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Cavitation intensifying bags improve ultrasonic advanced oxidation with Pd/Al₂O₃ catalyst.

ABSTRACT: Advanced oxidation processes can potentially eliminate organic contaminants from industrial waste streams as well as persistent pharmaceutical components in drinking water. We explore for the first time the utilization of Cavitation Intensifying Bags (CIB) in combination with Pd/Al₂O₃ catalyst as possible advanced oxidation technology for wastewater streams, oxidizing terephthalic acid (TA) to 2-hydroxyterephthalic acid (HTA). The detailed characterization of this novel reaction system reveals that, during sonication, the presence of surface pits of the CIB improves the reproducibility and thus the control of the sonication process, when compared to oxidation in non-pitted bags. Detailed reaction kinetics shows that in the CIB reactor the reaction order to TA is zero, which is attributed to the large excess of TA in the system. The rate of HTA formation increased ten-fold from ~0.01 ?M*min^-1 during sonication in the CIB, to ~0.10 ?M*min^-1 for CIB in the presence of the Pd/Al₂O₃ catalyst. This enhancement was ascribed to a combination of improved mass transport, the creation of thermal gradients, and Pd/Al₂O₃ catalyst near the cavitating bubbles. Further analysis of the kinetics of HTA formation on Pd/Al₂O₃ indicated that initially the reaction underwent through an induction period of 20 min, where the HTA concentration was ~0.3 ?M. After this, the reaction rate increased reaching HTA concentrations ~6 ?M after 40 min. This behavior resembled that observed during oxidation of hydrocarbons on metal catalysts, where the slow rate formation of hydroperoxides on the metal surface is followed by rapid product formation upon reaching a critical concentration. Finally, a global analysis using the Intensification Factor (IF) reveals that CIB in combination with the Pd/Al₂O₃ catalyst is a desirable option for the oxidation of TA when considering increased oxidation rates and costs.

SUBMITTER: Pappaterra M

PROVIDER: S-EPMC7786540 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Cavitation intensifying bags improve ultrasonic advanced oxidation with Pd/Al2O3 catalyst.

Pappaterra Maria M Xu Pengyu P van der Meer Walter W Faria Jimmy A JA Fernandez Rivas David D

Ultrasonics sonochemistry 20200907

Advanced oxidation processes can potentially eliminate organic contaminants from industrial waste streams as well as persistent pharmaceutical components in drinking water. We explore for the first time the utilization of Cavitation Intensifying Bags (CIB) in combination with Pd/Al2O3 catalyst as possible advanced oxidation technology for wastewater streams, oxidizing terephthalic acid (TA) to 2-hydroxyterephthalic acid (HTA). The detailed characterization of this novel rea ...[more]

PMID: 32947211

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Project description:Highlights • Vortex based hydrodynamic cavitation was shown to enhance rate of extraction from macroalgae by an order of magnitude.• Per-pass extraction factor was found to be proportional to the mass fraction of product in macroalgae.• Pressure drop of 200 kPa was found to exhibit maximum rate of extraction within the considered range (50–300 kPa)• Energetic productivity (kg of product/kJ) was found to decrease steeply with increase in number of passes beyond 100. Macroalgae have a tremendous potential to become an important renewable resource for valuable biomolecules and chemicals. New and improved ways of cell disruption and of enhancing rate as well as yield of extraction of valuable products from macroalgae are needed to fully realise this potential. In this work, hydrodynamic cavitation (HC) was used for intensifying rate and yield of extraction of phycoerythrin, proteins and carbohydrates from marine macroalgae Palmaria palmata. We use vortex-based HC devices which do not use small restrictions like orifice-based HC devices or moving parts like rotor–stator based HC devices. A bench scale setup with a nominal slurry flow rate of 20 LPM was established. Dried and powdered macroalgae was used. Influence of key operating parameters like pressure drop and number of passes on extraction performance (the rate and yield) was measured. A simple, yet effective model was developed and used for interpreting and describing experimental data. The results indicate that there exists an optimum pressure drop across the device at which extraction performance is maximum. The extraction performance with HC was found to be significantly better than the stirred vessels. HC has resulted in 2 to 20 times improvement in the rate of extraction of phycoerythrin (R-PE), proteins and carbohydrates. Based on the results obtained in this work, pressure drop of 200 kPa and number of passes through the HC devices of about 100 were found to be most effective for HC-assisted intensified extraction from macroalgae. The presented results and model will be useful for harnessing vortex-based HC devices for intensifying the extraction of valuable products from macroalgae.

Dataset Information

Cavitation intensifying bags improve ultrasonic advanced oxidation with Pd/Al₂O₃ catalyst.

Publications

Cavitation intensifying bags improve ultrasonic advanced oxidation with Pd/Al<sub>2</sub>O<sub>3</sub> catalyst.

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