Showing papers in "Asia-Pacific Journal of Chemical Engineering in 2016"

Aggregation effects on water base Al2O3—nanofluid over permeable wedge in mixed convection

Abstract: Two-dimensional heat transfer flow of a nanofluid in the neighborhood of a stagnation point flow in the presence of mixed convection is investigated. The mathematical model consists of continuity and the momentum equations, while a new model is proposed to see the effects aggregations on water base Al2O3 nanofluid over permeable wedge. The variable wall temperature is taken into account. The Mathematica package based on homotopy analysis method is used to solve this problem. Several aspects of the aggregation parameters on velocity and temperature profiles of nanofluid are investigated and shown graphically with respect to the physical parameters involved in it. The tabular results are demonstrated for heat transfer rate and skin friction coefficient. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Perovskite materials in energy storage and conversion

Abstract: In this review, the recent progress in the application of an important category of materials, i.e. ABO3 perovskite-type compounds in the fields of energy storage and conversion, is reviewed. Four main areas, as materials for oxygen transporting membrane toward the application in oxy-fuel combustion, as key material for solid oxide fuel cells for efficient power generation from fuels, as room-temperature electrocatalysts for oxygen reduction reaction and oxygen evolution reaction, and as material for solar cells for solar energy harvest, are referred. Our past efforts in these research areas are emphasized. Some prospects about the future development in the application of perovskite materials in energy storage and conversion is proposed. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Challenges in the development of reversible solid oxide cell technologies: a mini review

Abstract: High-temperature solid oxide cells (SOCs) are attractive for storage and conversion of renewable energy sources by operating reversibly in solid oxide fuel cell and solid oxide electrolysis cell modes. Solid oxide fuel cell is the most efficient energy conversion device for the electricity generation by electrochemically direct conversion of chemical energy of fuels such as hydrogen, methanol and methane, while under solid oxide electrolysis cell operation mode, hydrogen or syngas can be produced as fuels or feedstock for liquid fuels such as methanol, gasoline and diesel using electricity from renewable energy sources. This mini review will introduce briefly the principle, status and progress in the electrochemical energy conversion and storage process by reversible operation of high temperature SOCs. The challenges in key material and performance degradation issues associated with high-temperature fuel cell and electrolysis operation of SOCs will be concisely reviewed and discussed. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Physical properties and intermolecular interaction of eutectic solvents binary mixtures: Reline and ethaline

Abstract: Despite the potentials of deep eutectic solvent (DES) for application in variety of fields, the perfect DES with the exact desired properties is hard to come by. This is due to lack of understanding of their exact nature, which would allow for appropriate choice of the DES constituents to obtain the desired properties. One way DES properties can be fine-tuned to a specific application is via mixing with another DES. This does not only allow for the formation of task specific solvent but also presents us with the opportunity of studying intermolecular forces of attraction via a macroscopic thermodynamic property (excess molar volume). In this work, the DES mixture Reline–Ethaline was synthesized at different molar fractions of Ethaline. The excess molar volume of this system was evaluated, and its effect on the physical properties of DES mixture was discussed. The physical properties measured were molar volume, viscosity, conductivity, refractive index and pH at different molar fractions of Ethaline (0.1, 0.3, 0.5, 0.7, and 0.9), and temperatures (20–80 °C). © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Synthesis and characterization of poly (ether‐block‐amide) mixed matrix membranes incorporated by nanoporous ZSM‐5 particles for CO2/CH4 separation

Abstract: In this work, poly (ether-block-amide) (Pebax MH 1657) mixed matrix membranes (MMMs) were prepared using nanoporous ZSM-5 as a filler. The fabricated membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) analysis, thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). Effects of zeoilte loading (5, 10 and 15 wt. %), and feed pressure (1, 3 and 5 bar) on CO2/CH4 separation of MMMs were investigated using constant volume/variable pressure system. SEM analysis represents a proper morphology along with proper dispersion of ZSM-5 particles within the polymer matrix. TGA analysis demonstrated that the thermal degradation temperature (Td) of MMMs increased by increasing the ZSM-5 loading. The obtained experimental results showed that both permeability and CO2/CH4 selectivity enhanced by addition of zeolite compared to neat Pebax. At low concentration of zeolite (5 wt. %), the CO2 permeability increased significantly from 122.4 Barrer to 217.9 Barrer at pressure of 1 bar. MMM that incorporated by 15 wt. % of zeolite showed the best CO2/CH4 selectivity of 33.9 at pressure of 1 bar. The CO2 permeability of MMM with 5 wt. % ZSM-5 enhanced from 217.9 to 292.4 Barrer with increase in feed pressure from 1 to 5 bar. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Study of gas–liquid mixing in stirred vessel using electrical resistance tomography

Abstract: This study presents a full operation and optimisation of a mixing unit; an innovative approach is developed to address the behaviour of gas-liquid mixing by using Electrical Resistance Tomography (ERT). The validity of the method is investigated by developing the tomographic images using different numbers of baffles in a mixing unit. This technique provided clear visual evidence of better mixing that took place inside the gasliquid system and the effect of a different number of baffles on mixing characteristics. For optimum gas flow rate (m3/s) and power input (kW), the oxygen absorption rate in water was measured. Dynamic gassingout method was applied for five different gas flow rates and four different power inputs to find out mass transfer coefficient (KLa). The rest of the experiments with one up to four baffles were carried out at these optimum values of power input (2.0 kW) and gas flow rate (8.5×10-4 m3/s). The experimental results and tomography visualisations showed that the gasliquid mixing with standard baffling provided near the optimal process performance and good mechanical stability, as higher mass transfer rates were obtained using a greater number of baffles. The addition of single baffle had a striking effect on mixing efficiency and additions of further baffles significantly decrease mixing time. The energy required for complete mixing was remarkably reduced in the case of four baffles as compared to without any baffle. The process economics study showed that the increased cost of baffles installation accounts for less cost of energy input for agitation. The process economics have also revealed that the optimum numbers of baffles are four in the present mixing unit and the use of an optimum number of baffles reduced the energy input cost by 54%.

Spatio‐temporal adaptive soft sensor for nonlinear time‐varying and variable drifting processes based on moving window LWPLS and time difference model

Abstract: Industrial plants often undergo different kinds of changes like variable drifts and time-variant problems, which may cause the degradation of soft sensors. In this paper, a spatio-temporal adaptive soft sensor modeling framework, which is based on the moving window and just-in-time learning (JITL) techniques, is proposed for nonlinear time-varying processes. The JITL (locally weighted partial least squares) can adapt the model by spatial weighting technique, and the moving window technique can adapt the soft sensor model to the new process state. Furthermore, time difference (TD) model is utilized to handle the process change of variable drifts. Case studies are carried out on a numerical example and two industrial processes. The results show the effectiveness and flexibility of the proposed soft sensor framework. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Recent development on perovskite-type cathode materials based on SrCoO3 − δ parent oxide for intermediate-temperature solid oxide fuel cells

Abstract: The slow oxygen reduction reaction kinetics as well as structural and chemical instability of cathode are the main barriers hindering the development of the solid oxide fuel cell operated at intermediate temperature. Therefore, immense efforts have been devoted to address these two demanding issues. Perovskite cathodes based on SrCoO3 − δ show promising electroactivity on oxygen reduction at intermediate temperature but are susceptible to contaminates in air. In this short review, we mainly cover the recent advances in SrCoO3 − δ-based perovskite cathode development, with emphasis on doping strategies in electroactivity enhancement and cathode tolerance to CO2. Some future research directions are also recommended at the end of this review. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Reactive absorption of NO and SO2 into aqueous NaClO in a counter-current spray column

Abstract: The experiments were performed in a spray column to study the simultaneous absorption of NO and SO2 using NaClO solution from simulated gas stream under various experimental conditions. The effects of various influencing parameters, such as absorbent concentration, reaction temperature, initial SO2 and NO concentration, and initial pH of NaClO solution on simultaneous removal of SO2 and NO, were emphatically investigated in regard to coal-fired thermal power plant stack gas emission control. The maximum removal efficiencies of SO2 and NO were found as 97% and 87.8%, respectively, at 313 K, initial NaClO solution pH 5.4 and 0.024 M NaClO concentration. The addition of CO2 in simulated gas stream was also carried out to see its influence on removal efficiency of SO2 and NO. The results using a spray column showed that NaClO can be used effectively for simultaneous removal of NO and SO2from coal-fired thermal power plant simulated gas stream. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

New application of henna extract as an asphaltene inhibitor: an experimental study

Abstract: Taking preventive measures of asphaltene precipitation is of great significance in petroleum production and development. Therefore, a new chemical remediation was developed in the current study. The major objective of this experimental study is investigation of the effects of chemically extracted henna on the behaviour of asphaltene in the Bangestan crude oil during pressure decline due to asphaltene precipitation in the coreflood experiments. The application of henna leaf-derived inhibitor and their influences on the asphaltene precipitation in the oil wells have not yet been addressed in the literature. Coreflood test results illustrate that subjection of the crude oil to chemically extracted henna decreases the asphaltene precipitation which was obtained by IP143 method. Also, it was concluded that permeability reduction with Bangestan crude oil during coreflooding with henna extract in n-hexane is less than when it was flooded with pure n-hexane. The consequence of this investigation is the first break-in application of chemically extracted henna in oil industry. To this end, the results of the present work can assist us in the subsequent researches about the usage of chemically derived natural compounds for the aims of asphaltene precipitation prevention in underground hydrocarbon reservoirs. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Modeling efforts in the key areas of thermal management and safety of lithium ion battery cells: a mini review

Abstract: Lithium ion batteries (LIBs) are no doubt a primary power source for numerous applications around us. Therefore, it is intrinsic to be long lasting and safe during operation—two issues that are tackled by thermal management. The purpose of this article is to enable the reader to get an informative overview about thermal management and safety of LIB in a quick but efficient manner. In this regard, the article reviews the modeling efforts conducted in four key areas of the topics, namely, (1) electrochemical models, (2) electrochemical–thermal coupled models, (3) cooling of LIB, and (4) LIB abuse and thermal runaway. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Nitrogen and phosphorous-doped porous carbon xerogels as metal-free catalysts for environmental catalytic peroxide oxidation of 4-nitrophenol

Abstract: This work reports an environmental benign porous carbon catalyst for the catalytic peroxide oxidation of 4-nitrophenol (4-NP) pollutant. Nitrogen and phosphorous-doped carbon xerogels as metal-free catalysts, which are namely as CX30, CX50 and CX75 with corresponding to initial concentrations of H3PO4 acid (30, 50 and 75 v/v %) were synthesized. Nitrogen gas adsorption measurements of the prepared carbon catalysts were performed at −196 °C, while Fourier transform infrared spectroscopy (FTIR) and high resolution scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) analyses were examined for the sample of CX75 which appeared high catalytic performance. The effect of various factors such as temperature, catalyst loading, H2O2 dose and initial concentration of 4-NP on the catalytic oxidation performance of the metal-free catalysts was studied at pH = 4. Results revealed that the phosphoric acid activation of nitrogen-doped resorcinol-formaldehyde xerogel developed significant influence on the porosity and surface chemistry characteristics of the hereby catalysts. Increasing the concentration of H3PO4 enhances the microporosity at expense of mesoporosity yielding micro-mesoporous carbons with surface area as high as 442 m2/g. EDS and FTIR analyses confirmed the presence of phosphorous- and nitrogen-containing functional groups with high content of carbon and oxygen groups. During catalytic wet peroxide oxidation experiments, the CX75 catalyst exhibits complete decomposition 4-NP (100%) within 60 min. Moreover, reusability experiments with this catalyst were run through three cycles and revealed high stability where up to 52.6% conversion of 4-NP in the third recycle was occurred at 120 min. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Recent advances in low-toxic lead-free metal halide perovskite materials for solar cell application

Abstract: Organic-inorganic hybrid metal halide perovskite materials have attracted exponentially increased attention for photovoltaic applications in the past few years, while the toxic lead component remains a big concern. Herein, we present the recent progress in researching lead-free perovskite light absorbers for solar cell application, and the challenges in this field are also discussed, which may shed light on further investigation of low-toxic, lead-free and efficient perovskite solar cells for sustainable solar energy utilization.

Novel amino acid-based ionic liquid analogues: neutral hydroxylic and sulfur-containing amino acids

Abstract: Deep eutectic solvents (DESs) have shown potential promise for various industrial applications. Abundant research works were carried out on Type III DES employing choline chloride as the quaternary ammonium salt in combination with a variety of hydrogen bond donors (HBDs). Despite the fact that they are cheap, biodegradable, and have a wide application in food, polymer, and pharmaceutical industries, amino acids have not been utilized as HBD for the synthesis of DES. In this work, different ammonium-based salts are used to synthesize different amino acid-based DES systems. Four different amino acids are considered, two of which are neutral amino acids, namely L-serine and L-threonine, while the other two are based on the sulfur-containing amino acids, namely L-methionine and L-cysteine. The successful DESs were characterized in terms of their physical properties. The melting point, density, viscosity, surface tension, refractive index, conductivity, and pH were measured for the successful DES systems at different temperatures ranging from 303.15 to 353.15 K. The introduction of such novel DES opens the door for performing more work on utilizing them for various chemical, biochemical, and pharmaceutical applications. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Formation damage in chemical enhanced oil recovery processes

Abstract: Generally, we do not link enhanced oil recovery (EOR) to formation damage. However, formation damage can occur during chemical EOR processes, although it is not often discussed in literature on the topic. This unfortunate gap in EOR literature ignores the fascinating fact that sometimes the formation damages in some chemical EOR processes are the very mechanisms that enhance oil recovery. This paper summarizes all of the formation damages in chemical EOR processes. The conditions and mechanisms to occur are detailed. Benefits and consequences are discussed. Solutions to promote the benefits and negate the consequences are summarized and/or proposed. This paper suggests that relevant experiments should be conducted to assess possible formation damages in chemical EOR processes. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Optimization of anionic dye adsorption onto Melia azedarach sawdust in aqueous solutions: effect of calcium cations

Abstract: Adsorption of RR141 (an anionic dye) was carried out onto Melia Azaderach sawdust (MAS) in solutions containing low concentrations of calcium ions. The effect of dye concentration, solution pH, Ca2+ concentration, adsorbent dose, and contact time was investigated by response surface methodology. The results showed that by adding 50 mg L−1 Ca2+ ions, the decolorization rate increased by 3 fold. Cation bridging between anions of RR141 and negatively charged sites of MAS was recognized as the main mechanism for the enhanced dye removal. Higher removal efficiencies were obtained at higher calcium concentrations. Solution pH (4–10) had a negligible effect on the process in presence of bridging Ca2+ ions. Initial dye concentration and adsorbent dose were the most influential factors in the process. The equilibrium time was found to be 46 min, which was unchanged at different dye concentrations (10–100 mg L−1). The dye uptake obeyed the non-linear equations of pseudo-second order kinetic model and Freundlich/Brunauer–Emmett–Teller (BET) isotherm models. The maximum adsorption capacity of 12.92 mg g−1 was calculated from the Langmuir model. Based on the obtained results, adsorptive properties of Melia Azaderach sawdust can be greatly enhanced for uptake of anionic dyes in calcium-containing solutions like natural waters. Copyright © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Side draw optimisation of a high-purity, multi-component distillation column

Abstract: Distillation columns with side draws are widely used in the process industry to refine crude methanol into high-purity methanol. Historically, industrial methanol manufacturers have concentrated on meeting strict product specifications, while methanol yield and reboiler duty optimisation has often been neglected. In this work, a steady-state model of an industrial high-purity multi-component methanol distillation column was developed using a commercial process simulator. To achieve higher recovery at optimal reboiler duty, the side draw location and side draw mass flow rates were identified as two important factors. It was determined that a combination of lowering the side draw location while reducing the side draw mass flow rate will lead to the most optimal outcome. A design of experiment was also carried out to evaluate the stability of the column at recovery rates of 97.7% (current recovery) and 99.5% (proposed high recovery). Disturbances in the feed stream were identified as having the greatest effect, while the product purity was observed to become more sensitive towards all disturbances when operating at an enhanced recovery. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Developing a mathematical model for the oxidative dehydrogenation of propane in a fluidized bed reactor

Abstract: In this research, a mathematical model to simulate a two-phase fluidized bed reactor for oxidative dehydrogenation of propane to propylene was developed. The developed model was solved numerically using the matlab software. Moreover, effects of the reaction temperature, operating pressure, feed composition, particle's size and gas superficial velocity on the reactant conversion, product selectivity and desired product's yield were understudied. The model was validated using previously published experimental data for simulation of the case at the exit of the circulating fluidized bed reactor. The results revealed that, as the temperature raised from 783 to 823 K, the propane conversion enhanced from 4.47% to 13.01%, while the propylene selectivity lowered from 85.35% to 68.03%. In addition, it was shown that doubling of the propane concentration increased the propane conversion from 4.47% to 4.73%. On one hand, doubling of the oxygen concentration enhanced the propane conversion from 4.41% to 4.47%, while on the other, tripling of the pressure led to increasing of the propane conversion from 4.47% to 5.54%. Nonetheless, this pressure enhancement lowered the propylene selectivity from 85.35% to 77.90%. Moreover, changing of the particle's type from Geldart A to B resulted in decreasing of the propane conversion from 4.56% to 1.40% and increasing of the propylene selectivity from 84.83% to 89.69%. The model further revealed that effect of the superficial velocity was not very significant. Ultimately, to predict the maximum propylene selectivity, different kinetic expressions were understudied. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Factors influencing the measured surface reaction kinetics parameters

Abstract: Further understanding of the cathode oxygen reduction reaction mechanism is one of the most important challenges for the development of solid oxide fuel cells at low and intermediate temperature. Determining the surface reaction kinetics parameters such as the surface exchange coefficient and bulk diffusion coefficient is critical to reveal the cathode process. However, the reported results from different literatures are widely divergent and sometimes the variation can reach as high as over one order of magnitude even for the same cathode material. The various original data make it difficult to judge the reaction property and possibly weaken the reliability of the parameters. In this review paper, the recent progress of the oxygen reduction reaction kinetics parameters is comprehensively summarized for typical cathode material La1−xSrxCo1−yFeyO3−δ regarding the experimental methods and principles. Emphasis is also placed on the main influenced factors which may result in the reported variation. The main purpose of this paper is to provide a summary of recent progress and reveal the possible difference source for the surface reaction kinetics of oxygen reduction reaction. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Chitosan microspheres modified with poly(ethylenimine) enhance the adsorption of methyl orange from aqueous solutions

Abstract: Chitosan (CS) microspheres were prepared by emulsion crosslinking, and the surfaces of the spheres were modified with poly(ethylenimine) (PEI) for preparing efficient adsorbents. Consequently, a series of PEI-modified CS (CS–PEI) microspheres with different ion exchange capacities (IECs) was prepared and used for the adsorption of methyl orange (MO). The adsorption performance of CS–PEI increased significantly with the increase of the sphere IECs, and the maximum adsorption capacity of 400.00 mg/g was achieved at 303 K with CS–PEI–1275, which had the highest IEC in the experiments. The adsorption process of MO well fitted the pseudo-second-order kinetic and Langmuir isotherm models, and the process was favorable at low temperature. Thermodynamic analyses showed that the adsorption of MO by CS–PEI was a spontaneous and exothermic reaction. Furthermore, CS–PEI exhibited good reusability within seven cycles of adsorption–desorption.

Removal of nitrate from aqueous solutions in batch systems using activated perlite: an application of response surface methodology

Abstract: The aim of this research is to facilitate the adsorption of nitrate on perlite acid treated with dilute H2SO4 solutions. The activated perlite with 0.06 N sulfuric acid resulted in a higher efficiency in the removal of NO3− from aqueous solutions and was adopted for subsequent investigations. To analyze the process, a significant variable, i.e. removal efficiency (%) of nitrate and three dependent parameters as the process responses, was examined through a central composite design under the response surface methodology. The optimum conditions included pH 5, contact time of 120 min and an adsorbent amount of 0.7 g. The percentage removal of NO3− in batch administrations was 91.01. © 2016 The Authors Asia-Pacific Journal of Chemical Engineering published by Curtin University of Technology and John Wiley & Sons, Ltd.

Preparation and characterization of Ni2(mal)2(bpy) homochiral MOF membrane

Abstract: As an important subclass of metal-organic frameworks (MOFs), homochiral MOFs show special ability of asymmetric catalysis and enantioselective separation via the open chiral channels or cavities. A new homochiral MOF membrane [Ni2(mal)2(bpy)]•2H2O (Ni-MB) was synthesized by a secondary growth technique, in which high energy ball milling was employed to prepare nanosized MOF seeds, and their synthesis condition were optimized. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and thermal gravimetric analysis were used to measure physicochemical properties of the MOF crystals and membranes. In particular, the homochiral MOF membranes were characterized by nano-indentation/scratch technique with high-resolution mechanical property analysis. The SEM results indicated that the membrane was continuous and integrated without observable defects; the permeation measurements of single gas show that the permeate flux of nitrogen was independent on the transmembrane pressure, further confirming the absence of macroporous defects in the as-prepared chiral MOF membranes. It is expected that the proposed chiral MOF membrane can be potentially applied to enantioselective separation in the future. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Combustion pattern, characteristics, and kinetics of biomass and chars from segmented heating carbonization

Abstract: The combustion patterns, characteristics, and kinetics were investigated by thermogravimetric analysis for raw maize straw, cotton stalk, and chars obtained from segmented heating carbonization at 300–800 °C. With increasing carbonization temperature, combustion patterns of biomass chars transform from the sequential reaction steps corresponding to pyrolysis and heterogeneous oxidation of volatiles and char to the in situ heterogeneous oxidation of fixed carbon and volatiles, the ignition temperature of biomass chars gradually increases, the ignition index does not monotonically increase, and the burnout index and combustion characteristic index decrease to different degrees. Judging from the combustion characteristic index, chars obtained from 300 to 500 °C of carbonization show better combustibility. The kinetic parameters of raw and carbonized biomass were determined by Coats–Redfern method. Different reaction mechanisms exist in oxidation processes of different chars, which attribute to the synergistic effects of homogenous oxidation of volatiles and heterogeneous oxidation of char. The kinetic parameters obtained from the variation of species and model functions exhibit kinetic compensation effect.

Waste HDPE Bottles for Selective Oil Sorption

Abstract: Selective sorption of oil using plastic waste is presented. Plastic solid waste constitutes 15% of total municipal solid waste produced across the world and is mostly either discarded in landfills or incinerated. On the other hand, pollution caused by oil spill in aquatic locations is a serious environmental concern, and several sorbents have so far been proposed to address oil spill and plastic waste problems simultaneously by converting waste into oil sorbent. However, most of the sorbents have drawbacks of either high water uptake or low oil uptake capacity. In this study, we have synthesized oil sorbent using waste plastic bottles made up of high-density polyethylene with high selectivity and high oil uptake capacity. Mechanical properties and %crystallinity using differential scanning calorimetry were also determined to provide useful insight about the as prepared sorbent. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Bubble behaviors in a lab‐scale cyclonic‐static micro‐bubble flotation column

Abstract: Bubble behaviors in the gas–liquid and lab-scale cyclonic-static micro-bubble flotation column (FCSMC) were investigated and optimized. By particle image velocimetry and charge-coupled device camera, bubble velocity and migration under low and high gas holdup conditions were measured. The particle image velocimetry measurement under low gas holdup shows that the swirling was significantly stronger than the rising in the near-axis area, and it declined as height increased. The central region contained high gas holdup and velocity. The bubble distribution under high gas holdup revealed that, in the column flotation unit, when water circulation rate (qw) increased, gas concentration moves toward the bottom. An excessively high qw drove gas downward and even caused the gas to be pulled into the pump. When aeration rate (qg) increased, the radial distribution improved but was not significant. If qg was excessive, the gas amount increased toward the top due to reflux when the rising bubbles met the free surface. Specifically, the greater bubble concentration in central region was observed under most test conditions. Additionally, an elongated ‘air column’ existed along the central axis and became more obvious with a high qw. The cyclonic inverted cone structure resulted in the gas gathering toward the center and the air column phenomena that deteriorate bubble mineralization. A non-uniform filling method was proposed to optimize the flow field. Filling with non-uniform sieve plates was proved to be more effective on bubble distribution equalization, air column inhabitation and non-axial velocity decreasing. These results provide the basis for structure optimization and process regulation of cyclonic-static micro-bubble flotation column. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Chemoenzymatic epoxidation of Karanja oil: an alternative to chemical epoxidation?

Abstract: In light of increasing concern about diminishing fossil fuel reserve, a lot of research is being focussed on the production of chemicals using renewable feedstock. Vegetable oils provide this valuable renewable feedstock as they offer a large number of possibilities. One of the interesting possibilities offered is epoxidized vegetable oil, which can be used as a plasticizer, polyvinyl chloride stabilizer, diluent, etc. Hence, a chemoenzymatic method for epoxidation of Karanja oil was investigated. The enzyme reusability, the important criteria for commercial exploitation of the technique, was also investigated. Three commercially available immobilized lipase enzymes were screened and Novozyme 435 was found to be best for chemoenzymatic epoxidation of Karanja oil. The study revealed that epoxide conversion of 80% (equivalent to chemical methods) was obtained at room temperature in the absence of any side reactions. Maximum epoxide conversion was obtained in 8–9 h at 30 °C as compared with 6 h for conventional methods at 80 °C. The reaction could also be carried out in the absence of any solvent to an extent of 56% oxirane conversion. The catalyst was found to be strongly affected by temperature and H2O2 and denatured after repeated runs, showing a maximal reusability of four runs. The enzymatic method is beyond doubt a cleaner and greener technology compared with conventional method. The advantages of energy efficiency along with 100% selectivity make it a method for the future. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Improvement in soil grouting by biocementation through injection method

Abstract: In order to reduce the cost of microbial-induced carbonate precipitation, an in situ soil improvement technique, two cost-effective methods have been developed. At first, possible replacement of costly yeast extract medium with sodium acetate for Sporosarcina pasteurii growth was evaluated. Thereafter, a sequencing batch mode of injection has been introduced. The unconfined compressive strength of 525 kPa with uniform CaCO3 distribution was obtained even for poorly graded coarse sand using the proposed injection method. According to economic considerations, by using this injection method, a substantial cost saving (53.4%) has been achieved, inducing the feasibility of biocementation technology for practical applications. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Modeling of wax deposition for water‐in‐oil dispersed flow

Abstract: Wax deposition for waxy crude oil is a long standing issue in oil production and transportation systems. With oil produced with water, the oil–water two-phase wax deposition becomes a research hotspot. Experiments of water-in-oil emulsion wax deposition were conducted in the indoor flow loop. The deposit thickness of emulsion wax deposition shows a trend of increasing after decreasing with water cuts. As the oil or coolant temperature decreases, the gelation phenomena becomes more obvious, and the turning point of the deposit thickness curve versus water cut shifts toward the lower water cut. The influence of gelling adhesion in emulsion wax deposition was discovered. A new model was developed for predicting water-in-oil dispersed flow wax deposition based on the mechanisms of molecular diffusion and gelling adhesion. The deposit thickness values predicted by the new wax deposit model for water-in-oil emulsion laminar flows with different water cuts agree well with experimental results. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.

Preparation of a ferrocene mediated bioanode for biofuel cells by MWCNTs, polyethylenimine and glutaraldehyde: glucose oxidase immobilization and characterization

Abstract: Ferrocene groups introduced polyethylenimine was adsorbed onto multi-wall carbon nanotubes attached carbon cloth before crosslinking via glutaraldehyde to develop an enzyme electrode (anode) for biofuel cell applications. Glucose oxidase was covalently immobilized onto this electrode by leftover aldehyde groups on the surface. The apparent Michaelis constant of immobilized enzyme was measured as approximately fivefold higher than that of the free enzyme. Thermal stability of immobilized enzyme was improved as estimated. Activity half-life of the immobilized glucose oxidase was determined as approximately 8 times longer than that of the free one; 2.4 mA/cm2 electrical current was obtained by using this electrode by forming a basic biofuel half-cell. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Graphene layer encapsulated metal nanoparticles as a new type of non‐precious metal catalysts for oxygen reduction

Abstract: Cheap and efficient non-precious metal catalysts for oxygen reduction have been a focus of research in the field of low-temperature fuel cells. This review is devoted to a brief summary of the recent work on a new type of catalysts, i.e., the graphene layer encapsulated metal nanoparticles. The discussion is focused on the synthesis, structure, mechanism, performance, and further research. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.