Treatment of limonene-polluted air streams by sequential GAC adsorption and electrochemically H2O2-based oxidation: Challenges and perspectives

Author(s)

Santos, Gessica O. S. ; Saez, Cristina ; Lanza, Marcos R. V. ; Rodrigo, Manuel A.

• Document type: Journal article
• Source: PROCESS SAFETY AND ENVIRONMENTAL PROTECTION; v. 197, p. 15-pg., 2025-05-01.

Abstract

The sequenced granular activated carbon (GAC)-oxidation process stands out as an advanced treatment that combines the adsorption ability of GAC to capture contaminants with a subsequent oxidation step to degrade or transform these pre-adsorbed into less toxic or added-value products. With this two-step treatment it is possible to extend GAC's service life and enhances process sustainability. However, research gap remains regarding its application for non-polar gaseous pollutants and the use of electrogenerated oxidants in the oxidation step. To address this, a case study was conducted using limonene (LIM), a non-polar, hydrophobic volatile organic compound common found in indoor air and industrial products. Here, LIM-polluted gaseous streams were treated using a fixed-bed setup, followed by oxidation with electrochemically produced hydrogen peroxide (H2O2). Initial tests showed that LIM in aqueous solutions was not efficiently degraded by H2O2 alone, but radical oxidation, promoted by H2O2 activation by UVC light or O3, improved reactivity. On GAC, H2O2 unexpectedly proved effective due to interactions with free radicals, though UVC irradiation provided minimal additional improvement. In contrast, the addition of ferrocene (Fc), a promising heterogeneous catalyst, significantly enhanced degradation, achieving removal efficiencies up to 35 % in neutral media. This improvement was attributed the Fc-mediated activation within GAC. Eight different intermediates were identified, supporting an oxidation mechanism that varies between technologies. Overall, characterization revealed minimal structural changes in GAC post-treatment. BET analysis showed slight surface area variations for UVC and Fc/H2O2 processes, but a decrease in 69 % for H2O2 alone, and a 24.4 % increase for UVC/H2O2. (AU)

• FAPESP's process: 22/03386-6 - Treatment of VOCs by a combined absorption and heterogeneous electron-Fenton using iron-modified cathodes
• Grantee: Géssica de Oliveira Santiago Santos
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 20/02743-4 - Fe/RuO2-TiO2 films supported on carbon felt for norfloxacin degradation by heterogeneous electro-fenton process
• Grantee: Géssica de Oliveira Santiago Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 22/12895-1 - Advanced processes for the degradation of emerging pollutants: catalytic materials, electroanalytical sensors and scientific dissemination
• Grantee: Marcos Roberto de Vasconcelos Lanza
• Support Opportunities: Research Projects - Thematic Grants