Achieving Electrochemical-Sustainable-Based Solutions for Monitoring and Treating Hydroxychloroquine in Real Water Matrix

At a Glance

Metadata	Details
Publication Date	2022-01-11
Journal	Applied Sciences
Authors	Danyelle Medeiros de Araújo, Elisama Vieira dos Santos, Carlos A. Martínez‐Huitle, Achille De Battisti
Institutions	Universidade Federal do Rio Grande do Norte, University of Ferrara
Citations	14
Analysis	Full AI Review Included

Executive Summary

This research focuses on integrating electrochemical technologies to achieve Sustainable Development Goal 6 (SDG6) by monitoring and eliminating Hydroxychloroquine (HCQ) from real river water matrices.

Value Proposition: Demonstrated an efficient, integrated system combining low-cost sensing and advanced oxidation for the detection and complete removal of HCQ, a persistent pharmaceutical pollutant.
Sensing Technology: A cork-graphite composite sensor was developed and validated using Differential Pulse Voltammetry (DPV), proving effective for HCQ quantification in complex real water matrices with minimal interference.
Detection Performance: The sensor achieved a Limit of Detection (LOD) of 1.46 mg L^-1 (3.36 µM) and a Limit of Quantification (LOQ) of 4.42 mg L^-1 (10.19 µM).
Treatment Technology: Electrochemical Oxidation (EO) was performed using Boron Doped Diamond (BDD) anodes, leveraging their capacity for efficient electrogeneration of heterogeneous hydroxyl (•OH) radicals.
Removal Efficiency: Complete HCQ decay was achieved within 90 minutes at all tested current densities (15, 30, and 45 mA cm^-2).
Mineralization Results: Significant organic matter removal, measured by Chemical Oxygen Demand (COD), reached up to 84% at the highest current density (45 mA cm^-2).
Kinetic Behavior: HCQ decay followed pseudo-first-order kinetics, with the reaction rate accelerating proportionally to the applied current density.

Technical Specifications

Parameter	Value	Unit	Context
Initial HCQ Concentration	26.7	mg L^-1	Polluted river water sample
Sensor Composition	70:30	% w/w	Cork powder:Graphite powder
Sensor Binder Volume	0.3	mL	Paraffin oil
Sensor Limit of Detection (LOD)	1.46 (3.36)	mg L^-1 (µM)	DPV analysis in river water
Sensor Limit of Quantification (LOQ)	4.42 (10.19)	mg L^-1 (µM)	DPV analysis in river water
BDD Anode Boron Content	500	mg L^-1	BDD electrode specification
BDD Diamond Layer Thickness	2.68	µm	BDD electrode specification
BDD sp³/sp² Ratio	225	-	BDD electrode specification
Applied Current Densities (j)	15, 30, 45	mA cm^-2	Galvanostatic EO treatment
Maximum EO Time	120	min	Duration of electrolysis experiments
Reactor Volume	250	mL	Undivided batch reactor
Supporting Electrolyte	0.1	M	H₂SO₄ (used for acidification)
Maximum COD Removal	84	%	Achieved at 45 mA cm^-2
HCQ Decay Rate Constant (k)	0.118	min^-1	Pseudo-first order, achieved at 45 mA cm^-2
Oxygen Evolution Potential	+1.85	V vs Ag/AgCl (3 M)	Non-polluted water, BDD anode

Key Methodologies

The study involved two main phases: sensor development/quantification and electrochemical treatment.

Cork-Graphite Sensor Fabrication:
- Raw cork granules were processed to a powder fraction below 150 µm.
- The composite was prepared by mechanically homogenizing 70% cork powder and 30% graphite (w/w) with 0.3 mL of paraffin oil binder for 30 minutes.
- The resulting composite served as the working electrode (geometric area 0.45 mm²).
HCQ Quantification (DPV):
- Measurements were conducted using Differential Pulse Voltammetry (DPV) in a three-electrode cell (cork-graphite WE, Pt AE, Ag/AgCl RE).
- The analytical curve was constructed using non-polluted river water spiked with HCQ (2.5 to 40 mg L^-1) to assess matrix effects.
- HCQ concentration in the polluted sample was determined using the standard addition method to mitigate matrix interference effects.
Electrochemical Oxidation (EO) Setup:
- Experiments were performed in an undivided 250 mL batch reactor with magnetic stirring.
- The anode was Boron Doped Diamond (BDD) and the cathode was Titanium (Ti), separated by approximately 2 cm.
- The polluted river water sample (250 mL) was acidified with 10 mL of 0.1 M H₂SO₄ supporting electrolyte.
Galvanostatic Treatment:
- Constant current densities (j) of 15, 30, and 45 mA cm^-2 were applied for a maximum duration of 120 minutes.
- HCQ decay was monitored in real-time using the DPV cork-graphite sensor.
- Overall organic matter removal was tracked by measuring Chemical Oxygen Demand (COD) at predetermined intervals.
Kinetic and Efficiency Analysis:
- Decay kinetics were analyzed assuming a pseudo-first-order reaction model, confirming that the reaction rate increased with higher applied current density.
- Total Current Efficiency (%TCE) and Energy Consumption (EC) were calculated based on COD removal data to evaluate the viability and cost of the EO process.

Commercial Applications

The integrated technologies developed in this study are highly relevant for environmental engineering and water management sectors, particularly those focused on emerging contaminants.

Advanced Water Treatment (AWT): Utilizing BDD-based Electrochemical Oxidation (EO) for the tertiary treatment of municipal and industrial wastewater, specifically targeting refractory organic micropollutants (pharmaceuticals, pesticides) that resist conventional biological methods.
Environmental Monitoring and Sensing: Deployment of low-cost, robust cork-graphite composite sensors for decentralized, real-time monitoring of pharmaceutical contamination (like HCQ) in surface water bodies (rivers, lakes, lagoons).
Sustainable Water Solutions (SDG6): Implementation of integrated EO systems in developing regions where conventional treatment infrastructure is limited, providing effective, scalable solutions for clean water and sanitation.
Process Control and Optimization: Using the DPV sensor for rapid, in-situ feedback on pollutant concentration during EO treatment, allowing for dynamic adjustment of current density to optimize energy consumption and treatment time.
Electrode Manufacturing (BDD): The high performance of the BDD anode confirms its commercial viability for high-efficiency electrochemical reactors used in water decontamination, supporting the market for advanced electrode materials.

View Original Abstract

Hydroxychloroquine (HCQ) has been extensively consumed due to the Coronavirus (COVID-19) pandemic. Therefore, it is increasingly found in different water matrices. For this reason, the concentration of HCQ in water should be monitored and the treatment of contaminated water matrices with HCQ is a key issue to overcome immediately. Thus, in this study, the development of technologies and smart water solutions to reach the Sustainable Development Goal 6 (SDG6) is the main objective. To do that, the integration of electrochemical technologies for their environmental application on HCQ detection, quantification and degradation was performed. Firstly, an electrochemical cork-graphite sensor was prepared to identify/quantify HCQ in river water matrices by differential pulse voltammetric (DPV) method. Subsequently, an HCQ-polluted river water sample was electrochemically treated with BDD electrode by applying 15, 30 and 45 mA cm−2. The HCQ decay and organic matter removal was monitored by DPV with composite sensor and chemical oxygen demand (COD) measurements, respectively. Results clearly confirmed that, on the one hand, the cork-graphite sensor exhibited good current response to quantify of HCQ in the river water matrix, with limit of detection and quantification of 1.46 mg L−1 (≈3.36 µM) and 4.42 mg L−1 (≈10.19 µM), respectively. On the other hand, the electrochemical oxidation (EO) efficiently removed HCQ from real river water sample using BDD electrodes. Complete HCQ removal was achieved at all applied current densities; whereas in terms of COD, significant removals (68%, 71% and 84% at 15, 30 and 45 mA cm−2, respectively) were achieved. Based on the achieved results, the offline integration of electrochemical SDG6 technologies in order to monitor and remove HCQ is an efficient and effective strategy.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app12020699

References

2020 - A rapid advice guideline for the diagnosis and treatment of 2019 novel coronavirus (2019-nCoV) infected pneumonia (standard version)
2021 - Candidate antiviral drugs for COVID-19 and their environmental implications: A comprehensive analysis [Crossref]
2020 - A systematic review and meta-analysis on chloroquine and hydroxychloroquine as monotherapy or combined with azithromycin in COVID-19 treatment [Crossref]
2020 - COVID-19 in Italy: Considerations on official data [Crossref]
2020 - How socio-economic and atmospheric variables impact COVID-19 and influenza outbreaks in tropical and subtropical regions of Brazil [Crossref]
2002 - Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: A review of recent research data [Crossref]
2014 - Reducing the Discharge of Micropollutants in the Aquatic Environment: The Benefits of Upgrading Wastewater Treatment Plants [Crossref]
2018 - Removal of organic micropollutants in waste stabilisation ponds: A review [Crossref]
2021 - Toxicity reduction of persistent pollutants through the photo-fenton process and radiation/H2O2 using different sources of radiation and neutral pH [Crossref]
2013 - Pharmaceuticals as emerging contaminants and their removal from water. A review [Crossref]