Characterization of Lignin

Lignin is a complex organic compound crucial to the structural tissues of vascular plants, such as trees. The cyclic structure and aromaticity of lignin give it significant potential to be used as a renewable and safe replacement for toxic aromatic compounds in chemical and industrial processes. The purpose of this experiment was to characterize lignin, specifically the particle diameter and zeta potential, using both the Zetasizer Nano ZSP and the ImageJ image processing software, and to compare the accuracy of both measurement methods. Due to the natural fluorescence of lignin, a fluorescence microscope is used to capture images of lignin particles. By having a known distance and the scale of measurement, with ImageJ it is possible to calculate distances, such as the diameters of particles in images. The Zetasizer Nano ZSP is a device capable of measuring both particle diameter and zeta potential, which is the electrical charge existing on particles suspended in a medium. Small amounts of lignin, in powder form, are placed into scintillation vials with different amounts of distilled water to create 3 different concentrations of sample to measure using the Zetasizer. Between 10-15mL of sample are placed into specialized measurement cells and put into the Zetasizer. Multiple measurements are conducted and averaged to achieve accurate results. The measured zeta potential value is indicative of the stability of the lignin. If the value of zeta potential is higher than 30mV, negative or positive, it has a high stability and low reactivity. The average values of zeta potential measured by the Zetasizer ranged from -27mV to -21mV. The particle diameter is important in characterization, as the smaller and more distributed the particles are, there is a larger surface area for reactions to occur. Average particle diameter measured by the Zetasizer ranged from 926-976µm. The results from the Zetasizer Nano ZSP are more accurate than those from the ImageJ software, as ImageJ allows for a substantial amount of human error to impact the results. The outcomes help direct future experiments using lignin and beneficial to future research concerning lignin and its potential

Development of advanced nanocomposite membranes using graphene nanoribbons and nanosheets for water treatment

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.memsci.2018.04.034 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Water-intensive industries have to comply with stringent environmental regulations and evolving regulatory frameworks requiring the development of new technologies for water recycling. Development of polymeric membranes may provide an effective solution to improve water recycling, but require finely-tuned pore size and surface chemistry for ionic and molecular sieving to be efficient. Additionally, fouling is a major challenge that limits the practical application of the membranes in water recycling in these industries. In this work, four different graphene oxide (GO) derivatives were incorporated into a polyethersulfone (PES) matrix via a non-solvent induced phase separation (NIPS) method. The GO derivatives used have different shapes (nanosheets vs nanoribbons) and different oxidation states (C/O = 1.05–8.01) with the potential to enhance water flux and suppress fouling of the membranes through controlled pore size, hydrophilicity, and surface charge. The permeation properties of the PES/GO membranes were evaluated using a water sample from the Athabasca oil sands of Alberta. The results for contact angle and streaming potential measurements indicate the formation of more hydrophilic and negatively charged PES/GO nanocomposite membranes. All graphene-based nanocomposite membranes demonstrated better water flux and rejection of organic matter compared to the unmodified PES membrane. The fouling measurement results revealed that fouling was impeded due to enhanced membrane surface properties. Longitudinally unzipped graphene oxide nanoribbons (GONR-L) at an optimum loading of 0.1 wt% (wt%) provided the maximum water flux (70 LMH at 60 psi), organic matter rejection (59%) and antifouling properties (30% improvement compared to pristine PES membrane). Flux recovery ratio experiments indicated a remarkable enhancement in the fouling resistance property of PES/GO nanocomposite membranes.Natural Sciences and Engineering Research Council of Canada [33413]Natural Resources Canada [32462]Suncor Energy IncorporatedConocoPhillipsUniversity of WaterlooDevon Canad

Multi-objective reinforcement learning for self-optimization of flow chemistry [Abstract]

Multi-objective reinforcement learning for self-optimization of flow chemistry [Abstract]</p

Thermal graphene metamaterials and epsilon-near-zero high temperature plasmonics

The key feature of a thermophotovoltaic (TPV) emitter is the enhancement of thermal emission corresponding to energies just above the bandgap of the absorbing photovoltaic cell and simultaneous suppression of thermal emission below the bandgap. We show here that a single layer plasmonic coating can perform this task with high efficiency. Our key design principle involves tuning the epsilon-near-zero frequency (plasma frequency) of the metal acting as a thermal emitter to the electronic bandgap of the semiconducting cell. This approach utilizes the change in reflectivity of a metal near its plasma frequency (epsilon-near-zero frequency) to lead to spectrally selective thermal emission and can be adapted to large area coatings using high temperature plasmonic materials. We provide a detailed analysis of the spectral and angular performance of high temperature plasmonic coatings as TPV emitters. We show the potential of such high temperature plasmonic thermal emitter coatings (p-TECs) for narrowband near-field thermal emission. We also show the enhancement of near-surface energy density in graphene-multilayer thermal metamaterials due to a topological transition at an effective epsilon-near-zero frequency. This opens up spectrally selective thermal emission from graphene multilayers in the infrared frequency regime. Our design paves the way for the development of single layer p-TECs and graphene multilayers for spectrally selective radiative heat transfer applications.Comment: 10 pages, 8 figure