Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)

This study presents a sustainable approach for synthesizing high-performance activated carbon from <i>Spirulina</i> Alga through hydrothermal carbonization followed by chemical activation using potassium hydroxide. The resulting activated carbon exhibited a high Brunauer–Emmett–Teller (B...

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Main Authors: Dipendu Saha, Ryan Schlosser, Lindsay Lapointe, Marisa L. Comroe, John Samohod, Elijah Whiting, David S. Young
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Molecules
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Online Access:https://www.mdpi.com/1420-3049/30/13/2848
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author Dipendu Saha
Ryan Schlosser
Lindsay Lapointe
Marisa L. Comroe
John Samohod
Elijah Whiting
David S. Young
author_facet Dipendu Saha
Ryan Schlosser
Lindsay Lapointe
Marisa L. Comroe
John Samohod
Elijah Whiting
David S. Young
author_sort Dipendu Saha
collection DOAJ
description This study presents a sustainable approach for synthesizing high-performance activated carbon from <i>Spirulina</i> Alga through hydrothermal carbonization followed by chemical activation using potassium hydroxide. The resulting activated carbon exhibited a high Brunauer–Emmett–Teller (BET) surface area of 1747 m<sup>2</sup>/g and a total pore volume of 1.147 cm<sup>3</sup>/g, with micropore volume accounting for 0.4 cm<sup>3</sup>/g. Characterization using Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), and gas adsorption analyses confirmed the presence of hierarchical micro- and mesoporosity as well as favorable surface functional groups. The synthesized carbon was used to fabricate electrodes for membrane capacitive deionization (MCDI) along with cation and anion-selective membranes, which were then tested with saline water (500–5000 ppm) and synthetic hard water (898 ppm of total salts). The salt adsorption capacity (SAC) reached 25 (batch) to 40 (continuous) mg/g, while rapid adsorption rates with average salt adsorption rates (ASARs) values exceeding 10 (batch) to 30 (continuous) mg·g<sup>−1</sup>·min<sup>−1</sup> during early stages were obtained. Batch MCDI experiments demonstrated a higher SAC compared to continuous operation, with non-monotonic trends in SAC observed as a function of feed concentration. Ion adsorption kinetics were influenced by ion valency, membrane selectivity, and pore structure. The specific energy consumption (SEC) was calculated as 8–21 kJ/mol for batch and 0.1–0.5 kJ/mol for continuous process. These performance metrics are on par with or surpass those reported in the recent literature for similar single-electrode CDI configurations. The results demonstrate the viability of using Alga-derived carbon as an efficient and eco-friendly electrode material for water desalination technologies.
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spelling doaj-art-af939a8a23c14fb8905a5d7c7ad81a6f2025-07-11T14:41:13ZengMDPI AGMolecules1420-30492025-07-013013284810.3390/molecules30132848Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)Dipendu Saha0Ryan Schlosser1Lindsay Lapointe2Marisa L. Comroe3John Samohod4Elijah Whiting5David S. Young6Chemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAChemical and Materials Engineering Department, Widener University, 1 University Place, Chester, PA 19013, USAThis study presents a sustainable approach for synthesizing high-performance activated carbon from <i>Spirulina</i> Alga through hydrothermal carbonization followed by chemical activation using potassium hydroxide. The resulting activated carbon exhibited a high Brunauer–Emmett–Teller (BET) surface area of 1747 m<sup>2</sup>/g and a total pore volume of 1.147 cm<sup>3</sup>/g, with micropore volume accounting for 0.4 cm<sup>3</sup>/g. Characterization using Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), and gas adsorption analyses confirmed the presence of hierarchical micro- and mesoporosity as well as favorable surface functional groups. The synthesized carbon was used to fabricate electrodes for membrane capacitive deionization (MCDI) along with cation and anion-selective membranes, which were then tested with saline water (500–5000 ppm) and synthetic hard water (898 ppm of total salts). The salt adsorption capacity (SAC) reached 25 (batch) to 40 (continuous) mg/g, while rapid adsorption rates with average salt adsorption rates (ASARs) values exceeding 10 (batch) to 30 (continuous) mg·g<sup>−1</sup>·min<sup>−1</sup> during early stages were obtained. Batch MCDI experiments demonstrated a higher SAC compared to continuous operation, with non-monotonic trends in SAC observed as a function of feed concentration. Ion adsorption kinetics were influenced by ion valency, membrane selectivity, and pore structure. The specific energy consumption (SEC) was calculated as 8–21 kJ/mol for batch and 0.1–0.5 kJ/mol for continuous process. These performance metrics are on par with or surpass those reported in the recent literature for similar single-electrode CDI configurations. The results demonstrate the viability of using Alga-derived carbon as an efficient and eco-friendly electrode material for water desalination technologies.https://www.mdpi.com/1420-3049/30/13/2848porous carbonadsorptioncapacitive deionizationwater purification
spellingShingle Dipendu Saha
Ryan Schlosser
Lindsay Lapointe
Marisa L. Comroe
John Samohod
Elijah Whiting
David S. Young
Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
Molecules
porous carbon
adsorption
capacitive deionization
water purification
title Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
title_full Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
title_fullStr Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
title_full_unstemmed Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
title_short Nanoporous Carbons from Hydrothermally Treated Alga: Role in Batch and Continuous Capacitive Deionization (CDI)
title_sort nanoporous carbons from hydrothermally treated alga role in batch and continuous capacitive deionization cdi
topic porous carbon
adsorption
capacitive deionization
water purification
url https://www.mdpi.com/1420-3049/30/13/2848
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