Greg R. Birkett

The University of Queensland | UQ · School of Chemical Engineering

Understanding the phenomena governing silica scaling in reverse osmosis (RO) relies in part on properly measuring the forces acting on silica nanoparticles in high ionic strength environments, such as the concentration polarisation zone near membranes. Characterising these interactions is challenging, given the extremely small forces acting at nano...

This work investigates the effect of various membrane substrates and coating conditions on the formation of carbon/ceramic mixed matrix membranes for desalination application. The substrates were impregnated with phenolic resin via a vacuum-assisted method followed by carbonization under an inert gas. Substrates with pore sizes of 100 nm required a...

We report adsorption isotherms of CO2 and CH4 on the zeolitic imidazolate framework ZIF-7 that exhibit gate opening features associated with a flexible framework structure. This phenomenon has been reported by others for CO2 and light alkanes (e.g. ethane, ethylene, propane), but our study presents for first time experimental data to show that CH4...

This work investigates the preparation and performance of carbon alumina mixed matrix membranes (CA-MMM) by a novel vacuum-assist method by impregnating phenolic resin into a porous alumina substrate followed by pyrolysis. Increasing the precursor concentration from 1 to 20 wt% led to greater carbon pore filling and a reduction in water flux. Syste...

Understanding the phenomena governing silica scaling in reverse osmosis (RO) relies on properly characterising the water matrix. One of the challenges to characterising water samples is the presence of inorganic nanoparticles, which are difficult to detect and analyse. In this work we develop a straightforward approach for nanoparticle trapping, de...

This work investigates the synthesis and performance of double salts for H2/CO2 separation. A series of NaMg double salts were prepared based on xMg(NO3)2: yNa2CO3: zH2O and characterised. The best sorbents reached CO2 uptake of 17.9 wt% at 0.62 MPa and 375 °C. The NaMg double salts preferentially sorbed CO2 as determined by breakthrough tests. The...

We report helium adsorption capacities and the true specific impenetrable solid volumes of a clinoptilolite-rich Escott zeolite from Werris Creek (Australia), synthetic 3A and 4A zeolites, and carbon molecular sieve 3K-172 measured by a gravimetric method at pressures of (300–3500) kPa and temperatures in the range of (303–343) K. Our helium adsorp...

The performance of reverse osmosis (RO) desalination can be limited by membrane scaling. Of particular concern is silica scale, which once deposited on the membrane is extremely difficult to remove. In this work, the deposition of silica-rich nanoparticles was considered. A novel in situ sample preparation method was developed for a microscopy inve...

Nanoporous carbon-based supercapacitors store electricity through adsorption of ions from the electrolyte at the surface of the electrodes. Room temperature ionic liquids, which show the largest ion concentrations among organic liquid electrolytes, should in principle yield larger capacitances. Here we show by using electrochemical measurements tha...

This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a fo...

Highlights 1. Colloids size is a determining factor in deposition and aggregation. 2. Alginate contributes to an enhancement of colloids/particulates attachment. 3. Removing cations from the feedwater enhances silica deposition on the trap wafer. Abstract The performance of reverse osmosis (RO) desalination is limited by scaling of the membranes. O...

A major obstacle preventing the large scale production of polyhydroxyalkanoates (PHAs) has been the lack of a reliable, low cost, large volume feedstock. The abundance and relatively low price of methane therefore marks it as a substrate of interest. This paper presents a techno-economic assessment of the production of poly-3-hydroxybutyrate (PHB)...

In this work we have performed molecular dynamics simulations of the room temperature ionic-liquid 1-ethyl-3-methylimidazolium tetrafluoroborate on a surface with graphene structured sheets. Contact angles were calculated via polynomial-fitting of two-dimensional atomic density contours. Drop size and surface interaction were varied to assess their...

Reverse osmosis (RO) brine produced at a full-scale coal seam gas (CSG) water treatment facility was characterized with spectroscopic and other analytical techniques. A number of potential scalants including silica, calcium, magnesium, sulphates and carbonates, all of which were present in dissolved and non-dissolved forms, were characterized. The...

An unconventional nanoporous organosilica membrane has been tested in a vacuum membrane distillation (MD) process for water desalination. We propose a modified approach to understand the transport mechanism of water molecules through the nanopores of this membrane. The modified approach stems from the fact that the membrane has a hydrophilic surfac...

The line tension for a Lennard–Jones (LJ) fluid on a (9, 3) solid of varying strength was calculated using Monte Carlo simulations. A new perturbation method was used to determine the interfacial tension between liquid–vapour, solid–liquid and solid–vapour phases for this system to determine the Young's equation contact angle. Cylindrical and spher...

Electric double-layer capacitors are a family of electrochemical energy storage devices that offer a number of advantages, such as high power density and long cyclability. In recent years, research and development of electric double-layer capacitor technology has been growing rapidly, in response to the increasing demand for energy storage devices...

Engineering statistics has been historically a challenge to teach due to a focus in engineering on uncertainty observation and process optimisation rather than population analysis and active experimentation. This is particularly the case in chemical engineering statistics, with a strong process focus, continuous rather than discrete data sets, and...

Interfacial gas enrichment (IGE) covering the entire area of hydrophobic solid-water interface has recently been detected by atomic force microscopy (AFM) and hypothesized to be responsible for the unexpected stability and anomalous contact angle of gaseous nanobubbles, and the significant change from DLVO to non-DLVO forces. In this paper, we prov...

In this paper, we propose a weighted test-area method to calculate surface tension by incorporating the weighting factor from the Bennett method into the free energy perturbation scheme of the test-area method. This new method was tested by comparing against the results of the Bennett and test-area methods for simulations of square well (SW), Lenna...

The contact angles of Lennard-Jones fluid droplets on a structureless solid surface, simulated using Monte Carlo simulation, are calculated by fitting isochoric surfaces and making a number of assumptions about the droplet. The results show that there are significant uncertainties in the calculated contact angles due to the choice of these assumpti...

The influence of gas velocity (3.5, 10, and 18mm/s), salt type (NaCl, NaF, NaBr, NaI and CsCl) and salt concentration (0.001–3M) on bubble coalescence in a small bubble column were studied. The bubble coalescence was determined by the relative change in the measured light intensities passing through the salt solutions and clean deionised water. It...

This paper compares the performance of the Buckingham Exponential-6 and Lennard-Jones potential models in the description of bulk phase and adsorption properties of methane on graphitic surfaces and pores. The solid-fluid potential used in the choice of the LJ model is Steele 10-4-3 equation and for the Exp-6 model, the Crowell and Chang equation w...

Adsorption is an industrially important process that remains a vibrant and continuing area of research. The current state of the art in theoretical adsorption studies is molecular simulation with its molecular level determinism of thermodynamic behaviour. This thesis aims to investigate a range of adsorption behaviour through the use of Monte Carlo...

Grand canonical Monte Carlo simulation is used to study the adsorption of gases with strong and weak molecular interaction on graphite. We choose nitrogen adsorption at 77 K, ethylene at 104 K, methanol at 240 K and ammonia at 300 K as model examples. The adsorption mechanism of these species can be studied by analysing the radial distribution and...

In this paper, the effects of surface mediation on the adsorption isotherm and isosteric heat of adsorption on a graphite surface were investigated, as the surface mediation is known to affect the intermolecular interaction of adsorbed molecules close to the surface. Kim and Steele (Phys. Rev. B 45 (11) (1992) 6226-6233) and others have assumed tha...

The characteristics of the heat of adsorption from a slit pore model of carbon are presented. This is shown to have a few key features that are always present, regardless of the pore size distribution used, as long as there is a reasonable range of pore sizes considered. The adsorption in a slit pore model is compared against the adsorption for a d...

Grand canonical Monte Carlo simulation is used to study the adsorption of nitrogen at 77 K and ammonia at 240 K to represent weakly polar and polar molecules, respectively, on infinite and finite graphite surfaces. These graphite surfaces were modeled with different percentages of carbons removed (defects) from the top graphite layer. Increasing th...

The determination of the properties of porous solids remains an integral element to the understanding of adsorption, transport and reaction processes in new and novel materials. The advent of molecular simulation has led to an improved understanding and prediction of adsorption processes using molecular models. These molecular models have removed t...

In this paper we present a series of work covering a range of aspects relating molecular simulation to experiment. The importance of surface mediation type effects to the adsorption of simple and complex gases is demonstrated. Coupled with the adsorption of simple gases is their projection area when used for surface area determination. The pressure...

The adsorption of water on carbon black has been calculated on several model graphitized carbon blacks using Monte Carlo simulation. The surface is modeled using different interaction strengths for a Steele type potential and the placement of various functional groups on the surface. The results for the various surface configurations are compared w...

The heat capacities of argon, ammonia, and methanol on carbon black at 87.3, 240, and 300 K, respectively, have been investigated. The carbon black surface has been modeled with and without carbonyl groups. Part of this investigation is a decomposition of the heat capacity into its contributions from the different interaction potentials of an adsor...

Several procedures for calculating the heat of adsorption from Monte Carlo simulations for a heterogeneous adsorbent are presented. Simulations have been performed to generate isotherms for nitrogen at 77 K and methane at 273.15 K in graphitic slit pores of various widths. The procedures were then applied to calculate the heat of adsorption of an a...

GCMC simulations are applied to the adsorption of sub-critical methanol and ethanol on graphitized carbon black at 300 K. The carbon black was modelled both with and without carbonyl functional groups. Large differences are seen between the amounts adsorbed for different carbonyl configurations at low pressure prior to monolayer coverage. Once a mo...

Adsorption of supercritical fluids is increasingly carried out to determine the micropore size distribution. This is largely motivated by the advances in the use of supercritical adsorption in high energy applications, such as hydrogen and methane storage in porous media. Experimental data are reported as mass excess versus pressure, and when these...

GCMC simulations are applied to the adsorption of sub-critical ammonia on graphitized carbon black at 240 K. The carbon black was modelled both with and without carbonyl functional groups. Large differences are seen between the amount adsorbed for different carbonyl configurations at low pressure (P < 10kPa). Once a single layer is formed on the ca...

Grand canonical Monte Carlo simulations were applied to the adsorption of SPCE model water in finite graphitic pores with different configurations of carbonyl functional groups on only one surface and several pore sizes. It was found that almost all finite pores studied exhibit capillary condensation behaviour preceded by adsorption around the func...

NPT and NVT Monte Carlo simulations are applied to models for methane and water to predict the PVT behaviour of these fluids over a wide range of temperatures and pressures. The potential models examined in this paper have previously been presented in the literature with their specific parameters optimised to fit phase coexistence data. The exponen...

We have proposed an improved method for calculating surface tension of liquid-vapour interface based on the thermodynamic route. This method combines the central difference scheme used in the test-area method and the Bennett weighting factor. This improved method shows faster convergence than the test area method as the weighting factor reduces the...