1,720,965 research outputs found
Potential Approach for the Adsorption of Phosphate from Agricultural Runoff using Plaster of Paris Powder and Hydrogel Beads
Get PDFPhosphorus released in lakes due to agricultural runoff causes eutrophication, deteriorating water quality and ecosystem harm. Adsorbing and recovering phosphorus could potentially contribute to a circular economy and reduce eutrophication. A literature review of phosphorus adsorbents was conducted to isolate for ideal adsorbents after defining criteria for surface water adsorption. Two adsorbents were studied for the removal of phosphate from water: plaster of Paris powder and hydrogel beads produced using alginate, carboxymethylcellulose, and aluminum. The reaction kinetics, adsorption capacity, and ability to desorb were compared. In deionised water, hydrogel beads had a maximum sorption capacity of 90.5 milligram phosphate per gram dry bead with an equilibration time of approximately 24 hours. In deionised water, plaster of Paris (POP) powder has a maximum capacity of 1.52 milligram phosphate per gram of powder with an equilibrium time of less than 10 minutes. Sorbents can potentially be reused following phosphate desorption, and desorbed phosphate may be reused as fertilizer
Trap and Treat in Situ Remediation Technologies: Reactive Gels and Emulsions
No full textThe goal of this thesis was to design new remedial methods that could be injected directly into the subsurface to contain (i.e. trap) and treat common groundwater contaminants (dyes, chlorinated compounds, and hydrocarbons) in situ. Injectable barriers were developed to trap contaminants using biobased materials, including zein, hydroxyethyl cellulose, chitosan, and edible mushrooms. By combining these materials with fillers or gelators (i.e.. carbon particles, salts, acids, enzymes, or oxidizers), barriers were either produced or enhanced. Barriers ranged from impermeable to semi-permeable and were either reactive or non-reactive. In addition to pollution containment, technologies were also developed to degrade contaminants. These methods include pump and treat via surfactant-flushing, surfactant-enhanced air sparging, bioremediation using Pseudomonas aeruginosa, enzymatic degradation by laccase, and chemical degradation by either oxidizing emulsifiers or zero-valent magnesium. Overall, this thesis is a proof of concept that our new remediation technologies could be applied in industry to both safely contain and remove common groundwater pollutants
Impact of amphiphiles, water chemistry and co-contaminants on miscible contaminant mixing behaviour
No full textGroundwater is a critical resource currently threatened by the presence of miscible and immiscible organic contaminants. This thesis discusses the use of amphiphiles to remove miscible organic contaminants from groundwater as well as the impact of water chemistry and co-contaminants on miscible contaminant migration. Amphiphiles such as sorbitan esters, amphiphilic polymers as well as glycerol and sugar esters can be used to separate miscible contaminants such as THF and DMSO from water. Amphiphiles can induce separation by disrupting hydrogen bonds between miscible contaminants and water through preferential interactions with either. The separation kinetics are driven by the self- assembly of amphiphiles. Groundwater ions also influence the mixing behavior of miscible contaminants. For example, sulfates decrease the miscibility of sulfolane in water, foster its partitioning into immiscible co-pollutants (e.g., hydrocarbons) and its sorption onto clay resulting in impeded migration. These studies can be used to inform future treatment technologies.Natural Sciences and Engineering Research Council of Canad
Bio-Based Materials for Agricultural Applications
No full textAgricultural plastic waste is a growing global problem, with plastic production increasing 10% annually since the 1950’s. Two zein based bioplastics were developed to be implemented as biodegradable alternatives to polyethylene mulching films and HDPE plastic #2 horticulture pots. With 1.8 million tonnes of plastic mulch consumed in 2015, it is imperative that novel biodegradable improvements be developed. The moisture retention capabilities, degradation potential, and ability to facilitate plant growth of the zein mulching films and horticulture pots were compared to current industry materials. Additionally, ALG-CMC (ACMC) hydrogel bead field trials were conducted to determine their success in remediating phosphorous contamination in agricultural runoff. The ACMC beads have a capacity of 10.38 mg-PO43- /g dry, with 0.0184 mg/L able to be recovered and repurposed into additional nutrients in a circular economy process. Zein mulching films can be supplemented with ACMC beads to improve the reduction of contaminated runoff
Water Purification and Conditioning using Surfactants and Surfactant-like Molecules
No full textThis thesis investigates the use of amphiphiles to treat groundwater, surface water and aqueous industrial effluents polluted with hydrocarbons, ions, and water-miscible solvents, to enable water reuse. In the context of groundwater treatment, hydrocarbons were removed through two main methods: 1) Fenton’s reagents in conjunction with surfactants (to promote contact with the reagents) and 2) electrokinetic remediation, to draw hydrocarbons emulsified with a surfactant towards an electrode, where they were oxidized. In the context of surface water purification, amphiphilic herders were used to ‘herd’ oil slicks on model saline and freshwater, to facilitate removal. Moreover, separation was achieved between water and water miscible solvents in groundwater or industrial streams by utilizing amphiphilic molecules. Finally, model produced water generated during fracking was conditioned using sodium cocoyl glutamate, to enable its reuse to produce viscoelastic fracking fluids. Highly acidic wastewater was conditioned using sodium lauroyl lactylate, which mitigates corrosion.Natural Sciences and Engineering Research Council of CanadaOntario Ministry of Agriculture, Food and Rural Affairs2023-08-0
Polymeric Bio-Based Materials: from Plastic Alternatives to Water Purification
Get PDFThe goal of this thesis was to develop polymeric materials using bio-based sources and methods that reduce both the use of toxic reagents in their production as well as the negative environmental impact of the finished product. Elastic and flexible materials were prepared using epoxidized soybean oil, citric acid, and varying amounts of epoxidized oleic acid allowing for the control of mechanical properties. The corn protein zein was chemically modified and combined with tomato cutin to produce hydrophobic flexible films. Acrylamide was polymerized by way of high voltage atmospheric cold plasma without the use of chemical initiators. Sodium alginate and bentonite clay were combined to prepare composite sorbents for Cu2+ and Zn2+ removal from water. The materials produced in this thesis show that bio-based polymeric materials are possible substitutes to some common polymers made using petrochemicals or as sorbents for the removal of unwanted metal ions from water.Natural Sciences and Engineering Research Council of CanadaOntario Ministry of Agriculture, Food and Rural AffairsBarret Family Foundatio
Iron Particle Attachment onto Model Geological Substrates
Get PDFFresh and aged iron particle attachment onto model mineral surfaces was studied using atomic force microscopy based – force spectroscopy (AFM) in different water chemistries as well as in the presence of surface modifiers for the particles (carboxymethyl cellulose polymer). The forces of interactions measured with AFM were explained in terms of classical DLVO forces (electrostatic, Born and van der Waals forces) as well as hydration, steric and magnetic forces, which are not accounted for by classical models. Theoretical interpretation of the results was thus performed using extended models, in which such interactions were considered. In the absence of surface modifiers, iron particle attachment onto silicates and iron oxides appeared favorable in pure water and salt solutions at pH 4 and 5.5, but was hindered in water amended with humic acids. Attachment of bare CIP was also unfavourable at pH 8, except in the presence of CaCl2 salt at 100 mM concentrations. Attachment between iron particles and iron oxides was favorable even in the presence of polymeric coatings. Conversely, in all solutions such coatings contributed to electro-steric repulsion between particles and silicates, which dominated over attractive van der Waals forces, albeit to a lesser extent in the presence of salts. To best assess the role of polymeric coatings in particle attachment, polymer sorption onto the model mineral surfaces considered was investigated using a Quartz Crystal Microbalance with Dissipation Monitoring. The results obtained confirmed the AFM findings, and furnished insights regarding the role of salts on polymer sorption onto substrates. Finally, the effect of aging on attachment was probed both by AFM and by analyzing cementation phenomena of iron aggregates using scanning electron microscopy, as well as by probing changes in particle compositional properties with various spectroscopy tools. The major effect of aging was to promote the formation of large cemented aggregates, which did not appear prone to disruption or remobilization.Ph
Polymeric Fluids for In Situ Remediation of Hexavalent Chromium Using Trap and Treat Technology
No full textHexavalent chromium (Cr(VI)) contamination is hazardous to the surrounding environment as well as posing chronic and acute health risks, emphasizing the importance of remediation methods that are cost-effective, environmentally friendly, and effective. Due to the rapid mobility of Cr(VI) in the subsurface, simultaneously immobilizing and treating the contaminant is of great importance. In this work, the natural polymers scleroglucan, xanthan, guar, and carboxymethyl cellulose (CMC), as well as the reducing agent sodium thiosulfate, were used to produce water-based polymeric fluids to simultaneously trap and treat Cr(VI) in the subsurface. The reduction, immobilization, and transport mechanisms were analyzed through batch tests, shear rheology, mechanical compression tests, microfluidic tests, and QCM-D experiments, proving the proposed remediation technology effective at simultaneously immobilizing and reducing Cr(VI), both with and without the presence of humic acids (HA), naturally occurring in situ
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
