A combined advanced oxidation process: Electrooxidation-ozonation for antibiotic ciprofloxacin removal from aqueous solution

Antibiotic ciprofloxacin removal from aqueous solutions by electrochemically activated persulfate process: Optimization, degradation pathways, and toxicology assessment

Ciprofloxacin (CIP) is a commonly used antibiotic in the fluoroquinolone group and is widely used in medical and veterinary medicine disciplines to treat bacterial infections. When CIP is discharged into the sewage system, it cannot be removed by a conventional wastewater treatment plant because of its recalcitrant characteristics. In this study, boron-doped diamond anode and persulfate were used to degrade CIP in an aquatic solution by creating an electrochemically activated persulfate (EAP) process. Iron was added to the system as a coactivator and the process was called EAP+Fe. The effects of independent variables, including pH, Fe2+, persulfate concentration, and electrolysis time on the system were optimized using the response surface methodology. The results showed that the EAP+Fe process removed 94% of CIP under the following optimum conditions: A pH of 3, persulfate/Fe2+ concentration of 0.4 mmol/L, initial CIP concentration 30 mg/L, and electrolysis time of 12.64 min. CIP removal efficiency was increased from 65.10% to 94.35% by adding Fe2+ as a transition metal. CIP degradation products, 7 pathways, and 78 intermediates of CIP were studied, and three of those intermediates (m/z 298, 498, and 505) were reported. The toxicological analysis based on toxicity estimation software results indicated that some degradation products of CIP were toxic to targeted animals, including fathead minnow, Daphnia magna, Tetrahymena pyriformis, and rats. The optimum operation costs were similar in EAP and EAP+Fe processes, approximately 0.54 €/m3.

Comparative study on electro-regeneration of antibiotic-laden activated carbons in reverse osmosis concentrate

Electro-regeneration is emerging as a new technique to regenerate spent carbon adsorbents through an electrochemical process. In this study, sequential adsorption and electro-regeneration of ciprofloxacin (CIP)-laden carbon were investigated using both pristine and iron (Fe)-doped F400 activated carbon in distilled, deionized (DI) water and reverse osmosis (RO) concentrate water. The impact of reactor flow rate and sequential adsorption/electro-regeneration cycles on the regeneration efficiency were also evaluated. The results indicate that the breakthrough points for both adsorbents in DI water, where 100 % of the CIP molecules were adsorbed, occurred at around 7,800 bed volumes (BVs). Conversely, electro-regeneration for both adsorbents, where 94 % of the CIP molecules were desorbed, took place at 380 BVs. The main distinction between the two activated carbons lies in the initial range of BVs (<400 BVs).Fe doping on F400 appears to enhance its surface selectivity for CIP uptake, which can easily diffuse into the meso/macropore regions of Fe-doped F400. In contrast, pristine F400, being highly microporous, necessitated more contact time to fill its high-energy sites, resulting in a higher affinity for CIP adsorption. Over the four sequential adsorption/electro-regeneration cycles in DI water, a similar regeneration efficiency was observed at 190 BVs. As the flow rate increased from 2 to 6 mL/min, the CIP uptake on pristine F400 decreased in DI water, calculating 138, 74 and 57 mg/g for flow rates of 2, 4, and 6 mL/min, respectively. When the RO concentrate water was compared with DI water, the pristine F400 quickly reached saturation due to pore blockage caused by organic matter in RO concentrate. During electro-regeneration, up to 100 % of adsorbed CIP molecules were desorbed at around 120 BVs in RO concentrate, which is 3X faster than DI water. The effectiveness of this technology can be enhanced by implementing continuous flow systems, thereby improving the overall efficiency of CIP removal in RO concentrate.

Advances on electrochemical disinfection research: Mechanisms, influencing factors and applications

Disinfection, a vital barrier against pathogenic microorganisms, is crucial in halting the spread of waterborne diseases. Electrochemical methods have been extensively researched and implemented for the inactivation of pathogenic microorganisms from water and wastewater, primarily owing to their simplicity, efficiency, and eco-friendliness. This review succinctly outlined the core mechanisms of electrochemical disinfection (ED) and systematically examined the factors influencing its efficacy, including anode materials, system conditions, and target species. Additionally, the practical application of ED in water and wastewater treatment was comprehensively reviewed. Case studies involving various scenarios such as drinking water, hospital wastewater, black water, rainwater, and ballast water provided concrete instances of the expansive utility of ED. Finally, coupling ED with other technologies and the resulting synergies were introduced as pivotal foundations for subsequent engineering advancements.

Synergetic effects of catalyst-surface dual-electric centers and microbes for efficient removal of ciprofloxacin in water

Antibiotics and antibiotic resistance genes (ARGs) are still a problem in biological treatment. Herein, we propose a synergetic strategy between microbes and dual-electric centers catalysts (CCN/Cu-Al2O3/ceramsite) for Ciprofloxacin (CIP)-contained (5 mg/L) water treatment in an up-flow biological filter. CIP was cleaved into small molecules by the catalyst, bringing a 57.6% removal and reducing 10.5% ARG. The characterization results verified that a Cu-π electrostatic force occurs on the catalyst surface, forming electron-rich areas around Cu and electron-poor areas at the carbon-doped g-C3N4 (CCN) aromatic ring. Thus, the electrons of adsorbed CIP were delocalized and then captured by the adsorbed extracellular polymeric substance at the electron-rich areas. Therefore, the synergetic process weakened the stress of CIP on bacteria and reduced ARG accumulation. It also enriched more electro-active bacteria on the surface of CCN/Cu-Al2O3/ceramsite, promoting the expression of extracellular electron transfer-related genes and reconstructing the energy metabolism mode. This result provides an opportunity for refractory antibiotic treatment in the biological process.

Electrochemical-based processes for produced water and oily wastewater treatment: A review

The greatest volume of by-products produced in oil and gas recovery operations is referred to as produced water and increasing environmental concerns and strict legislations on discharging it into the environment cause to more attention for focusing on degradation methods for treatment of produced water especially electrochemical technologies. This article provides an overview of electrochemical technologies for treating oily wastewater and produced water, including: electro-coagulation, electro-Fenton, electrochemical oxidation and electrochemical membrane reactor as a single stage and combination of these technologies as multi-stage treatment process. Many researchers have carried out experiments to examine the impact of various factors such as material (i.e, electrode material) and operational conditions (i.e., potential, current density, pH, electrode distance, and other factors) for organic elimination to obtain the high efficiency. Results of each method are reviewed and discussed according to these studies, comprehensively. Furthermore, several challenges need to be overcome and perspectives for future study are proposed for each 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.

Degradation of antibiotics by electrochemical advanced oxidation processes (EAOPs): Performance, mechanisms, and perspectives

Global consumption and discharge of antibiotics have led to the rapid development and spread of bacterial antibiotic resistance. Among treatment strategies, electrochemical advanced oxidation processes (EAOPs) are gaining popularity for treating water/wastewater containing antibiotics due to their high efficiency and easiness of operation. In this review, we summarize various forms of EAOPs that contribute to antibiotic degradation, including common electrochemical oxidation (EO), electrolyte enhanced EO, electro-Fenton (EF) processes, EF-like process, and EAOPs coupling with other processes. Then we assess the performance of various EAOPs in antibiotic degradation and discuss the influence of key factors, including electrode, initial concentration and type of antibiotic, operation conditions, electrolyte, and water quality. We also review mechanisms and degradation pathways of various antibiotics degradation by EAOPs, and address the species and toxicity of intermediates produced during antibiotics treatment. Finally, we highlight challenges and critical research needs to facilitate the application of EAOPs in antibiotic treatment.

Effect of electrode parameters in the electro-production of reactive oxidizing species via boron-doped diamond under batch mode

Ozone and hydroxyl radicals (^• OH) are powerful reactive oxidizing species (ROS) that are commonly utilized in water disinfection. The electrochemical advanced oxidation process (EAOP) is often used to generate such oxidants, whereas optimizing its experimental setup and electrode parameters plays a crucial role in its performance. This research aims to find the optimal setup for ROS generation process from tap water via the boron-doped diamond. The effect of electrode's active area, type of electrode substrates (mesh or sheet), type of mesh substrate (rolled and unrolled), and number of anodes and cathodes are examined. The results showed that the use of two long-rolled BDD/Nb meshes as anode and one long-rolled mesh as a cathode gives the optimal performance of electrolysis process at 15 V potential and 3 min. These results will provide a start for developing a cost accepted, health-safe, household disinfection device that reduces susceptibility to human life-threatening waterborne diseases. PRACTITIONER POINTS: This research aims to find the optimal setup for ROS generation process from tap water via the boron-doped diamond. The effect of electrode's parameters on the electro-production of ROS is examined. The best performance is achieved using rolled mesh electrodes. Two long-rolled BDD/Nb meshes as anode electrodes and one long-rolled mesh cathode electrode give the optimal electrolysis process performance.

Low-cost Posidonia oceanica bio-adsorbent for efficient removal of antibiotic oxytetracycline from water

The presence of antibiotics as micro-contaminants in the water and aqueous environments is a health concern to humans and the ecosystem. Therefore, their elimination by adsorption to available and cheap materials in water treatment plants is a research topic of high relevance. The present paper reports on the adsorption behavior of oxytetracycline on a bio-adsorbent prepared from Posidonia oceanica; an abundant Mediterranean biomass. Characterization of the pretreated Posidonia biomaterial was achieved using several analyses such as Boehm acid-base titration method, pH_PZC determination, and analysis techniques (FTIR, ¹³C CP-MAS NMR, optical microscopy, and TGA). The pH_PZC occurred around pH 2.11. Posidonia biomaterial showed a fast and high uptake rate throughout the adsorption process, which is a definite advantage for analytical applications such as water decontamination. The experimental kinetic data fitted very rightly the pseudo-second-order kinetic model and the equilibrium uptake can adopt the bi-Langmuir isotherm model for all studied pH values which assumes adsorptions at the two localized sites. Maximum adsorption capacities of 11.8 mg∙g^-1 and 4.4 mg∙g^-1 for the two adsorption sites are reached at pH 6. The oxytetracycline adsorption process onto Posidonia bio-adsorbent is spontaneous (Δ_adsG⁰ < 0), exothermic (Δ_adsH⁰ < 0), and entropically favorable (Δ_adsS⁰ > 0). The effect of pH on adsorption behavior and the thermodynamic parameters of adsorption are consistent with a possible origin of adsorption of oxytetracycline by means of hydrogen bonding interactions between surface hydroxyl and phenolic groups of the biomaterial and oxytetracycline. The proposed green and environmentally friendly biomaterial offers potential benefits as a bio-adsorbent in the remediation of aquatic environments contaminated by various organic materials.

Electrochemical Degradation of Methylene Blue by a Flexible Graphite Electrode: Techno-Economic Evaluation

In this study, electrochemical removal of methylene blue (MB) from water using commercially available and low-cost flexible graphite was investigated. The operating conditions such as initial dye concentration, initial solution pH, electrolyte dose, electrical potential, and operating time were investigated. The Box-Behnken experimental design (BBD) was used to optimize the system's performance with the minimum number of tests possible, as well as to examine the independent variables' impact on the removal efficiency, energy consumption, operating cost, and effluent MB concentration. The electrical potential and electrolyte dosage both improved the MB removal efficiency, since increased electrical potential facilitated production of oxidizing agents and increase in electrolyte dosage translated into an increase in electrical current transfer. As expected, MB removal efficiency increased with longer operational periods. The combined effects of operating time-electrical potential and electrical potential-electrolyte concentration improved the MB removal efficiency. The maximum removal efficiency (99.9%) and lowest operating cost (0.012 $/m³) were obtained for initial pH 4, initial MB concentration 26.5 mg/L, electrolyte concentration 0.6 g/L, electrical potential 3 V, and operating time 30 min. The reaction kinetics was maximum for pH 5, and as the pH increased the reaction rates decreased. Consequent techno-economic assessment showed that electrochemical removal of MB using low-cost and versatile flexible graphite had a competitive advantage.

Antibiotics degradation by UV/chlor(am)ine advanced oxidation processes: A comprehensive review

Antibiotics are emerging contaminants in aquatic environments which pose serious risks to the ecological environment and human health. Advanced oxidation processes (AOPs) based on ultraviolet (UV) light have good application prospects for antibiotic degradation. As new and developing UV-AOPs, UV/chlorine and derived UV/chloramine processes have attracted increasing attention due to the production of highly reactive radicals (e.g., hydroxyl radical, reactive chlorine species, and reactive nitrogen species) and also because they can provide long-lasting disinfection. In this review, the main reaction pathways of radicals formed during the UV/chlor (am)ine process are proposed. The degradation efficiency, influencing factors, generation of disinfection by-products (DBPs), and changes in toxicity that occur during antibiotic degradation by UV/chlor (am)ine are reviewed. Based on the statistics and analysis of published results, the effects caused by energy consumption, defined as electrical energy per order (EE/O), increase in the following order: UV/chlorine < UV/peroxydisulfate (PDS)< UV/H₂O₂ < UV/persulfate (PS) < 265 nm and 285 nm UV-LED/chlorine (EE/O). Some inherent problems that affect the UV/chlor (am)ine processes and prospects for future research are proposed. The use of UV/chlor (am)ine AOPs is a rich field of research and has promising future applications, and this review provides a theoretical basis for that.

Efficient removal of antibiotics from water resources is a public health priority: a critical assessment of the efficacy of some remediation strategies for antibiotics in water

This review discusses the fundamental principles and mechanism of antibiotic removal from water of some commonly applied treatment techniques including chlorination, ozonation, UV-irradiation, Fenton processes, photocatalysis, electrochemical-oxidation, plasma, biochar, anaerobicdigestion, activated carbon and nanomaterials. Some experimental shortfalls identified by researchers such as certain characteristics of degradation agent applied and the strategies explored to override the identified limitations are briefly discussed. Depending on interactions of a range of factors including the type of antibiotic compound, operational parameters applied such as pH, temperature and treatment time, among other factors, all reviewed techniques can eliminate or reduce the levels of antibiotic compounds in water to varying extents. Some of the reviewed techniques such as anaerobic digestion generally require longer treatment times (up to 360, 193 and 170 days, according to some studies), while others such as photocatalysis achieved degradation within short contact time (within a minimum of 30, but up to 60, 240, 300 and 1880 minutes, in some cases). For some treatment techniques such as ozonation and Fenton, it is apparent that subjecting compounds to longer treatment times may improve elimination efficiency, whereas for some other techniques such as nanotechnology, application of longer treatment time generally meant comparatively minimal elimination efficiency. Based on the findings of experimental studies summarized, it is apparent that operational parameters such as pH and treatment time, while critical, do not exert sole or primary influence on the elimination percentage(s) achieved. Elimination efficiency achieved rather seems to be due more to the force of a combination of several factors.

Electrochemical oxidation of ciprofloxacin in different aqueous matrices using synthesized boron-doped micro and nano-diamond anodes

The present work investigates the electrocatalytic performance of two different morphologies of boron doped-diamond film electrode (microcrystalline diamond - MCD, and nanocrystalline diamond - NCD) used in electrochemical oxidation for the removal of the antibiotic ciprofloxacin (CIP). A thorough study was conducted regarding the formation of the MCD and NCD films through the adjustment of methane in CH₄/H₂ gas mixture, and the two films were compared in terms of crystalline structure, apparent doping level, and electrochemical properties. The physicochemical results showed that the NCD film had higher sp² carbon content and greater doping level; this contributed to improvements in its surface roughness, as well as its specific capacitance and charge transfer, which consequently enhanced its electrocatalytic activity in comparison with the MCD. The results obtained from CIP removal and mineralization assays performed in sulfate medium also showed that the NCD was more efficient than the MCD under all the current densities investigated. The effects of CIP concentration and the evolution of the final by-products, including short-chain carboxylic acids and inorganic ions, were also investigated. The electrochemical performance of the NCD was evaluated in different aqueous matrices, including chloride medium, real wastewater and simulated urine. The application of the NCD led to complete or almost complete CIP degradation, regardless of the medium employed. The kinetic constant rates obtained under the different media investigated were as follows: synthetic urine (0.0416 min^-1 - R² = 0.991) < real wastewater (0.0923 min^-1 R² = 0.997) < synthetic matrix containing chloride (0.1992 min^-1 - R² = 0.995); this shows that the pollutant degradation was affected by the type of aqueous matrix and the oxidants that were electrogenerated in situ. The results obtained from the analysis of electrical energy per order (EE/O) showed that the treatment of simulated urine spkiked with required the highest energy consumption, followed by the real effluent and synthetic matrix containing chloride. The present study proves the viability of electrocatalytic nanostructured materials to the treatment of antibiotics in complex matrices.

Mesoporous and adsorption behavior of algal biochar prepared via sequential hydrothermal carbonization and ZnCl2 activation

In this study, biochar derived from brown algal Ascophyllum nodosum was synthesized through hydrothermal carbonization (HTC) coupling with ZnCl₂ chemical activation and applied as a sustainable adsorbent for antibiotic removal from water exemplified by ciprofloxacin (CIP). Various surface analysis techniques such as Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and zeta potential were used to clarify the surface properties of prepared biochars. The adsorption performance of biochars was investigated using batch adsorption experiments with a variety of parameters (initial pH, ionic types, temperature and water matrixes). The application of prepared biochar in CIP removal showed a good result of adsorption capacity (150-400 mg g^-1) in different conditions. Overall, algal biochars, as a product recycled from biowaste, demonstrated a novel and promising adsorbent for effective and sustainable method for removal of antibiotics from water.

Antibiotic-metal complexes in wastewaters: fate and treatment trajectory

Unregulated usage, improper disposal, and leakage from pharmaceutical use and manufacturing sites have led to high detection levels of antibiotic residues in wastewater and surface water. The existing water treatment technologies are insufficient for removing trace antibiotics and these residual antibiotics tend to interact with co-existing metal ions and form antibiotic-metal complexes (AMCs) with altered bioactivity profile and physicochemical properties. Typically, antibiotics, including tetracyclines, fluoroquinolones, and sulphonamides, interact with heavy metals such as Fe²⁺, Co²⁺, Cu²⁺, Ni²⁺, to form AMCs which are more persistent and toxic than parent compounds. Although many studies have reported antibiotics detection, determination, distribution and risks associated with their environmental persistence, very few investigations are published on understanding the chemistry of these complexes in the wastewater and sludge matrix. This review, therefore, summarizes the structural features of both antibiotics and metals that facilitate complexation in wastewater. Further, this work critically appraises the treatment methods employed for antibiotic removal, individually and combined with metals, highlights the knowledge gaps, and delineates future perspectives for their treatment.

Removal of Pharmaceuticals from Water by Adsorption and Advanced Oxidation Processes: State of the Art and Trends

Pharmaceutical products have become a necessary part of life. Several studies have demonstrated that indirect exposure of humans to pharmaceuticals through the water could cause negative effects. Raw sewage and wastewater effluents are the major sources of pharmaceuticals found in surface waters and drinking water. Therefore, it is important to consider and characterize the efficiency of pharmaceutical removal during wastewater and drinking-water treatment processes. Various treatment options have been investigated for the removal/reduction of drugs (e.g., antibiotics, NSAIDs, analgesics) using conventional or biological treatments, such as activated sludge processes or bio-filtration, respectively. The efficiency of these processes ranges from 20–90%. Comparatively, advanced wastewater treatment processes, such as reverse osmosis, ozonation and advanced oxidation technologies, can achieve higher removal rates for drugs. Pharmaceuticals and their metabolites undergo natural attenuation by adsorption and solar oxidation. Therefore, pharmaceuticals in water sources even at trace concentrations would have undergone removal through biological processes and, if applicable, combined adsorption and photocatalytic degradation wastewater treatment processes. This review provides an overview of the conventional and advanced technologies for the removal of pharmaceutical compounds from water sources. It also sheds light on the key points behind adsorption and photocatalysis.

Anodic oxidation of ciprofloxacin using different graphite felt anodes: Kinetics and degradation pathways

Ciprofloxacin (CIP) is ubiquitous in the environment which poses a certain threat to human and ecology. In this investigation, the physical and electrochemical properties of graphite felt (GF) anodes which affected the anodic oxidation (AO) performance, and the CIP removal effect of GF were evaluated. The GFs were used as anodes for detection of ·OH with coumarin (COU) as molecule probe and removal of CIP in a 150 mL electrolytic cell with Pt cathode (AO-GF/Pt system). The results showed that hydrophilic GF (B-GF) owned higher sp³/sp² and more oxygen-containing and nitrogen-containing functional groups than the hydrophobic GF (A-GF). Moreover, B-GF possessed higher oxygen evolution potential (1.12 V), more active sites and stronger ·OH generation capacity. Above mentioned caused that B-GF exhibited more superior properties for CIP removal. The best efficiencies (96.95%, 99.83%) were obtained in the AO-B-GF/Pt system at 6.25 mAcm^-2 after 10 min (k₁, 0.356 min^-1) and 60 min (k₂, 0.224 min^-1), respectively. Furthermore, nine degradation pathways of CIP in AO-B-GF/Pt system were summarized as the cleavage of the piperazine ring, cyclopropyl group, quinolone ring and F atom by ·OH. It provides new insights into the removal and degradation pathways of CIP with GF in AO system.

Discoloration of azo dye Brown HT using different advanced oxidation processes

In this study, known combinations of Advanced Oxidation Processes (AOPs, namely Electro-Fenton (EF), Photo-Electro-Fenton (PEF), Electro-Oxidation (EO), and EO/Ozone (O₃) were compared for the discoloration of tannery industry azo dye Brown HT (BHT). The different AOPs were tested in a 0.160 L batch electrochemical stirred thank reactor using Boron Doped Diamond (BDD) electrodes. The influence of parameters such as the current density (j) and the initial BHT concentration were to exanimated on the efficiency of all the tested processes. The oxidation tendency of EF, and PEF were compared with those of EO and O₃, based on their efficiency for BHT discoloration, which resulted as PEF > EF > EO > O₃. The AOPs showing the best oxidation performance was PEF which, using Na₂SO₄ (0.05 M) electrolyte solution and Fe²⁺ (0.5 mM), pH 3.0, j = 71 mA cm^-2, and 500 rpm process, achieved 100% discoloration and 80% chemical oxygen demand (COD) abatement after 60 min of treatment for two initial BHT concentrations (50 and 80 mg L^-1). The process accounted for a current efficiency of 30% and energy consumption 2.25 kWh (g COD)^-1 through the discoloration test. The azo dye gradually degraded, yielding non-toxic oxalic, oxamic, and glyoxylic acid, whose Fe(III) complexes were quickly photolyzed.

A binary MOF of iron and copper for treating ciprofloxacin-contaminated waste water by an integrated technique of adsorption and photocatalytic degradation

A novel MIL 53(Fe–Cu) was synthesized by a solvothermal process. This binary metal organic framework removed ciprofloxacin from waste water.

Adsorptive removal of apramycin antibiotic from aqueous solutions using Tween 80-and Triton X-100 modified clinoptilolite: experimental and fixed-bed modeling investigations

This study examined the performance of natural clinoptilolite (NC) modified with two surfactants of Triton X-100 (NC-Triton) and Tween 80 (NC-Tween) on apramycin (APR) adsorption from wastewater in batch and continues systems. The optimum pH, contact time, adsorbent dosage, and temperature were achieved. The findings revealed that the sorption was best described using the Langmuir isotherm compared to other isotherms. The maximum adsorption capacity of NC-Triton was greater than NC and NC-Tween. The lumped method was applied to solve the fixed-bed equations; predict breakthrough curve; determine axial dispersion coefficient and overall mass transfer coefficient parameters; and compare theoretical results with experimental results. Good fitness of experimental data with kinetic models of intra-particle diffusion, pseudo-first-order/liquid film diffusion and pseudo-second-order for NC, NC-Tween and NC-Triton, respectively, indicated that they were more suitable than the other models. Endothermic and spontaneous processes were resulted from positive enthalpy and negative Gibbs free energy changes, respectively.

Ciprofloxacin removal via sequential electro-oxidation and enzymatic oxidation

The combination of electro-oxidation and enzymatic oxidation was tested to evaluate the potency of this system to remove ciprofloxacin (CIP), a fluoroquinolone antibiotic, from water. For the electro-oxidation boron-doped diamond (BDD) and mixed metal oxides anodes were tested, at three current densities (4.42, 17.7 and 35.4 A/cm²). BDD anode at 35.4 A/cm² exhibited the highest removal efficiency in the shortest time (>90 % removal in 6 min). For the enzymatic oxidation, laccase from Trametes versicolor was chosen. Laccase alone was not able to remove CIP; hence the influence of redox mediators was investigated. The addition of syringaldehyde (SA) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) resulted in enhanced CIP transformation. About 48.9±4.0 % of CIP remained after 4 h of treatment when SA-mediated laccase was applied and 87.8±6.6 % in the case of ABTS-mediated laccase. The coupling of enzymatic oxidation followed by electro-oxidation led to 73 % removal of the antibiotic. Additionally, the antimicrobial activity increased up to its original efficiency after the treatment. The combination of electro-oxidation followed by enzymatic oxidation led to 97-99 % removal of CIP. There was no antimicrobial activity of the solution after the treatment. The tests with wastewater confirmed the efficacy of the system to remove CIP from the complex matrix.

Simple, fast and environmentally friendly method to determine ciprofloxacin in wastewater samples based on an impedimetric immunosensor

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater. To achieve this, an anti-ciprofloxacin antibody was immobilized on the surface of a printed carbon electrode. Then, the developed immunosensor was applied in wastewater samples from Université Laval residences (Québec, Canada) through the load transfer resistance (R_ct) using [Fe(CN)₆]^3−/4− as a redox probe, and the average CIP concentration was found to be 2.90 × 10⁻⁴ μg mL⁻¹. The observed R_ct changes presented a linear relationship from CIP concentrations of 10⁻⁵ to 1.0 μg mL⁻¹, with detection and quantification limits of 2.50 × 10⁻⁶ and 7.90 × 10⁻⁶ μg mL⁻¹, respectively. The immunosensor presented high selectivity and repeatability, as well as a good recovery rate in wastewater samples (97%). Significant interference with other compounds was not observed. The proposed method requires only 30 μL of sample without the use of organic solvents or preceding sample preparation and/or extraction techniques. Moreover, the method is fast: only 20 min of incubation followed by 2 min of analysis time was sufficient to obtain the CIP concentration. The method's estimated cost is U$ 2.00 per sample.

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater samples.

Electrochemical degradation of the antibiotic ciprofloxacin in a flow reactor using distinct BDD anodes: Reaction kinetics, identification and toxicity of the degradation products

The performances of distinct BDD anodes (boron doping of 100, 500 and 2500 ppm, with sp³/sp² carbon ratios of 215, 325, and 284, respectively) in the electrochemical degradation of ciprofloxacin - CIP (0.5 L of 50 mg L^-1 in 0.10 M Na₂SO₄, at 25 °C) were comparatively assessed using a recirculating flow system with a filter-press reactor. Performance was assessed by monitoring the CIP and total organic carbon (TOC) concentrations, oxidation intermediates, and antimicrobial activity against Escherichia coli as a function of electrolysis time. CIP removal was strongly affected by the solution pH (kept fixed), flow conditions, and current density; similar trends were obtained independently of the BDD anode used, but the BDD₁₀₀ anode yielded the best results. Enhanced mass transport was achieved at a low flow rate by promoting the solution turbulence within the reactor. The fastest complete CIP removal (within 20 min) was attained at j = 30 mA cm^-2, pH = 10.0, and q_V = 2.5 L min^-1 + bypass turbulence promotion. TOC removal was practically accomplished only after 10 h of electrolysis, with quite similar performances by the distinct BDD anodes. Five initial oxidation intermediates were identified (263 ≤ m/z ≤ 348), whereas only two terminal oxidation intermediates were detected (oxamic and formic acids). The antimicrobial activity of the electrolyzed CIP solution was almost completely removed within 10 h of electrolysis. The characteristics of the BDD anodes only had a marked effect on the CIP removal rate (best performance by the least-doped anode), contrasting with other data in the literature.

Mineralization of cefoperazone in acid medium by the microwave discharge electrodeless lamp irradiated photoelectro-Fenton using a RuO2/Ti or boron-doped diamond anode

The mineralization of 125 mL of 50-300 mg L^-1 cefoperazone (CFPZ) has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton (PEF) with a RuO₂/Ti or boron-doped diamond (BDD) anode and an activated carbon fiber (ACF) cathode. A microwave discharge electrodeless lamp (MDEL) was used as the UV source in PEF process. CFPZ decays always followed pseudo-first-order kinetics and their constant rates increased in the order: AO < EF < MDEL-PEF, regardless of anode types. Higher mineralization was achieved in all methods using BDD instead of RuO₂/Ti, while the most potent BDD-MDEL-PEF gave 88% mineralization under its optimum conditions of 0.36 A, pH 3.0 and 1.0 mmol L^-1 Fe²⁺. The synergistic mechanisms were explored by quantifying the electrogenerated H₂O₂ and formed ^•OH, in which 2.27 and 2.58 mmol L^-1 H₂O₂ were accumulated in AO-H₂O₂ with RuO₂/Ti or BDD anode, respectively, while 92.0 and 263.5 μmol L^{-1 •}OH were generated in EF with RuO₂/Ti or BDD anode, respectively. The oxidation power of EAOPs with different anodes was also compared by measuring the evolutions of NO₃^- and NH₄⁺ as well as four generated carboxylic acids including oxalic, oxamic, formic and fumaric acids.

Optimization of the electrochemical degradation process of the antibiotic ciprofloxacin using a double-sided β-PbO2 anode in a flow reactor: kinetics, identification of oxidation intermediates and toxicity evaluation

The electrochemical degradation of ciprofloxacin-CIP (50 mg L^-1 in 0.10 mol L^-1 Na₂SO₄) was investigated using a double-sided Ti-Pt/β-PbO₂ anode in a filter-press flow reactor, with identification of oxidation intermediates and follow-up of antimicrobial activity against Escherichia coli. The effect of solution pH, flow rate, current density, and temperature on the CIP removal rate was evaluated. All of these parameters did affect the CIP removal performance; thus, optimized electrolysis conditions were further explored: pH = 10, q_V = 6.5 L min^-1, j = 30 mA cm^-2, and θ = 25 °C. Therefore, CIP was removed within 2 h, whereas ~75% of the total organic carbon concentration (TOC) was removed after 5 h and then, the solution no longer presented antimicrobial activity. When the electrochemical degradation of CIP was investigated using a single-sided boron-doped diamond (BDD) anode, its performance in TOC removal was similar to that of the Ti-Pt/β-PbO₂ anode; considering the higher oxidation power of BDD, the surprisingly good comparative performance of the Ti-Pt/β-PbO₂ anode was ascribed to significantly better hydrodynamic conditions attained in the filter-press reactor used with this electrode. Five initial oxidation intermediates were identified by LC-MS/MS and completely removed after 4 h of electrolysis; since they have also been determined in other degradation processes, there must be similarities in the involved oxidation mechanisms. Five terminal oxidation intermediates (acetic, formic, oxamic, propionic, and succinic acids) were identified by LC-UV and all of them (except acetic acid) were removed after 10 h of electrolysis.

Integrated advanced oxidation process, sono-Fenton treatment, for mineralization and volume reduction of activated sludge

In this work, the efficiencies of Fenton catalytic and sonolysis processes were investigated separately and in combination together for the treatment and reduction of sludge volume. Moreover, the effects of operating parameters such as retention time, initial pH, iron concentration, and H₂O₂ concentration on COD reduction as well as the proportion of volatile solids to total solids (VS/TS) were studied. Finally, the effects of these processes on the sludge volume index (SVI) and sludge volume reduction (SVR) were evaluated. According to the results, the retention time of 60 min, pH = 3, hydrogen peroxide concentration of 0.13 M/L, and iron concentration of 2 mM/L were achieved as the optimum values. Furthermore, the SVR and SVI removal efficiencies in the Fenton process were 19% and 25%, respectively, but the removal efficiency in sonolysis process was very low and can be ignored. Under optimum conditions in sono-Fenton (SF) process, the SVR and SVI removal efficiencies were 55.7% and 83%, respectively. The results showed that by combining sonolysis and Fenton processes; due to the synergistic effect of ultrasonic waves, Fenton agent, and the production of more hydroxyl radicals; the COD removal efficiency increased to 77%, and the proportion of VS/TS in row activated sludge was reduced from 75% to 26%. Generally, by combining sonolysis and Fenton processes, the removal efficiency increased significantly as compared to separate processes owing to the production of more oxidizing agents and improving mass transfer.

Efficient removal of sulfamerazine (SMR) by ozonation in acetic acid solution after enrichment SMR from water using granular activated carbon

Sulfamerazine (SMR) as a persistent organic pollutant in waste streams is of growing environmental concern. This study explores the extraction SMR from water into an acetic acid (AA) solution using granular activated carbon (GAC), and removal of SMR by ozonation in AA solution. Systematic experiments have shown that GAC can be used as an adsorbent to transfer sulfamerazine from water to AA solution. SMR removal efficiency is 99.5% in 10% AA aqueous solution, which is better than in water. The removal rate of SMR in the AA solution decreased as the initial molar ratio of SMR and O₃ increased. The removal rate of SMR decreased with Fe³⁺ present in the reactive system. The removal of SMR is dominated by indirect ozonation in water, while the SMR removal is an effect of both direct and indirect ozonation in AA solution. It is a very efficient process for the degradation of SMR in micro polluted water when using combined GAC adsorption–desorption in AA solution and ozonation of the resulting solution.

Sulfamerazine (SMR) as a persistent organic pollutant in waste streams is of growing environmental concern.

Sorption of norfloxacin, sulfamerazine and oxytetracycline by KOH-modified biochar under single and ternary systems

Pollution of water by single antibiotics has been investigated in depth. However, in reality, a wide range of different contaminants is often mixed in the aquatic environment (contaminant cocktail). Here, single and competitive sorption dynamics of ionizable norfloxacin (NOR), sulfamerazine (SMR) and oxytetracycline (OTC) by both pristine and modified biochars were investigated. Sorption kinetics of the three antibiotics was faster in ternary-solute than single-solute system. Sorption efficiency was enhanced in the competitive system for NOR by the pristine biochar, and for OTC by both the pristine biochar and the modified biochar, while SMR sorption by the pristine biochar and the KOH-modified biochar was inhibited. Sorption was governed by electrostatic interactions, π-π EDA and H-bonds for antibiotics sorption by biochar. SMR and OTC sorption by biochar was influenced by cation bridging and surface complexation, respectively. This research finding will guide the development of treatment procedures for water polluted by multiple antibiotics.

Degradation of Chloramphenicol in Synthetic and Aquaculture Wastewater Using Electrooxidation

Chloramphenicol (CAP) is a broad-spectrum antibiotic widely used in animal farming and aquaculture industries. Despite its ban in many countries around the world, it is still used in several developing countries, with harmful effects on the surrounding aquatic environment. In this study, an electrooxidation process using a Ti/PbO anode was used to investigate the degradation of CAP in both synthetic solution and real aquaculture wastewater. A central composite design was used to determine the optimum conditions for CAP removal. Current intensity and treatment time had the most impact on the CAP removal. These two factors accounted for ∼90% of CAP removal. The optimum conditions found in this study were current intensity of 0.65 A, treatment time of 34 min, and CAP initial concentration of 0.5 mg L. Under these conditions, 98.7% of CAP removal was achieved with an energy consumption of 4.65 kW h m. The antibiotic was not present in the aquaculture wastewater, which received 0.5 mg L of CAP and was treated (by electrooxidation) under the optimum conditions. A complete removal of CAP was obtained after 34 min of treatment. According to these results, electrooxidation presents an option for the removal of antibiotics, secondary compounds, and other organic and inorganic compounds from solution.