Wood service life is significantly prolonged by the use of preservatives. Unfortunately, preservative treated wood is still susceptible to weathering degradation (UV and moisture) and subsequent leaching of preserving components. These negative impacts of weathering can be reduced by the application of a coating; however, the effectiveness of the coating depends on its characteristics, especially its compatibility with preservative treated wood. In this project, the performance characteristics of semitransparent deck stains were evaluated for untreated wood samples and for samples treated with chromated copper arsenate (CCA), alkaline copper quat (ACQ) and copper azole (CA) over three years of natural and three months of accelerated weathering conditions. The parameters measured were water permeability, colour change, general appearance, checking of wood, and the coating‟s ability to reduce preservative leaching. Coatings were characterized in terms of glass transition temperature (Tg), solid content, viscosity, density, contact angle, surface tension, and film thickness. Also penetration depth of a polyurethane (PU) coating was examined using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). iii All the stains evaluated effectively reduced cumulative leaching of preservative components by about 60% on average. An analysis of the preservative gradients and residual soluble components in the ACQ-samples after weathering indicated that preferential leaching of monoethanolamine (Mea) is most likely responsible for the reduced amounts of available copper in coated treated wood samples. Also, a two-week screening test was able to provide accurate predictions of the long-term leaching performance of different coatings. There was a significant interaction effect between coatings and preservatives: solvent-based coatings showed better water repellency for CCA and untreated wood, but there was no significant difference in water repellent effectiveness between water-based and solvent-based coatings for ACQ or CA-treated wood. Overall, preservative treatments greatly enhanced coating performance. Image analysis of the samples subjected to 3 years weathering showed that coatings reduced surface checking by 30-40%. Partial least squares regression (PLS-R) modeling was used to correlate measured coating properties with their weathering performance characteristics. The modeling results showed that coatings with low Tg and high viscosity effectively reduce the leaching of preservative components and improved water repellency and visual ratings

In kraft pulp mills, lime is used to convert sodium carbonate to sodium hydroxide (Ca(OH)2). The causticizing reaction precipitates lime mud which is washed, dewatered, and calcined in a lime kiln to generate lime for reuse. Clean, dry, and more stable lime mud helps reducing the energy usage of the kiln, improving burner flame stability, minimizing ring formation, and alleviating emissions of reduced sulphur gases from the kiln stack. The dewatering efficiency of lime mud is greatly affected by the mud and liquor properties, and the equipment design and operation. The properties of the mud vary continuously due to changes in the liquor strength, lime quality and dosage, which is known as the “liming ratio”. Many studies have been carried out to relate lime mud properties to dewatering and filtration behaviours, the mechanisms by which lime mud becomes difficult to settle and filter are not well understood. A systematic study was therefore conducted to examine the effect of the liming ratio on the settling rate and filterability of lime mud. The results show that the mud settling rate and filterability decreased with an increase in liming ratio. The effect was more noticeable as the liming ratio exceeded a critical level leading to an overliming condition. The results also show that the particle size of the resulting lime mud did not appreciably change with liming ratio. Therefore, the decrease in settling rate and filterability cannot be attributed to the smaller particle size of Ca(OH)2 compared to that of lime mud as commonly believed. Rather, it was caused by a change in zeta potential of Ca(OH)2-containing mud particles.This study also shows that the zeta potential of the mud slurry increases proportionally to the free lime content in the lime mud. This suggests that the zeta potential can be used to indicate the extent of overliming in the causticizing plant. The correlation between zeta potential and free lime content can be used to develop an on-line overliming monitoring system to help regulate theamount of lime addition to the system to achieve optimum operating conditions for the mud settling and filtering equipment.

In kraft pulp mills, lime is used to convert sodium carbonate to sodium hydroxide (Ca(OH)2). The causticizing reaction precipitates lime mud which is washed, dewatered, and calcined in a lime kiln to generate lime for reuse. Clean, dry, and more stable lime mud helps reducing the energy usage of the kiln, improving burner flame stability, minimizing ring formation, and alleviating emissions of reduced sulphur gases from the kiln stack. The dewatering efficiency of lime mud is greatly affected by the mud and liquor properties, and the equipment design and operation. The properties of the mud vary continuously due to changes in the liquor strength, lime quality and dosage, which is known as the “liming ratio”. Many studies have been carried out to relate lime mud properties to dewatering and filtration behaviours, the mechanisms by which lime mud becomes difficult to settle and filter are not well understood. A systematic study was therefore conducted to examine the effect of the liming ratio on the settling rate and filterability of lime mud. The results show that the mud settling rate and filterability decreased with an increase in liming ratio. The effect was more noticeable as the liming ratio exceeded a critical level leading to an overliming condition. The results also show that the particle size of the resulting lime mud did not appreciably change with liming ratio. Therefore, the decrease in settling rate and filterability cannot be attributed to the smaller particle size of Ca(OH)2 compared to that of lime mud as commonly believed. Rather, it was caused by a change in zeta potential of Ca(OH)2-containing mud particles.This study also shows that the zeta potential of the mud slurry increases proportionally to the free lime content in the lime mud. This suggests that the zeta potential can be used to indicate the extent of overliming in the causticizing plant. The correlation between zeta potential and free lime content can be used to develop an on-line overliming monitoring system to help regulate theamount of lime addition to the system to achieve optimum operating conditions for the mud settling and filtering equipment.

This thesis describes a way to achieve higher conversion rates of sugars from lignocellulosic biomass that can then be used for cellulosic ethanol production. Using oat hulls as the biomass, several chemical and physical pretreatment techniques were explored to overcome the recalcitrance and allow access to cellulose and hemicellulose. Experimentation with enzyme cocktails and dosing was done to obtain the highest conversions of cellulose and xylan to produce sugars. High solids-loading of the substrate, 14-16%, enabled higher conversion rates and would amount to lower cost of production in a commercial facility; however, end-product inhibition by the accumulation of inhibitors is also realized. To remove inhibition, a solid-liquid separation step was implemented which allowed enzymes to operate at a higher efficiency. The best combination of pretreatment and enzymatic hydrolysis led to a glucose of 89% and xylose yield of 84%, for trials conducted in a 20L bioreactor.

This study investigated the extraction of lipids and β-carotene from microalgae using microemulsions as an alternative to current solvents. Type I and type IV microemulsions composed of 4% lecithin, sorbitan monooleate, PEG-6-caprylic glycerides, and ethyl caprate were able extract lipids from lyophilized microalgae better than hexane and ethyl caprate. HPLC quantified the extracted β-carotene, with type IV microemulsions extracting the most β-carotene at 0.137±0.074% (w/w) of the total microalgae biomass after an hour. The growth recovery of the microalgae after extraction was observed over 2 weeks. Variability in the data prevented definite conclusions about the ability of algae to grow after extraction. The type IV extractions consistently showed some signs of survival. After two weeks, a pale-green colour was observed in the 15min and 1h extractions. This study showed that microemulsions can successfully extract lipids from microalgae; future work would apply microemulsion formulations to live algal cells for in-situ extraction.

Microwave reactors are important tools in chemical synthesis, as they can lead to unprecedented reductions in reaction times and improved reaction yields. In order to scale-up the technology for greater throughput and industrial application, reactor types are moving from batch to continuous flow reactors. This research designed, built, verified and modeled a continuous flow microwave reactor. The reactor could operate under high temperature/high pressure conditions, and was connected to in-line gas chromatography/mass spectrometry, for real time sample analysis. Specifically, a pressure device was developed to enable the reactor to run under high pressure conditions (< 1100 psi) without the use of a conventional back-pressure device. The reactor design was verified using two chemical reactions, and an in-line analytic apparatus was developed to assess the potential for reactor operation with in-line GC/MS. Additionally, a computational fluid dynamic model was developed to better understand the heat and mass transfer inside the reactor.

Microwave reactors are important tools in chemical synthesis, as they can lead to unprecedented reductions in reaction times and improved reaction yields. In order to scale-up the technology for greater throughput and industrial application, reactor types are moving from batch to continuous flow reactors. This research designed, built, verified and modeled a continuous flow microwave reactor. The reactor could operate under high temperature/high pressure conditions, and was connected to in-line gas chromatography/mass spectrometry, for real time sample analysis. Specifically, a pressure device was developed to enable the reactor to run under high pressure conditions (< 1100 psi) without the use of a conventional back-pressure device. The reactor design was verified using two chemical reactions, and an in-line analytic apparatus was developed to assess the potential for reactor operation with in-line GC/MS. Additionally, a computational fluid dynamic model was developed to better understand the heat and mass transfer inside the reactor.

This study investigated the extraction of lipids and β-carotene from microalgae using microemulsions as an alternative to current solvents. Type I and type IV microemulsions composed of 4% lecithin, sorbitan monooleate, PEG-6-caprylic glycerides, and ethyl caprate were able extract lipids from lyophilized microalgae better than hexane and ethyl caprate. HPLC quantified the extracted β-carotene, with type IV microemulsions extracting the most β-carotene at 0.137±0.074% (w/w) of the total microalgae biomass after an hour. The growth recovery of the microalgae after extraction was observed over 2 weeks. Variability in the data prevented definite conclusions about the ability of algae to grow after extraction. The type IV extractions consistently showed some signs of survival. After two weeks, a pale-green colour was observed in the 15min and 1h extractions. This study showed that microemulsions can successfully extract lipids from microalgae; future work would apply microemulsion formulations to live algal cells for in-situ extraction.

The anaerobic, cellulolytic bacterium Clostridium thermocellum formed biofilms on cellulose consisting of a single layer of cells which did not secrete an extracellular polymeric matrix. Sporulation occurred under normal growth and was believed to assist with biofilm translocation to new substrates. Although the cell-substrate distance was less than 210 nm, the biofilm layer lost up to 29% of hydrolyzed oligomeric products when reactors were loaded with extreme concentrations of cellulose (up to 200 g/litre). This effect was much less severe at lower cellulose concentrations. Of the total cellulose carbon, 4% (gC/gC) was utilized for cell mass production and up to 75% was converted into primary metabolites (ethanol, acetic acid, lactic acid, carbon dioxide). Increasing the starting cellulose concentration shifted the ethanol-to-acetic acid ratio from 0.91 g/g to 0.41 g/g. Such high substrate loadings and metabolite shifts have not been previously reported and may be of interest for consolidated bioprocessing strategies. Cellulose conversion was initially limited by microbial growth, with a biofilm development rate estimated at 0.46h-1 to 0.33h-1 and where up to 20% of the substrate was consumed. Subsequently, substrate-limited conditions determined the rate kinetics. Surface accessibility for microbial colonization was the dominant rate limiting factor, while mass imposed constraints very late towards the end-point fermentation. CO2 was found to be an excellent reporter molecule for cellulose consumption and biofilm growth. Online CO2 tracking may also be used to assess the digestibility of substrates with unknown surface properties. A mathematical model that described biofilm growth, substrate consumption and product formation was found to have an excellent fit with experimental data of CO2 production which reinforced the previous findings on the cellulolytic biofilm form and function. Together, these results demonstrate that biofilms are undeniably the key to understanding the effective microbial conversion of cellulosic substrates.

Differences in biofilm formation between Scenedesmus obliquus and Chlorella vulgaris were examined, as well as the effects of substrate properties. Species selection and species control had significant effects. In non-sterile conditions, C. vulgaris shifted from planktonic (23.7% attachment) to sessile (79.8% attachment) growth, and formed films of higher average thickness (52 ± 19 µm) than in sterile conditions (7 ± 6 µm). By contrast, S. obliquus attained similar thicknesses (54 ± 31 µm and 53 ± 38 µm) in both sterile and non-sterile conditions. The effect of substrate properties was minimal. Both species grew films of similar thickness (~ 30 µm for S. obliquus, <10 µm for C. vulgaris) on materials ranging from hydrophilic (glass) to hydrophobic (polytetrafluoroethylene). Micropatterning the surface also had little effect on film formation. The results indicate that species selection and species control are more important that substrate properties in the development of microalgal biofilms.