Effective removal of the antibiotic Nafcillin from water by combining the Photoelectro-Fenton process and Anaerobic Biological Digestion
Graphical abstract
Introduction
Antibiotics are chemicals that contain active ingredients, designed to treat bacterial infections in humans, but also used in veterinary medicine for therapeutic, prophylactic and growth promotion purposes (Katzung et al., 2013). However, in spite of their usefulness, a great amount and variety of antibiotics are discharged into natural sources through wastewater carrying human excreta; by improper disposal of medications thrown into the toilet; and by liquid agricultural residues, including livestock manure (Kim et al., 2013). These actions generate a great deal of concern about the emergence of bacterial resistance and its consequences for human health, and about the toxic effects on aquatic ecosystems (Serna-Galvis et al., 2015, Serna-Galvis et al., 2016a, Serna-Galvis et al., 2016b).
β-lactams are among the antibiotics frequently detected in hospital wastewater and livestock, and one of them is Nafcillin (NAF) (Kummerer, 2009). NAF belongs to the penicillin family, and has a broad spectrum and intrinsic antibacterial activity. Furthermore, NAF is used in infections caused by Gram (+) germs, such as hemolytic and non-hemolytic streptococci, S. pneumoniae, non-β-lactamase staphylococci, Clostridia spp., B. anthracis, Listeria monocytogenes and most strains of enterococci (Kemper, 2008).
Currently, β-lactam antibiotics are very difficult to remove by means of conventional biological processes. Due to their low biodegradability, they can cause adverse effects on the strains of microorganisms used in wastewater treatment plants. In addition, these antibiotics are also photoresistent and escapes conventional physical treatments such as coagulation (Giraldo-Aguirre et al., 2015, Sirés and Brillas, 2016).
For all the reasons above, the use of non-conventional technologies such as electrochemical advanced oxidation processes (EAOPs) becomes necessary, as it allows the degradation of recalcitrant organic compounds like antibiotics into CO2 or products that could be more biodegradable, facilitating the exchange with biological systems.
EAOPs are based on the in-situ generation of the hydroxyl radical, the most powerful radical oxidant (with a standard potential of 2.80 V/SHE), which can react non-selectively with most organics up to their mineralization to CO2, water and inorganic ions (García-Segura et al., 2013, García-Rodríguez et al., 2016, Benito et al., 2017).
EAOPs based on Fenton's reaction chemistry such as electro-Fenton and photoelectro-Fenton processes have been widely used in the treatment of wastewater containing persistent and emergent organic pollutants (Brillas et al., 2009, Brillas and Martínez-Huitle, 2015). In these Fenton-based processes, the Fe2 + ion is added to the water solution as a catalyst that reacts with H2O2, producing •OH from Fenton's reaction with an optimum pH 2.8, as shown by Eq. (1) (Olvera-Vargas et al., 2015, Pereira et al., 2016).
H2O2 used in the Fenton reaction is electrogenerated on the cathode in-situ by injecting oxygen or air (Eq. (2)), for example, at a carbon-PTFE gas (O2 or air) diffusion cathode (Salazar et al., 2011).
Eq. (1) is catalytic and can be mainly propagated from the Fe3 + reduction to Fe2 + at the cathode.
When an undivided cell is used in EF, organics can also be attacked by heterogeneous •OH formed on the anode surface showed in Eq. (3) (Espinoza et al., 2016, Trellu et al., 2016). Organic compounds can achieve a total mineralization in an aqueous medium by the action of physisorbed M(•OH) formed during the electrolysis of water to O2, a method that is called electro-oxidation process (EO) (Salazar et al., 2016, Pérez et al., 2017, Raschitor et al., 2017). Currently, the preferred anode for EO-H2O2 is the Boron-doped diamond (BDD) thin-film electrode, which have: i) an inert surface, ii) low adsorption properties, iii) remarkable corrosion stability and iv) a high O2-overvoltage in aqueous medium, which results in the production of reactive BDD(•OH), as shown by Eq. (3). (García-Segura et al., 2015, Martínez-Huitle et al., 2015).
In PEF, the degradation rate of organic pollutants is enhanced under the simultaneous irradiation of the solution with UV light due to: (i) the greater Fe2 + regeneration and •OH production by photolysis of Fe(OH)2 + (the pre-eminent Fe3 + species in solution at pH near 3), as shown in Eq. (4); and (ii) the photodecarboxylation of complexes of Fe(III) with generated carboxylic acids, which are attacked by •OH, Eq. (5) (El-Ghenymy et al., 2015, Vidal et al., 2016, García-Segura et al., 2017).
During the last time, EAOPs have been combined with biological treatments to remove contaminants that are not biologically eliminated (Moreira et al., 2015). In aerobic digestion, a group of microorganisms (mainly bacteria and protozoa) act in the presence of oxygen on both the dissolved organic matter and the dissolved, colloidal and suspended inorganic matter found in wastewater, transforming them into gases and cellular matter that can be easily separated by sedimentation (Eq. (6)) (Chiavola et al., 2014, Zhou et al., 2017). The union of organic matter, bacteria and mineral substances forms flocs and set, it knows as biological sludge (Inyang et al., 2016).
On the other hand, one process less studied but very attractive at the energy level is anaerobic digestion. Anaerobic digestion produces the decomposition of organic matter in the absence of molecular oxygen. In this process organic matter is biologically converted, into methane (CH4) and carbon dioxide (CO2) (Eq. (7)); CH4 could be used as fuel future (Amaral et al., 2014, Ikumi et al., 2014, Vidal et al., 2016). The anaerobic degradation requires the intervention of several groups of facultative microorganisms, which use the metabolic products generated in each stage in a sequential way. This process involves three large trophic groups and four stages of transformation: hydrolysis: bacteria hydrolyze the organic compounds in simpler monomers; acidogenesis, fermentative bacteria produce the conversion of the monomers into short chain volatile fatty acids; acetogenesis: acetogenic bacteria convert short chain volatile fatty acids into acetic acid, carbon dioxide and hydrogen and methanogenesis; methanogenic archaea produce methane gas (Montalvo and Lorna, 2003).
In this work, the degradation of the antibiotic Nafcillin by means of the combination of coupled treatments was studied. As a primary treatment, three electrochemical advanced oxidation processes (electro-oxidation in the presence of hydrogen peroxide ((EO-H2O2), EF and SPEF) were applied to find the best process to degrade and mineralize NAF. After the application of each treatment, the antimicrobial activity of the electrolyzed solutions was evaluated. Finally, anaerobic digestion was applied to reach the complete mineralization of the solutions.
Section snippets
Reagents
Sodium Nafcillin (CAS number: 985-16-0, C21H22N2NaO5S, 99.9% of purity) supplied by Sigma-Aldrich® was used as received. The chemical structure as well as some characteristics of NAF are shown in Table 1. Analytical grade oxamic and malic acids were from Sigma-Aldrich®, while oxalic, maleic, formic and acetic were from Merck®. Solutions of anhydrous sodium sulfate, used as supporting electrolyte, and iron sulfate II heptahydrate are analytical grade from Merck. All solutions were prepared with
Electrochemical degradation of NAF
EO-H2O2, EF, PEF and a photolysis processes were applied to degrade NAF in order to find the most effective before treating NAF solutions with a biologic process. These experiments were performed using a concentration of 50 mg L− 1 in 0.05 M Na2SO4 with 1 mg L− 1 Fe2 + (for EF and PEF experiments) in 0.250 L solution at pH 2.8. The change in the concentration of NAF was followed by reversed-phase UHPLC, where concentration displayed a well-defined peak at 6.7 min of rt. Fig. 1A shows the change in the
Conclusions
It was determined that the antibiotic NAF can be degraded and partially mineralized by PEF using a BDD anode, air diffusion cathode, and exposure to UV radiation. Complete degradation and elimination of antimicrobial activity in an aqueous antibiotic solution after 90 min of electrolysis was achieved by applying a current density of 2 mA cm− 2 in the presence of 1.0 mg L− 1 concentration of Fe2 + in an electrolytic medium of Na2SO4 0.05 M at pH 2.8. PEF allows greater decay of the antibiotic
Acknowledgements
The authors thank the financial support of FONDECYT Grant 1170352, DICYT-USACH, CONICYT FONDEQUIP/UHPLC-MS/MS EQM 120065 and to COLCIENCIAS project “Desarrollo y evaluación de un sistema electroquímico asistido con luz solar para la eliminación de contaminantes emergentes en agua (No. 111565842980 Convocatoria 658, 2014). J. Vidal thanks CONICYT for the National PhD scholarship 21140248 and Pacific Alliance Scholarship. Finally, we are grateful to “Proyectos Basales y Vicerrectoría de
References (46)
- et al.
Electrochemical mineralization of the azo dye Acid Red 29 (Chromotrope 2R) by photoelectro – Fenton process
Chemosphere
(2012) - et al.
Color, organic matter and sulfate removal from textile effluents by anaerobic and aerobic processes
Bioresour. Technol.
(2014) - et al.
Degradation pathways of aniline in aqueous solutions during electro-oxidation with BDD electrodes and UV/H2O2 treatment
Chemosphere
(2017) - et al.
Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review
Appl. Catal. B Environ.
(2015) - et al.
Biological treatment of olive mill wastewater in a sequencing batch reactor
Biochem. Eng. J.
(2014) - et al.
Mineralization of sulfanilamide by electro-Fenton and solar photoelectro-Fenton in a pre-pilot plant with a Pt/air-diffusion cell
Chemosphere
(2013) - et al.
Comparative use of anodic oxidation, electro-Fenton and photoelectro-Fenton with Pt or boron-doped diamond anode to decolorize and mineralize Malachite Green oxalate dye
Electrochim. Acta
(2015) - et al.
Mineralization of the textile dye acid yellow 42 by solar photoelectro-Fenton in a lab-pilot plant
J. Hazard. Mater.
(2016) - et al.
Use of a carbon felt–iron oxide air-diffusion cathode for the mineralization of Malachite Green dye by heterogeneous electro-Fenton and UVA photoelectro-Fenton processes
J. Electroanal. Chem.
(2016) - et al.
Mineralization of phthalic acid by solar photoelectro-Fenton with a stirred boron-doped diamond/air-diffusion tank reactor: influence of Fe3 + and Cu2 + catalysts and identification of oxidation products
Electrochim. Acta
(2013)
Role of sp3/sp2 ratio on the electrocatalytic properties of boron-doped diamond electrodes: a mini review
Electrochem. Commun.
Effect of the Fe3 +/Cu2 + ratio on the removal of the recalcitrant oxalic and oxamic acids by electro-Fenton and solar photoelectro-Fenton
Sol. Energy
Enhancement of biodegradability of o-toluidine effluents by electro-assisted photo-Fenton treatment
Process Saf. Environ. Prot.
Biotransformation of trace organic compounds by activated sludge from a biological nutrient removal treatment system
Bioresour. Technol.
Veterinary antibiotics in the aquatic and terrestrial environment
Ecol. Indic.
Degradation of veterinary antibiotics by dielectric barrier discharge plasma
Chem. Eng. J.
The presence of pharmaceuticals in the environment due to human use-present knowledge and future challenges
J. Environ. Manag.
Remediation of a winery wastewater combining aerobic biological oxidation and electrochemical advanced oxidation processes
Water Res.
Electro-Fenton and solar photoelectro-Fenton treatments of the pharmaceutical ranitidine in pre-pilot flow plant scale
Sep. Purif. Technol.
Effective removal of Orange-G azo dye from water by electro-Fenton and photoelectro-Fenton processes using a boron-doped diamond anode
Sep. Purif. Technol.
Treatment of real effluents from the pharmaceutical industry: a comparison between Fenton oxidation and conductive-diamond electro-oxidation
J. Environ. Manag.
Application of electrochemical advanced oxidation processes to the mineralization of the herbicide diuron
Chemosphere
Mineralization of acid yellow 36 azo dye by electro-Fenton and solar photoelectro-Fenton processes with a boron-doped diamond anode
Chemosphere
Cited by (45)
A coupling mechanism of anodic oxygen evolution reaction during organic pollutants oxidation
2023, Journal of Electroanalytical ChemistryDegradation of antibiotics by electrochemical advanced oxidation processes (EAOPs): Performance, mechanisms, and perspectives
2023, Science of the Total Environment