Will Gates | Deakin University (original) (raw)

Papers by Will Gates

Bentonite is a natural clay mineral widely used in the mining and solid waste containment industr... more Bentonite is a natural clay mineral widely used in the mining and solid waste containment industry, for example, as a soil mixture for the construction of seepage barriers, or as a component of geosynthetic clay liners (GCLs), to provide low hydraulic conductivity. However, degradation of bentonites generally occurs when permeated with acid solutions, such as encountered in mining applications, which may influence physical properties, and particularly, the hydraulic performance of geosynthetic clay liners. In this paper, properties such as Atterberg limits, free swell index, and fluid loss of three bentonites were measured with different concentrations of sulphuric acid solutions. These properties were found to deteriorate even with low (0.015 M) sulphuric acid solutions; higher concentrations (up to 1 M) resulted in larger degradation. X-ray diffraction and infrared spectroscopy were used to monitor the change of bentonites after interaction with the acid solutions. Acid leachates in general result in the overall degradation of the hydraulic performance of geosynthetic clay liners and potentially, any bentonite-soil mixture.

ABSTRACT A series of gas permeability tests were performed on four partially hydrated geosyntheti... more ABSTRACT A series of gas permeability tests were performed on four partially hydrated geosynthetic clay liners (GCLs) (GCL1, GCL2, GCL3, and GCL4). All GCLs consisted of essentially dry bentonite (powder or granular) sandwiched between geotextile layers. The geotextiles were held together as a composite material by needle-punching, except GCL-4, which was stitch bonded. GCL-2 had a special characteristic, which consisted of a cover nonwoven geotextile layer impregnated with powdered bentonite. The gas permeability was found to be very sensitive to the change of moisture content and volumetric water content. The results also highlighted the effects of the GCL structures (bentonite impregnation, needle punching, and stitch bonding) and bentonite forms (granular and powdered) on the gas permeability. The needle punched GCLs tended to have lower gas permeability than the stitch bonded GCLs, and the GCLs containing granular bentonite tended to have higher gas permeability than the GCLs containing powdered bentonite. The bentonite impregnation of the nonwoven geotextile also contributed to lower gas permeability. For comparable conditions, these effects resulted in a reduction of up to three orders of magnitude of gas permittivity from one GCL to another. However, the effect of the differences between the GCLs on gas permeability, at high volumetric water content (>70%), was overridden by the presence of the overburden pressure during hydration. Furthermore, the overburden pressure also had an important role in the reduction of gas permeability, which implies that the GCL should be subjected to confinement at the time of installation or hydration in order to obtain a low gas permeability.

$Research paper thumbnail of Using x-ray powder diffraction as a cost effective tool in cement industry$

Rietveld Analysis of cement diffraction patterns have been used to determined the composition of ... more Rietveld Analysis of cement diffraction patterns have been used to determined the composition of cement since John Taylor's pioneering work in the 1990's. Since then many workers have used this techniques to analyse cement and supplementary cementitious materials and their hydration products, both for research and production control purposes. Nevertheless there are a number of factors, including the amorphous content of the cement and relative proportion of mineral polymorphs present in the initial clinker, whose impact on analysis are still not completely understood. X-ray powder diffraction beamlines from the Brazilian Synchrotron Light Laboratory (LNLS) and the Australian Synchrotron, which produce more intensity and better resolution than normal x-ray diffraction sources, were used to investigate cement diffraction patterns and the hydration products of a range of cement pastes cured for up to 28 days. This study highlights the information that can be obtained from X-ray diffraction analysis for controlling and optimizing cement production and concrete durability.

Metals

Microscopic, electrochemical and surface characterization techniques were used to investigate the... more Microscopic, electrochemical and surface characterization techniques were used to investigate the effects of iron reducing bacteria (IRB) biofilm on carbon steel corrosion for 72 and 168 h under batch conditions. The organic nutrient availability for the bacteria was varied to evaluate biofilms formed under nutritionally rich, as compared to nutritionally deficient, conditions. Focused ion beam-scanning electron microscopy (FIB-SEM) was used to investigate the effect of subsurface biofilm structures on the corrosion characteristics of carbon steel. Hydrated biofilms produced by IRB were observed under environmental scanning electron microscope (ESEM) with minimal surface preparation, and the elemental composition of the biofilms was investigated using energy dispersive spectroscopy (EDX). Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to provide information on the organic and inorganic chemical makeup of the biofilms. Electrochemical techniq...

Developments in Clay Science, 2006

Publisher Summary This chapter describes X-ray absorption spectroscopy (XAS). XAS corresponds to ... more Publisher Summary This chapter describes X-ray absorption spectroscopy (XAS). XAS corresponds to a range of X-ray spectroscopic techniques based on scattering, absorption, and emission (fluorescence, auger) of X-rays by matter. Synchrotron-based X-ray sources produce an intense X-ray emission with total fluxes and flux densities several orders of magnitude greater than conventional X-ray tubes. As a result, a nearly flat spectral distribution is produced over a large range of mineralogically important elements. This and recent advances in X-ray optics, detectors, insertion, and focusing devices as well as modeling of scattering processes made XAS a valuable tool for obtaining atomic-level information not previously attainable by conventional X-ray sources. The chapter reviews synchrotron-based studies of clays and clay minerals, focusing on the application of XAS to elucidating the structure and reactivity of 2:1 phyllosilicates, with particular emphasis on smectites.

Clays and Clay Minerals, 2008

In the paper 'Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahed... more In the paper 'Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahedral smectites' from Clays and Clay Minerals, vol.

Radiocarbon, 2002

Soil organic matter (SOM), leaf litter, and root material of an Ultisol from the tropical rainfor... more Soil organic matter (SOM), leaf litter, and root material of an Ultisol from the tropical rainforest of Kakamega, Kenya, were analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotopic values as well as total organic carbon (TOC) and total nitrogen (TN) contents in order to determine trends in SOM decomposition within a very well-developed soil under tropical conditions. In addition, we quantified mineralogy and chemistry of the inorganic soil fraction. Clay mineralogical variation with depth was small and the abundance of kaolin indicates intense weathering and pedoturbation under humid tropical conditions. The soil chemistry was dominated by silica, aluminium, and iron with calcium, potassium, and magnesium as minor constituents. The relative depletion of base cations compared with silica and aluminium is an indicator for intense weathering and leaching conditions over long periods of time. Depth profiles of δ13C and δ15N showed a distinct enrichment trend down profile with a ...

Synchrotron X-Ray Methods in Clay Science

Physics and Chemistry of Minerals, 1998

This paper reports on the new application of polarized extended X-ray absorption fine structure (... more This paper reports on the new application of polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy to fine-grained layer silicates taking the Garfield nontronite as a case study. Up to now application of P-EXAFS to structural studies of layer silicates has been restricted to single phyllosilicate crystals (Manceau et al. 1988; Manceau et al. 1990), but we show here that P-EXAFS can rigorously be applied to self-supporting clay films without loss of spatial resolution. The quantitative analysis of P-EXAFS requires however the preparation of highly oriented clay films, the orientation distribution of which can be assessed by texture goniometry. The Fe K-edge linear dichroism measurements were simulated by ab initio EXAFS modeling performed on a nontronite cluster whose structure was refined by distance-valence least-squares calculations. It is shown that ab initio modeling quantitatively accounts for the angular dependence of experimental EXAFS spectra. These calculations allowed for the identification of the fundamental character of single-and multiple-scattering paths of the photoelectron, and the structural interpretation of all spectral features observed up to 6.5 for the in-plane and outof-plane radial structure functions of nontronite. In practice, P-EXAFS measurements allow the determination of the flattening angle of Fe(O,OH) 6 octahedra, cations distribution in the octahedral sheet with an enhanced sensitivity, and differentiation between dioctahedral and trioctahedral structures.

Physics and Chemistry of Minerals, 1996

Reduction of octahedral Fe in the crystalline structure of smectites influences, possibly control... more Reduction of octahedral Fe in the crystalline structure of smectites influences, possibly controls, surface-sensitive physical and chemical properties. The purpose of this study was to investigate if reduction of structural Fe by Na-dithionite or bacteria affects the chemical environment of constituent cations in montmorillonite, employing solid state multinuclear (29Si and 27Al) magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Reduction of structural Fe resulted in a positive (down field) chemical shift of the main Si Q3 (Q3(0Al)) site which was strongly correlated with Fe(II) content and inferred that distortions in Si-OT (T=Si, Al) bond angles and Si-O bond lengths occur with increasing layer charge. The line width (W) of the 29Si Q3 signal also increased with increasing levels of reduction. No change occurred in the position of the peak maximum for the octahedral Al (27AlVI) signal; however, an increased W was observed for this peak with increasing Fe(II) content. These results are attributed to decreases in Si-O-T bond angles and Si-O bond distances, corresponding to a better fit between the tetrahedral and octahedral sheets brought about by the presence of Fe(II) in the clay structure. The increased 27AlVI signal width (W) may also be due to a lessening of the paramagnetic influence of Fe(III) nuclei and enhancement of 27AlVI signals with different quadrupole coupling constants (QCC). Multinuclear MAS NMR analyses of dithioniteand microbially-reduced montmorillonite indicate that reduction of structural Fe caused reversible changes in the smectite structure, at least as far as this method could discern.

Journal of Physics: Conference Series, 2010

ABSTRACT Mössbauer spectra of octahedral Fe3+ in NAu-1 nontronite, saturated with Na+, K+, NH4+, ... more ABSTRACT Mössbauer spectra of octahedral Fe3+ in NAu-1 nontronite, saturated with Na+, K+, NH4+, Ca2+ and La3+ have been analysed as two quadrupole doublets. The interlayer cations were found to affect the mean isomer shift, the quadrupole splitting and the spectral area. By considering the statistically significant nearest cation neighbour coordination environments, the inner doublet has been assigned to an octahedral Fe3+ surrounded by three Fe3+ in the octahedral sheet and eight Si4+ in the tetrahedral sheets. The outer doublet is due to the same octahedral coordination, but combined with [7Si4+, 1Al3+] and [6Si4+, 2Al3+].

Environmental Sciences, 2005

Journal of Environmental Quality, 1998

The ability of microorganisms to reduce structural Fe in minerals has become recognized as an imp... more The ability of microorganisms to reduce structural Fe in minerals has become recognized as an important mechanism in the oxidation of pollutants in soils and sediments. To better understand the factors controlling the concentration of Fe(II) in natural deposits, samples of clayey till from sites near Havrebjerg and Sparresholm, Denmark, were incubated for up to 160 d with a combination of Pseudomonas bacteria strains. These strains were previously shown to reduce structural Fe(III) to Fe(II) in smectites. According to Eh, pH, microbial activity, and structural Fe(II) content, the incubation could be separated into four phases of which the second phase (from 4 to 10 d after inoculation) generated the most structural Fe(II). Microbial activity increased the structural Fe(II) content from approximately 10% to 20–34% of total clay Fe, a lower level than that obtained for chemically reduced subsamples (76–79%), but more similar to values typical of unweathered tills of Denmark (about 50%...

Journal of Applied Physics, 2010

We describe the use of single-plane phase retrieval tomography using a laboratory-based x-ray sou... more We describe the use of single-plane phase retrieval tomography using a laboratory-based x-ray source, under conditions where the retrieval is not formally valid, to present images of the internal structure of an Aerosil granule and a hydrated bentonite gel. The technique provides phase images for samples that interact weakly with the x-ray beam. As the method is less affected by noise than an alternative two-plane phase retrieval method that is otherwise formally valid, object structure can be observed that would not otherwise be seen. We demonstrate our results for phase imaging in tomographic measurements.

Journal of Agricultural and Food Chemistry, 2003

Hydrolysis of an insecticide/nematicide, fenamiphos [ethyl-3-methyl-4-(methylthio)phenyl-(1-methy... more Hydrolysis of an insecticide/nematicide, fenamiphos [ethyl-3-methyl-4-(methylthio)phenyl-(1-methylethyl)phosphoramidate], immobilized through sorption by cetyltrimethylammonium-exchanged montmorillonite (CTMA-clay) by a soil bacterium, Brevibacterium sp., was examined. X-ray diffraction analysis, infrared spectra, and a negative electrophoretic mobility strongly indicated that fenamiphos was intercalated within the bacterially inaccessible interlayer spaces of CTMA-clay. The bacterium hydrolyzed, within 24 h, 82% of the fenamiphos sorbed by the CTMA-clay complex. There was a concomitant accumulation of hydrolysis product, fenamiphos phenol, in nearly stoichiometric amounts. During the same period, in abiotic (uninoculated) controls, 4.6% of the sorbed insecticide was released into the aqueous phase as compared to 6.0% of the sorbed fenamiphos in another abiotic control where activated carbon, a sink for desorbed fenamiphos, was present. Thus, within 24 h, the bacterium hydrolyzed 77% more fenamiphos sorbed by organo clay than the amounts desorbed in abiotic controls. Such rapid degradation of an intercalated pesticide by a bacterium has not been reported before. Evidence indicated that extracellular enzymes produced by the bacterium rapidly hydrolyzed the nondesorbable fenamiphos, even when the enzyme itself was sorbed. Fenamiphos strongly sorbed to an organo clay appears to be readily available for exceptionally rapid degradation by the bacterium.

Geotextiles and Geomembranes, 2010

GCLs containing powdered Na-bentonite treated with different dosages of a proprietary additive in... more GCLs containing powdered Na-bentonite treated with different dosages of a proprietary additive intended to reduce the impacts of chemical interactions were permeated with three solutions: a hyperalkaline solution (1 M NaOH and 1.3 mM CsCl) having similar pH to aluminum refining leachate, a 1.3 mM CsCl solution (no NaOH), and DI water. For a given permeant solution, the hydraulic conductivity of both GCLs was similar. Thus, the higher additive dosage had no measureable impact on hydraulic conductivity. Hydraulic conductivity of both GCLs decreased by a factor of approximately 1.5-1.8 during permeation with CsCl in response to osmotic swelling induced by the low ionic strength of the CsCl solution entering the pore space. In contrast, permeation with the NaOH-CsCl solution caused the hydraulic conductivity of both GCLs to increase modestly (<50 times the hydraulic conductivity to DI water), and then level out (or decrease slightly) as a result of reduced osmotic swelling in the interlayer combined with dissolution of the mineral. For the tests conducted with CsCl solution, nearly all of the Cs was adsorbed by the bentonite. In contrast, Cs broke through readily when the NaOH-CsCl solution was used as the permeant solution. Permeation with the NaOH-CsCl solution also increased the sodicity of the bentonite by replacing bound K, Ca, and Mg on the mineral surface.

European Journal of Soil Science, 2002

The long-term effects of intermittent flooding on soil properties were studied in field experimen... more The long-term effects of intermittent flooding on soil properties were studied in field experiments on a Vertisol cropped with rice in Senegal. The dominant clay minerals were smectite and kaolinite. When the soil was reduced after flooding, its cation exchange capacity (CEC) ...