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Tailoring the surface area and the acid-base properties of ZrO₂ for biodiesel production from Nannochloropsis sp.

ABSTRACT: Bifunctional heterogeneous catalysts have a great potential to overcome the shortcomings of homogeneous and enzymatic catalysts and simplify the biodiesel production processes using low-grade, high-free-fatty-acid feedstock. In this study, we developed ZrO₂-based bifunctional heterogeneous catalysts for simultaneous esterification and transesterification of microalgae to biodiesel. To avoid the disadvantage of the low surface area of ZrO₂, the catalysts were prepared via a surfactant-assisted sol-gel method, followed by hydrothermal treatments. The response surface methodology central composite design was employed to investigate various factors, like the surfactant/Zr molar ratio, pH, aging time, and temperature on the ZrO₂ surface area. The data were statistically analyzed to predict the optimal combination of factors, and further experiments were conducted for verification. Bi₂O₃ was supported on ZrO₂ via the incipient wetness impregnation method. The catalysts were characterized by a variety of techniques, which disclosed that the surfactant-assisted ZrO₂ nanoparticles possess higher surface area, better acid-base properties, and well-formed pore structures than bare ZrO₂. The highest yield of fatty acid methyl esters (73.21%) was achieved using Bi₂O₃/ZrO_2(CTAB), and the catalytic activity of the developed catalysts was linearly correlated with the total densities of the acidic and basic sites. The mechanism of the simultaneous reactions was also discussed.

SUBMITTER: Rahman NJA

PROVIDER: S-EPMC6838316 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Project description:Biological tissues at articulating surfaces, such as articular cartilage, typically have remarkable low-friction properties that limit tissue shear during movement. However, these frictional properties change with trauma, aging, and disease, resulting in an altered mechanical state within the tissues. Yet, it remains unclear how these surface changes affect the behaviour of embedded cells when the tissue is mechanically loaded. Here, we developed a cytocompatible, bilayered hydrogel system that permits control of surface frictional properties without affecting other bulk physicochemical characteristics such as compressive modulus, mass swelling ratio, and water content. This hydrogel system was applied to investigate the effect of variations in surface friction on the biological response of human articular chondrocytes to shear loading. Shear strain in these hydrogels during dynamic shear loading was significantly higher in high-friction hydrogels than in low-friction hydrogels. Chondrogenesis was promoted following dynamic shear stimulation in chondrocyte-encapsulated low-friction hydrogel constructs, whereas matrix synthesis was impaired in high-friction constructs, which instead exhibited increased catabolism. Our findings demonstrate that the surface friction of tissue-engineered cartilage may act as a potent regulator of cellular homeostasis by governing the magnitude of shear deformation during mechanical loading, suggesting a similar relationship may also exist for native articular cartilage.Statement of significanceExcessive mechanical loading is believed to be a major risk factor inducing pathogenesis of articular cartilage and other load-bearing tissues. Yet, the mechanisms leading to increased transmission of mechanical stimuli to cells embedded in the tissue remain largely unexplored. Here, we demonstrate that the tribological properties of loadbearing tissues regulate cellular behaviour by governing the magnitude of mechanical deformation arising from physiological tissue function. Based on these findings, we propose that changes to articular surface friction as they occur with trauma, aging, or disease, may initiate tissue pathology by increasing the magnitude of mechanical stress on embedded cells beyond a physiological level.

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Tailoring the surface area and the acid-base properties of ZrO₂ for biodiesel production from Nannochloropsis sp.

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OmicsDI is part of the ELIXIR infrastructure

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Tailoring the surface area and the acid-base properties of ZrO2 for biodiesel production from Nannochloropsis sp.

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OmicsDI is part of the ELIXIR infrastructure

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Tailoring the surface area and the acid-base properties of ZrO₂ for biodiesel production from Nannochloropsis sp.