Hybrid Solar Photoelectro-Fenton and Ozone Processes for the Sustainable Removal of COVID-19 Pharmaceutical Contaminants

At a Glance

Metadata	Details
Publication Date	2025-10-10
Journal	Processes
Authors	Sonia Herrera-Chávez, Martín Pacheco‐Álvarez, Luis A. Godı́nez, Enric Brillas, Juan M. Peralta‐Hernández
Institutions	Universidad de Guanajuato, Tecnológico Nacional de México
Analysis	Full AI Review Included

Executive Summary

This research demonstrates the high efficiency and sustainability of a hybrid solar photoelectro-Fenton (SPEF) system coupled with ozonation (O₃) for the pilot-scale removal of pharmaceutical contaminants related to COVID-19 treatment.

Core Value Proposition: The hybrid SPEF/O₃ system provides a scalable, sustainable, and highly effective Advanced Oxidation Process (EAOP) for treating complex water matrices contaminated with recalcitrant pharmaceuticals, leveraging abundant solar energy.
Model Pollutant Performance: Complete degradation (100%) of paracetamol (20 mg L^-1) was achieved in approximately 50 min using the SPEF process under optimal conditions (j = 60 mA cm^-2).
Mineralization Efficiency: The SPEF process achieved a significant 78% Chemical Oxygen Demand (COD) reduction for paracetamol within 90 min, confirming high mineralization capacity despite the formation of persistent intermediates (catechol, phenol).
Energy Consumption: The process demonstrated a low specific energy consumption (EC_COD) of 0.0519 kWh (g COD)^-1, highlighting its economic viability compared to traditional EAOPs.
Hybrid System Performance: When treating a four-drug mixture (dexamethasone, paracetamol, amoxicillin, azithromycin), the SPEF/O₃ system significantly outperformed standalone O₃/sunlight, achieving nearly 60% total drug degradation and 41% COD abatement in 180 min.
Technology Readiness: The pilot plant utilizes commercially available components (BDD electrodes, CPC photoreactors, ozone generator), enhancing its potential for replication and large-scale implementation in developing countries.

Technical Specifications

Parameter	Value	Unit	Context
Reactor Type	CPC Photoreactor	N/A	Compound Parabolic Collector
Working Volume	30	L	Total solution volume
Electrode Configuration	BDD/BDD	N/A	Boron-Doped Diamond (Anode/Cathode)
Electrode Area	64	cm²	Geometric area (each electrode)
Optimal Current Density (j)	60	mA cm^-2	Selected for SPEF trials
Electrolysis Time (Standard)	90	min	Based on solar irradiance profile
UV-A Irradiance (Natural)	30-35	W m^-2	Measured during summer trials
Operating Temperature	27	°C	Controlled via heat exchangers
Supporting Electrolyte	0.05	M	Na₂SO₄
Fenton Catalyst	0.5	mM	Fe²⁺
Optimal pH	3.0	N/A	Required for Fenton chemistry
H₂O₂ Accumulation (Max)	~3.0	mM	Achieved at j = 60 mA cm^-2
Paracetamol Initial Concentration	20 or 50	mg L^-1	Model pollutant concentration
Mixture Initial Concentration (Total)	116.25	mg L^-1	Sum of 4 drugs (Dexamethasone, Paracetamol, Amoxicillin, Azithromycin)
Paracetamol Degradation	100	%	Achieved in ~50 min (SPEF)
Paracetamol COD Removal	78	%	Achieved in 90 min (SPEF)
Specific Energy Consumption (EC_COD)	0.0519	kWh (g COD)^-1	SPEF process at 90 min
Mixture Degradation (SPEF/O₃)	Nearly 60	%	Total drug concentration (180 min)
Mixture COD Abatement (SPEF/O₃)	41	%	Total COD (180 min)

Key Methodologies

Pilot Plant Setup: A continuous flow system was constructed using a 30 L reservoir, a centrifugal pump (300 L h^-1 flow rate), a filter-press electrochemical cell (BDD/BDD electrodes), a 15 L CPC-type photoreactor (DURAN® glass tubes), and an ozone generator (7 L min^-1 maximum capacity).
Electrode Pretreatment: BDD electrodes were activated by applying a high current density (100 mA cm^-2) in 0.05 M Na₂SO₄ solution for 120 min to ensure optimal electrochemical performance.
SPEF Operating Conditions: Experiments were run at pH 3.0, maintained by H₂SO₄, using 0.05 M Na₂SO₄ as the supporting electrolyte and 0.5 mM Fe²⁺ as the catalyst. A constant current density of 60 mA cm^-2 was applied for 90 min under natural solar irradiation.
H₂O₂ Electrogeneration: Hydrogen peroxide was continuously generated in situ at the BDD cathode via oxygen reduction, facilitated by the cascade water flow ensuring oxygen saturation.
SPEF/O₃ Hybridization: For mixture trials, the SPEF process was combined with continuous ozone gas bubbling (5 L min^-1 flow rate) introduced via a glass diffuser into the CPC photoreactor.
Analytical Characterization:
- Drug concentrations and aromatic intermediates (catechol, phenol) were quantified using High-Performance Liquid Chromatography (HPLC) with a Supelco C18 column and UV detection at 245 nm.
- H₂O₂ accumulation and Faradaic efficiency were determined by UV-Vis titration with titanium (IV) oxysulfate.
- Mineralization extent and energy consumption were calculated based on Chemical Oxygen Demand (COD) assays.

Commercial Applications

The hybrid solar photoelectro-Fenton (SPEF/O₃) technology, relying on BDD electrodes and solar energy, is highly relevant for sustainable water remediation across several sectors:

Municipal Wastewater Treatment: Effective removal of Contaminants of Emerging Concern (CECs), particularly persistent pharmaceuticals and antibiotics, ensuring cleaner discharge into surface waters.
Pharmaceutical Manufacturing Effluent: High-efficiency degradation of complex, high-concentration drug mixtures that are recalcitrant to conventional biological treatment.
Decentralized Water Remediation: The use of solar energy and CPC photoreactors makes this technology ideal for deployment in remote or developing regions where grid power is limited, promoting sustainable water reuse.
Advanced Oxidation Processes (AOPs) Integration: Provides a robust, synergistic alternative to standalone ozonation or UV-based AOPs, offering enhanced mineralization and reduced energy costs due to solar assistance.
BDD Electrode Technology: Confirms the viability and robustness of BDD electrodes in pilot-scale EAOPs for generating powerful oxidizing species (hydroxyl radicals) over extended operational periods.

View Original Abstract

This study explores a hybrid advanced electrochemical oxidation process (EAOP) intensified by solar irradiation and ozone for the treatment of wastewater containing COVID-19-related pharmaceuticals. Pilot-scale trials were performed in a 30 L compound parabolic collector (CPC)-type photoreactor with a boron-doped diamond (BDD-BDD) electrode configuration. Under optimal conditions (50 mg L−1 paracetamol, 0.05 M Na2SO4, 0.50 mM Fe2+, pH 3.0, and 60 mA cm−2), the solar photoelectro-Fenton (SPEF) process achieved 78% chemical oxygen demand (COD) reduction within 90 min, with catechol and phenol detected as the main aromatic intermediates. When applied to a four-drug mixture (dexamethasone, paracetamol, amoxicillin, and azithromycin), the solar photoelectro-Fenton (SPEF-ozone (O3)) system reached 60% degradation and 41% COD removal under solar conditions. The results highlight the synergistic effect of ozone and solar energy in enhancing the electrochemical oxidation process (EAOP) performance and demonstrate the potential of these processes for scalable and sustainable removal of pharmaceutical contaminants from wastewater.

Tech Support

Original Source

DOI: https://doi.org/10.3390/pr13103234

References

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