Previous studies indicated that emulsions with nano-sized droplets or nano-emulsions possess anti-microbial activity. The microstructure of water-in-oil-in-water (W1/O/W2) emulsions present interest for microbial encapsulation in food, cosmetic and pharmaceutical applications. Therefore microbe-emulsion interactions need to be characterised in order to fully explore the potential of such applications. This thesis investigated the effect of nano-emulsions on bacteria as well as W1/O/W2 emulsion feasibility for encapsulation and triggered release (altering osmotic pressure) of bacteria and in real life application by incorporating in set-style yogurt model system for protection of probiotics were investigated. Exposure of bacterial cells to nano-emulsions was found to have no significant effect on the survival or growth bacteria and cell membrane integrity was not compromised. Bacteria had no effect on the stability of nano- and double emulsions. The release of bacteria form W1/O/W2 emulsion occurred due to the bursting of the oil globules independent of diffusion mechanisms and be controlled by altering the structure of W1/O/W2 emulsion. W1/O/W2 emulsion had a significant effect on texture and physicochemical properties of yogurt but no effect on bacterial growth kinetics while probiotics maintained high viability at the end of the fermentation. In summary, this thesis demonstrates the feasibility and applicability of W1/O/W2 emulsion for the encapsulation of microbial cells for the purpose of their protection and triggered release. The results of this thesis can be used in the formulation of better probiotic products, segregation, protection, and release of microbial cells during fermentation as well as for in vivo delivery of fermentation.

This research is concerned with the bioleaching of chalcopyrite (CuFeS\(_2\)) by Thiobacillus ferrooxidans (ATCC 19859), which has been carried out in shake flasks (250 ml) and a 4-litre stirred tank bioreactor. The effects of experimental factors such as initial pH, particle size, pulp density and shake flask speed have been studied in shake flasks by employing cell suspensions in the chalcopyrite concentrate with the ATCC 64 medium in the absence of added ferrous ions. The characterisation of T. ferrooxidans on chalcopyrite concentrate was examined by investigating the adsorption isotherm and electrophoretic mobility. Subsequently, a mechanism for copper dissolution was proposed by employing relevant experiments, including the chemical leaching of chalcopyrite by sulphuric acid and ferric sulphate solutions, bioleaching of chalcopyrite in the presence of added ferric ions, and cell attachment analysis by scanning electron microscopy. Following the above, the work then focused on the bioleaching of the chalcopyrite concentrate in a stirred tank bioreactor for the purpose of scaling up, and investigated the effects of agitation speeds. Finally, the bioleaching of low-grade copper ores has been briefly studied. The results show that the rate of copper dissolution has a positive relationship with bacterial growth, particularly with respect to bacterial attachment, which has an important role based on adsorption isotherm and scanning electron microscopy studies. However, it is not only bacteria that play an important role in copper dissolution; also the strength of sulphuric acid can influence copper solubility. For example, copper dissolution can be achieved using a sulphuric acid solution of pH 1.5, giving a concentration of about 1 g/l copper after 25 days. The results obtained from the adsorption isotherm of T. ferrooxidans and the electrophoretic mobility of chalcopyrite particles before and after interaction with each other has proved the fact that the changes in surface chemistry occurred when bacterial interactions on the mineral surface took place. Furthermore, agitation speed have a significant influence on cell growth, metal dissolution and cell adsorption ratio when carried out in shake flasks and a stirred tank bioreactor. The bioleaching results for different shake flask speeds (i.e. 100, 200 and 300 rpm) in shake flasks displayed that shake flask speed above 100 rpm was detrimental to bacterial growth and thus copper dissolution. For the bioreactor experiments, agitation was performed within a rotor speed range of 50, 100, 150 and 200 rpm. A rotor speed of 150 rpm represents the most suitable conditions for bacterial growth and the percent extraction of copper dissolution amongst those considered. In conclusion, the concentration of copper dissolution for all pulp densities reached its maximum at a concentration of 4.8 ± 0.2 g/l after 30 days leaching time. This indicted that copper dissolution has a limited solubility; this may be because the chalcopyrite particle surface was covered by mineral and bacterial deposits over the period of bioleaching time as described in the SEM analysis of the bioleaching surface. Finally, this work attempted to extract copper from a low-grade ore using bioleaching techniques. However, initial bioleaching tests proved that T. ferrooxidans could not leach copper and iron from the low-grade copper ores due to the chemical composition of the gangue minerals (mainly carbonates). This is due to the neutralising action of carbonates, which create an environment in which the pH is too high for the acidophilic bacteria to grow.

In this thesis, a systematic investigation has been carried out to study the effect of cations and anions on the interactions and aggregation of silica nanoparticles in ionic liquid colloidal suspensions. Suspensions of hydrophobic and hydrophilic silica nanoparticles in four ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate, [C\(_2\)mim][BF\(_4\)], 1-butyl-3-methylimidazolium tetrafluoroborate, [C\(_4\)mim][BF\(_4\)], 1-ethyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide, [C\(_2\)mim][NTf\(_2\)], and 1-butyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide, [C\(_4\)mim][NTf\(_2\)], have been studied. Shear thinning rheology was observed in all systems. Suspensions of [C\(_2\)mim][BF\(_4\)] and [C\(_4\)mim][BF\(_4\)] showed shear thickening behaviour at high hydrophilic silica nanoparticle concentrations. Magnetic resonance velocity imaging experiments were performed to study the local rheology of the suspensions, which compared well with the bulk rheology, but indicated shear banding in suspensions of [C\(_4\)mim][NTf\(_2\)] with hydrophilic nanoparticles. No hydrogen bonding, between either cation or anion with silica nanoparticles, was observed by IR spectroscopy. With increasing silica concentration, a decrease in the NMR \(T\)\(1\) relaxation time of protons on the imidazolium ring, of the cation, was observed for all ionic liquids indicating it is the cation that interacts with the nanoparticles. For all ionic liquid suspensions investigated, clusters of nanoparticles were observed by dynamic light scattering. However, for suspensions of hydrophilic silica in [C\(_4\)mim][NTf\(_2\)] and hydrophobic silica in [C4mim][BF4], high proportions of single nanoparticles were also present. These data have been interpreted in terms of the formation of colloidal gels and glasses.

5-Hydroxymethylfurfural (5HMF) can be produced from lignocellulosic biomass which is a non-toxic and biodegradable source. However, 5HMF is a useful feedstock for the production of Dimethylfuran (DMF), which a biofuel with characteristics similar to gasoline. In this study, a novel self-catalysed Deep Eutectic Solvent (DES) was formulated, which are ChCl-to-p-TSA (DES1), DEAC-to-p-TSA (DES2) and ChCl-to-adipic acid (DES3). The acid components perform a dual role as a hydrogen bond donor (HBD) and as a catalyst for the dehydration of fructose to 5HMF. The study was carried in a batch system at temperature (50–110 °C), reaction time (5–180 min), fructose-to- DES mass ratio (2.5–100 g/g) and DES mixing salt-to-acid ratio 0.5:1–2:1. The reaction kinetics and the effect of the novel DES composition on the dehydration reaction were also studied. It was found that fructose was readily dehydrated to 5HMF with yield of 78.3% at a temperature of 80 °C, reaction time of 60 min, DES molar mixing ratio of 1.5:1, and a feed ratio of 5. DES2 achieved a 5HMF yield of 84.8% at the same condition as DES1 except at a different molar mixing ratio of 0.5:1 (DEAC-to-p-TSA). Conversely, DES3 accomplished 100% fructose conversion and 5HMF yield and selectivity of 90.8% at a reaction temperature of 90 °C and at a reaction time of 120 min, using a DES molar mixing ratio of 1:1 and feed ratio (initial fructose) of 2.5. The reaction kinetics studied showed that DES1 and DES2 are approximately first order while DES3 1.8.

Spent cider lees(yeast), a by-product of the cider industry, was subjected to subcritical water in a batch process over a temperature range of 100 °C to 300 °C. The efficacy of subcritical water to convert the waste biomass into a mixture of valuable compounds was investigated by studying formed products in the extracts. At milder temperatures (up to 150°C), yeast intracellular contents such as proteins were released. Also, phenolic compounds which were previously adsorbed on cell walls during fermentation start to release, which was shown for the first time, leading to an increase in the antioxidant activity of the extracts (maximum 80g ascorbic acid equivalent in 100 ml). The release of phenolics was compared to organic solvent extraction and the same level of extraction was observed in subcritical water treatment. At higher temperatures, polymers of the yeast cell wall started to solubilise producing monosaccharides which later were converted to hydroxymethyl furfural (HMF). Kinetics of HMF synthesis were determined using first order kinetics suggesting that milder conditions are required for HMF production when compared to the same process using cellulose as substrate. Results support the potentials of the studied feedstock as a substrate for numerous bio-based chemicals.

This thesis describes the synthesis, properties and structural characterisation of Mg\(^2\)\(^+\), Mn\(^2\)\(^+\)and Ti\(^4\)\(^+\) pyrophosphates and Li and V substituted analogues. α and β polymorphs of MgH\(_2\)P\(_2\)O\(_7\), were isolated by a novel acid melt synthetic route. Both polymorphs crystallised in monoclinic space groups, with α-MgH\(_2\)P\(_2\)O\(_7\) isostructural with NiH\(_2\)P\(_2\)O\(_7\) and β-MgH\(_2\)P\(_2\)O\(_7\) isostructural with CaH\(_2\)P\(_2\)O\(_7\). Rietveld refinements of NPD data gave excellent fits to both structural models. MgLi\(_0\)\(_.\)\(_8\)H\(_1\)\(_.\)\(_2\)P\(_2\)O\(_7\)was also isolated with Rietveld refinement suggesting two similar possible structural models. MnH\(_2\)P\(_2\)O\(_7\), a structural polymorph of β-MgH\(_2\)P\(_2\)O\(_7\) was also synthesised via a similar route. Magnetic analysis revealed MnH\(_2\)P\(_2\)O\(_7\) to be paramagnetic, with a small antiferromagnetic component. Incorporation of Li was again achieved via the addition of lithium carbonate during synthesis. Rietveld refinement of NPD data suggests a similar structure to that of MnH\(_2\)P\(_2\)O\(_7\) and a composition of MnLi\(_0\)\(_.\)\(_5\)H\(_1\)\(_.\)\(_5\)P\(_2\)O\(_7\). A metastable polymorph of TiP2O7 has been successfully synthesised at low temperature and adopts a structure similar to the ideal cubic structure. Incorporation of vanadium resulted in an expansion of the unit cell. Both phases undergo a phase transition above 275°C to the ideal cubic structure. Addition of vanadium results in an unusual uniform spherical morphology unseen in parent phase.

IT-­PEFC operating at 120°C and not the usual 80°C has many advantages, such as faster chemical reactions. If the gas humidification is reduced, simpler and lighter humidifiers can be used, leading to a reduction in the fuel cell total cost. However, at this condition the current commercial membrane Nafion is not able to hold water and perform satisfactorily. Therefore, in this study the application of multilayer membranes for IT-PEFC was investigated. These membranes were divided into two groups, a first with external layers of Nafion and an inner layer of sulphonated polyindene, and a second with external layers of Nafion and an inner layer of graphene oxide. The membrane preparation method was also investigated. The multilayer membranes were prepared by hot pressing and solution casting. As a result, cast multilayer membranes showed better performance and proton conductivity than hot pressed. Delamination and low interface interaction were the main drawbacks for hot pressed membranes. Cast multilayer sulphonated polyindene membranes showed higher performance than Nafion at 120°C and 20% of relative humidity. In the meantime, cast graphene oxide multilayer membranes showed higher water uptake and open circuit voltage than Nafion.

This work investigates the advantages of a multi-stage supercritical water oxidation (SCWO) reactor over a single-stage configuration in treating dimethylformamide (DMF), a model compound representing nitro-organic wastewaters. Single-stage SCWO of complex wastewaters was also investigated. A PFR rig was designed and constructed to investigate reactor temperature, initial DMF concentration, stoichiometric ratio, residence time and oxidant distribution effects on component yields. Reaction temperature was the critical variable for treatability; T>500\(^0\)C caused near-complete DMF/TOC removal at relatively short residence times (approx. 6 s). DMF SCWO displayed Arrhenius-type kinetics, and the DMF (1) and O\(_2\) (0.36) reaction orders, activation energy (140 kJ mol\(^-\)\(^1\)) and pre-exponential factor (1x10\(^1\)\(^2\) M\(^0\)\(^.\)\(^3\)\(^6\) s\(^-\)\(^1\)) were evaluated. Certain injection configurations resulted in higher TOC removals than single-stage, particularly when the second injection occurred at 0.5L and delivered 50 – 67% of the oxidant, although ammonia yield exceeded those in single-stage SCWO at these points. Single-stage SCWO outperformed a small number of configurations. T>500\(^0\)C was shown to be suitable to treat complex wastes. Complete conversion of TOC to products likely occurs within 10\(^2\) s. It was seen that TOC value alone may not be a suitable input when attempting to determine treatability in SCWO and that composition must also be considered.

Heat transfer data are reported for the condensation of steam-toluene and steam-trichloroethylene eutectic mixtures on 25.4 mm diameter oxidised copper and gold plated horizontal tubes. Data are also presented for the condensation of pure steam, toluene and trichloroethylene on the oxidised copper tube and the film heat transfer coefficients obtained agree to within ± 20% of the Labunstov form of the Nusselt equation. For the binary immiscible systems the heat transfer coefficients decrease as the temperature difference increases, with the oxidised copper surface giving higher coefficients than the gold. These differences are attributed to the two observed fundamental mechanisms of condensation, a channelling mode on the oxidised copper and a standing drop mode on the gold. Models based on the different mechanisms are proposed and predict the experimental results to within ± 20%. Finally it is postulated that the temperature dependent mutual solubilities affords an explanation of the formation of the large number of very small droplets observed during the condensation of these eutectic mixtures.

Roll compaction is a dry granulation method. In the pharmaceutical industry it assists in binding tablet ingredients together to form a larger mass. This is conducted to ease subsequent processing, decrease dust, improve flowability, improve material distribution, more suitable for moisture and heat sensitive materials than wet granulation methods, minimises operating space and suited for a continuous manufacturing set-up. In pharmaceutical roll compaction various types of powder material mixtures are compacted into ribbon that are subsequently milled and tableted. The aim of this research is to investigate the use of intelligent software (FormRules and INForm software) for predicting the effects of the roll compaction process and formulation characteristics on final ribbon quality. Firstly, the tablet formulations were characterised in terms of their particle size distribution, densities, compressibility, compactibility, effective angle of friction and angle of wall friction. These tablet formulations were then roll compacted. The tablet formulation characteristics and roll compaction results formed 64 datasets, which were then used in FormRules and INForm software training. FormRules software highlighted the key input variables (i.e. tablet formulations, characteristics and roll compaction process parameters). Next these key input variables were used as input variables in the model development training of INForm. The INForm software produced models which were successful in predicting experimental results. The predicted nip angle values of the INForm models were found to be within 5%, which was more accurate to those derived from Johanson’s model prediction. The Johanson’s model was not successful in predicting nip angle above the roll speed of 1 rpm due to air entrainment. It also over-predicted the experimental nip angle of DCPA and MCC by 200%, while the approximation using Johanson’s pressure profile under-predicted the experimental nip angle of DCPA by 5-20% and MCC by 20%.