In the space of just a few years, nanotechnology has become a topical subject not only in academia, but also in the daily lives of people. These results provided critical information about the colloidal properties of the new TiO2-graphene nanocomposites and were useful in predicting the fate and transport of TiO2-graphene nanocomposites in natural water environments. However, prolonged UV irradiation may stabilize the nanoparticles. A known intensity of UV irradiation was beneficial in the formation of TiO2-graphene nanoparticle aggregates. The stability of this composite nanoparticles was between those of pure TiO2 and graphene. The calculated Hamaker constant of the TiO2-graphene nanocomposites in aqueous solution prepared in the lab was 2.31×10(-20)J. TiO2-graphene nanoparticles were significantly aggregated in the presence of a diavalent cation compared with monovalent cation because the former was more capable of effective charge screening and neutralization. The aggregation of TiO2-graphene nanoparticles in aqueous media followed the colloidal theory. The zeta potentials and hydrodynamic diameter of the nanoparticles were used as bases to assess the aggregation behavior, and stability of nanocomposites exposed to UV irradiation was expressed in terms of supernatant concentration. The aggregation kinetics of TiO2-graphene nanocomposites in aqueous solution affected by solution pH, salt types (NaCl, CaCl2) and concentrations of electrolytes, and stability induced by UV irradiation was investigated in this study. Our findings show that pyrolysis temperature used for biochar production had a large effect on the aggregation of biochar colloids in the aqueous environment and that cation type and dissolved natural organic matter are controlling variables. The aggregation of biochar colloids was accelerated by HA with the concentration higher than 5 mg L-1 through cation-bridging while the aggregation was inhibited in the presence of <2.5 mg L-1 HA. In CaCl2 solutions with high salt concentrations (near to the CCCs), different HA concentrations caused distinct effects on the aggregation of biochar colloids. HA of 5 mg L-1 greatly increased the CCCs of WB300 and WB600 colloids to 1288 and 806 mM in NaCl solutions, but decreased the CCCs to 54.6 and 37.0 mM in CaCl2 solutions because of strong bridging between HA and Ca2+. WB300 had more oxygen-containing functional groups than WB600, which induced more negative surface charge on WB300. Results show that the critical coagulation concentrations (CCCs) of WB300 colloids in NaCl and CaCl2 solutions were 274 and 61.4 mM, which were higher than those (183 mM for NaCl and 38.1 mM for CaCl2) of WB600 colloids. The aggregation kinetics of wheat straw-derived biochar colloids pyrolyzed at two temperatures 300 and 600 ☌ (WB300 and WB600 colloids, respectively) were investigated in monovalent and divalent electrolyte solutions in absence/presence of humic acid (HA). This webinar will provide a brief introduction to these techniques, then several case studies will be presented that utilized dynamic light scattering ( DLS), multi-angle light scattering with size-exclusion chromatography ( SEC-MALS), and composition-gradient multi-angle light scattering ( CG-MALS) as analytical tools for the characterization and formulation of macromolecules ranging from virus-like particle-based vaccines to monoclonal antibodies.An understanding of biochar colloid aggregation and stability in aqueous environments is critical for assessing biochar fate and mobility in the soil. Some of the most important tools for analyzing the properties and behavior of biologics are based on multi-angle light scattering and dynamic light scattering, which directly determine molar mass, size, stability and interactions. Given the complexity of biological macromolecules used for therapeutic purposes, detailed characterization is both essential and challenging. Presented by: Ozan Kumru, Ph.D., University of Kansas Vaccine Analytics and Formulation Center, and Dan Some, Ph.D., Wyatt Technology Dynamic & Electrophoretic Light Scattering.
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