. Meanwhile, preservation of renal structures suc...