Heterogeneous electrocatalytic degradation of ciprofloxacin by ternary Ce3ZrFe4O14-x/CF composite cathode

Fluoroquinolone ciprofloxacin removal from synthetic and real wastewaters by single and combined electrochemical advanced oxidation processes. A review

Ciprofloxacin (CIP) is a widely prescribed fluoroquinolone antibiotic detected in the aquatic environment fostering the emergence of bacteria and posing risks the human health and ecosystem integrity. The present comprehensive critical review deals with CIP removal from synthetic and real wastewater by electrochemical advanced oxidation processes (EAOPs) up to 2024. Lower performance was obtained in real wastewaters than synthetic ones because their components scavenged-generated oxidizing agents. Anodic oxidation (AO) has been developed with active dimensionally stable anodes (DSA) and the non-active potent boron-doped diamond (BDD) one, where CIP solutions in chloride medium reached a maximal of 75 % mineralization. A more rapid CIP degradation and up to 96 % mineralization have been found for homogeneous electro-Fenton (EF) with Pt and Fe2+ catalyst. Heterogeneous Fenton with functionalized iron cathodes and solid iron catalysts, and heterogeneous EF-like with non-ferrous catalysts gave worse results. Novel modified EF processes with dual cathodes for direct.•OH production after H2O2 electrogeneration allowed up to 96 % mineralization. Photoelectro-Fenton (PEF) with UVA light and solar PEF (SPEF) can yield overall mineralization by the rapid photolysis of final Fe(III)-carboxylate species formed. Photoelectrocatalysis (PEC) with new photoanodes like FTO/Ni-ZnO under UVA light yielded 87 % mineralization. Hybrid AO, EF, PEF, and PEC processes with persulfate, O3, ultrasounds, or photocatalysis were more powerful than their single EAOPs. The characteristics and performance of each method, the generation of oxidants (•OH, O2•-, and/or 1O2), its reusability, and the by-products produced are discussed. The loss of toxicity of the treated solutions by EAOPs is finally detailed.

Synergy of oxygen reduction for H2O2 production and electro-fenton induced by atomic hydrogen over a bifunctional cathode towards water purification

In the Electro-Fenton (EF) process, hydrogen peroxide (H2O2) is produced in situ by a two-electron oxygen reduction reaction (2e ORR), which is further activated by electrocatalysts to generate reactive oxygen specieces (ROS). However, the selectivity of 2e transfer from catalysts to O2 is still unsatisfactory, resulting in the insufficient H2O2 availability. Carbon based materials with abundant oxygen-containing functional groups have been used as excellent 2e ORR electrocatalysts, and atomic hydrogen (H*) can quickly transfer one electron to H2O2 in a wide pH range and avoiding the restrict of traditional Fenton reaction. Herein, nickel nanoparticles growth on oxidized carbon deposited on modified carbon felt (Ni/Co@CFAO) was prepared as a bifunctional catalytic electrode coupling 2e ORR to form H2O2 with H* reducing H2O2 to produce ROS for highly efficient degradation of antibiotics. Electrochemical oxidation and thermal treatment were used to modulate the structure of carbon substrates for increasing the electro-generation of H2O2, while H* was produced over Ni sites through H2O/H+ reduction constructing an in-situ EF system. The experimental results indicated that 2e ORR and H* induced EF processes could promote each other mutually. The optimized Ni/Co@CFAO with a Ni:C mass ratio of 1:9 exhibited a high 2e selectivity and H2O2 yield of 49 mg L-1. As a result, the designed Ni/Co@CFAO exhibited excellent electrocatalytic ability to degrade tetracycline (TC) under different aqueous environmental conditions, and achieved 98.5% TC removal efficiency within 60 min H2O2 and H* were generated simultaneously at the bifunctional cathode and react to form strong oxidizing free radicals •OH. At the same time, O2 gained an electron to form •O2-, which could react with •OH and H2O to form 1O2, which had relatively long life (10-6∼10-3 s), further promoting the efficient removal of antibiotics in water.

Amino-functionalized graphene oxide affects bacteria-phage interactions in aquatic environments

The widespread use of graphene family nanomaterials (GFNs) in mass production has resulted in their release into the atmosphere, soil and water environment through various processes. Among these, the water environment is particularly affected by GFN pollution. Our previous study has demonstrated the impact of graphene oxide (GO) on bacteria-phage interactions in natural systems. However, the effects of amino-functionalized GO with a positive charge on bacteria-phage interactions in aquatic environments remain unclear. In the present study, we found that amino-functionalized graphene oxide (AGO) (0.05 mg/mL) inhibited the growth of Pseudomonas aeruginosa Y12. Furthermore, treating P. aeruginosa Y12 and phage with AGO (0.05 mg/mL) led to a reduced ratio of phage to bacteria, indicating that AGO can inhibit phage infection of bacteria. Additionally, the acidic environment exacerbated this effect by promoting electrostatic adsorption between the positively charged AGO and the negatively charged phage. Finally, a field water body intervention experiment showed that the richness and diversity of bacterial communities in six water samples changed due to AGO exposure, as revealed by Illumina analysis based on the bacterial 16S rRNA gene. These findings offer valuable insights into the environmental impacts of GFNs.

Environmental Application of Graphene and Its Forms for Wastewater Treatment: a Sustainable Solution Toward Improved Public Health

Public health is seriously jeopardized in developing countries due to poor sanitation and the presence of persistent pollutants in natural water bodies. Open dumping, wastewater discharge without proper treatment and atmospheric fallout of the organic and inorganic pollutants are the main causes behind the poor condition. Some of the pollutants pose a greater risk due to their toxicity and persistence. Such a class of pollutants are known as chemical contaminants of emerging concern (CECC), including antibiotics and drug residues, endocrine disruptors, pesticides and micro- and nano-plastics. Conventional treatment methods cannot treat them properly and are often associated with several disadvantages. However, the chronological development of techniques and materials for their treatment has exhibited graphene as an efficient candidate for environmental remediation. This current review considers the various graphene-based materials, their properties, advancement in synthesis methods with time and their detailed application in removing dyes, antibiotics and heavy metals. It has been discussed how graphene and its derivatives exhibit unique electronic, mechanical, structural and thermal properties. In this paper, the mechanism of adsorption and degradation using these graphene-based materials has also been discussed vividly. In addition to this, a bibliographic analysis was performed to identify the trend of research related to graphene and its derivatives in the adsorption and degradation of pollutants round the globe reflected by the publications. Therefore, this review can be instrumental in understanding the fact that further development of graphene-based materials and their mass production can provide a very effective and economical wastewater treatment method.

Comprehensive understanding of electrochemical treatment systems combined with biological processes for wastewater remediation

The presence of toxic pollutants in wastewater discharge can affect the environment negatively due to presence of the organic and inorganic contaminants. The application of the electrochemical process in wastewater treatment is promising, specifically in treating these harmful pollutants from the aquatic environment. This review focused on recent applications of the electrochemical process for the remediation of such harmful pollutants from aquatic environments. Furthermore, the process conditions that affect the electrochemical process performance are evaluated, and the appropriate treatment processes are suggested according to the presence of organic and inorganic contaminants. Electrocoagulation, electrooxidation, and electro-Fenton applications in wastewater have shown effective performance with high removal rates. The disadvantages of these processes are the formation of toxic intermediate metabolites, high energy consumption, and sludge generation. To overcome such disadvantages combined ecotechnologies can be applied in large-scale wastewater pollutants removal. The combination of electrochemical and biological treatment has gained importance, increased removal performance remarkably, and decreased operational costs. The critical discussion with depth information in this review could be beneficial for wastewater treatment plant operators throughout the world.

Recent advances in application of heterogeneous electro-Fenton catalysts for degrading organic contaminants in water

Over the last decades, advanced oxidation processes (AOPs) have been widely used in surface and ground water pollution control. The heterogeneous electro-Fenton (EF) process has gained much attention due to its properties of high catalytic performance, no generation of iron sludge, and good recyclability of catalyst. As of October 2022, the cited papers and publications of EF are around 1.3 × 10^-5 and 3.4 × 10^-3 in web of science. Among the AOP techniques, the contaminant removal efficiencies by EF process are above 90% in most studies. Current reviews mainly focused on the mechanism of EF and few reviews comprehensively summarized heterogeneous catalysts and their applications in wastewater treatment. Thus, this review focuses on the current studies covering the period 2012-2022, and applications of heterogeneous catalysts in EF process. Two kinds of typical heterogeneous EF systems (the addition of solid catalysts and the functionalized cathode catalysts) and their applications for organic contaminants degradation in water are reviewed. In detail, solid catalysts, including iron minerals, iron oxide-based composites, and iron-free catalysts, are systematically described. Different functionalized cathode materials, containing Fe-based cathodes, carbonaceous-based cathodes, and heteroatom-doped cathodes, are also reviewed. Finally, emphasis and outlook are made on the future prospects and challenges of heterogeneous EF catalyst for wastewater treatments.

Progress of homogeneous and heterogeneous electro-Fenton treatments of antibiotics in synthetic and real wastewaters. A critical review on the period 2017-2021

Antibiotics are widely supplied over all the world to animals and humans to fight and heal bacteriological diseases. The uptake of antibiotics has largely increased the average-life expectancy of living beings. However, these recalcitrant products have been detected at low concentrations in natural waters, with potential health risks due to alterations in food chains and an increase in the resistance to bacterial infection, control of infectious diseases, and damage of the beneficial bacteria. The high stability of antibiotics at mild conditions prevents their effective removal in conventional wastewater treatment plants. A powerful advanced oxidation processes such as the electro-Fenton (EF) process is being developed as a guarantee for their destruction by ^•OH generated as strong oxidant. This review presents a critical, exhaustive, and detailed analysis on the application of EF to remediate synthetic and real wastewaters contaminated with common antibiotics, covering the period 2017-2021. Homogeneous EF and heterogeneous EF involving iron solid catalysts or iron functionalized cathodes, as well as their hybrid and sequential treatments, are exhaustively examined. Their fundamentals and characteristics are detailed, and the main results obtained for the removal of the most used antibiotic families are carefully described and discussed. The role of generated oxidizing agents is explained, and the by-products generated, and reaction sequences proposed are detailed.

Characteristics and mechanisms of ciprofloxacin degradation by black soldier fly larvae combined with associated intestinal microorganisms

Antibiotics are challenging to degrade and are excreted by livestock which results in environmental pollution. In this paper, we demonstrated that environmentally friendly manure bioremediation performed by black soldier fly larvae (BSFL) is a wise alternative, which could effectively degrade ciprofloxacin (CIP) by approached 85.48% in artificial diet and 84.22% in poultry manure within 12 days. They are up to 2.5-4.0 fold more than that achieved by natural fermentation. The five CIP-degrading strains were isolated from the larval gut, two of which, named by Klebsiella pneumoniae BSFLG-CIP1 and Proteus mirabilis BSFLG-CIP5, could degraded CIP by nearly 98.22% and 97.83% in vitro, respectively. When the intestinal isolates were re-inoculated to sterile BSFL system, the degradation level significantly increased up to 82.38%, comparing with the sterile BSFL system (21.76%). It is proved that the larvae intestinal microbiota might carry out this highly-efficient CIP-degradation. Furthermore, seven possible metabolites were identified for CIP-degradation in vitro, and they were referring three main potential degrading mechanisms of hydroxylize, piperazine ring substitute and cleavage, and quinoline ring cleavage. In conclusion, the present study may provide a strategy to reduce antibiotics pollution in animal waste through bioremediation with BSFL and adjusted intestinal microbes.

Electrocatalytic oxidation of ciprofloxacin by Co-Ce-Zr/γ-Al2O3 three-dimensional particle electrode

In this work, Co-Ce-Zr/γ-Al₂O3₃ particle electrodes were prepared for the efficient degradation of ciprofloxacin (CIP). Co-Ce-Zr/γ-Al₂O₃ particle electrodes were analyzed with a scanning electron microscope (SEM), X-Ray Diffraction (XRD), X-Ray Fluorescence Spectrometer (XRF), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). According to the results, significant amounts of Co₃O₄, CeO₂, and ZrO₂ were formed on the Co-Ce-Zr/γ-Al₂O₃ particle electrodes. It was shown that when the conditions of the reaction system were at pH=6, conductivity of 4 ms/cm, current of 0.2 A, initial pollutant concentration of 100 mg/L, and material dosage of 15 g, CIP could be completely degraded within 40 min, and the energy consumed in the reaction was 41.3 kWh/kg CIP. The rate of total organic carbon (TOC) removal by Co-Ce-Zr/γ-Al₂O₃ particle electrodes was recorded to be approximately 52.6%. Using a response surface methodology, we explored the optimal operating conditions. At the same time, we also explored the influence of inorganic anions in water and actual water medium on the rate of CIP removal. In addition, the ESR data proved that the main active substance in the reaction system was ·OH. The degradation intermediates were investigated, and the possible mechanism was proposed. Thus, this research provided a new solution for the treatment of antibiotic-containing wastewater.

Highly Efficient Degradation of Polyacrylamide by an Fe-Doped Ce0.75Zr0.25O2 Solid Solution/CF Composite Cathode in a Heterogeneous Electro-Fenton Process

Polyacrylamide (PAM) in environmental water has become a major problem in water pollution management due to its high molecular mass, corrosion resistance, high viscosity, and nonabsorption by soil. The composite of Fe-doped Ce_0.75Zr_0.25O₂ solid solution (Fe-Ce_0.75Zr_0.25O₂) loaded on carbon felt (CF) was fabricated by a hydrothermal synthesis method, which was used as the cathode in a heterogeneous electro-Fenton system for the degradation of PAM. It showed that the degradation efficiency of PAM by the Fe-Ce_0.75Zr_0.25O₂/CF cathode was 86% after 120 min and the molecular mass of PAM decreased by more than 90% after 300 min. Total organic carbon removal reached 78.86% in the presence of Fe-Ce_0.75Zr_0.25O₂/CF, while the value was only 38.01% in the absence of Fe-Ce_0.75Zr_0.25O₂. Further studies showed that the breaking of the chain begins with the amide bond, and then, the carbon chain was cracked into a short alkyl chain. As degradation progressed, both the complex viscosity and elasticity modulus of PAM solutions decreased nearly 50% at 300 min. It indicated that ^•OH were the most significant active species for the degradation of PAM. This novel Fe-Ce_0.75Zr_0.25O₂/CF composite is an efficient and promising electrode for the removal of PAM in wastewater.