Photocatalytic performance of Ti/MMO/ZnO at degradation of levofloxacin: Effect of pH and chloride anions

Highly stable Ag-doped Cu2O immobilized cellulose-derived carbon beads with enhanced visible-light photocatalytic degradation of levofloxacin

Ag-doped Cu2O immobilized carbon beads (Ag/Cu2O@CB) based composite photocatalysts have been prepared for the removal of levofloxacin, an antibiotic, from water. The photocatalysts were prepared by the processes of chemical reduction and in-situ solid-phase precipitation. The composite photocatalyst was characterized by a porous and interconnected network structure. Ag nanoparticles were deposited on Cu2O particles to develop a metal-based semiconductor to increase the catalytic efficiency of the system and the separation efficiency of the photogenerated carriers. Cellulose-derived carbon beads (CBs) can also be used as electron storage libraries which can capture electrons released from the conduction band of Cu2O. The results revealed that the maximum catalytic degradation efficiency of the composite photocatalyst for the antibiotic levofloxacin was 99.02 %. The Langmuir-Hinshelwood model was used to study the reaction kinetics, and the process of photodegradation followed first-order kinetics. The maximum apparent rate was recorded to be 0.0906 min-1. The mass spectrometry technique showed that levofloxacin degraded into carbon dioxide and water in the presence of the photocatalyst. The results revealed that the easy-to-produce photocatalyst was stable and efficient in levofloxacin removing.

Contribution of electrolyte in parametric optimization of perfluorooctanoic acid during electro-oxidation: Active chlorinated and sulfonated by-products formation and distribution

The present study investigated the roles of peroxydisulfate (PDS) radicals and sulfate radicals (SO₄^•-) that formed from sulfate (SO₄^2-) during electrochemical oxidation of perfluorooctanoic acid (PFOA). The effect of operating parameters such as different types of electrolytes (NaCl, NaClO₄, and Na₂SO₄), initial pH, current density, dose of electrolyte, and initial concentration of PFOA using electrochemical oxidation for perfluorooctanoic acid (PFOA) decomposition study was investigated. A difference in the removal efficiency with different electrolytes (i.e., Cl^-, ClO₄^-, and SO₄^2-) illustrated an increasing effect of electrooxidation of PFOA in the order of ClO₄^- < Cl^- < SO₄^2-, which suggested that ^•OH induced oxidation and direct e^- transfer reaction continued to play a crucial role in oxidation of PFOA. At the optimum treatment condition of j = 225.2 Am^-2, Na₂SO₄ concentration = 1.5 gL^-1, [PFOA]_o = 50 mgL^-1 and initial pH = 3.8 maximum PFOA removal of 92% and TOC removal of 80% was investigated at 240 min. The formation of three shorter-chain perfluorocarboxylates (i.e., perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), and perfluoropentanoic acid (PFPeA) and formate (HCOO^-) ions were detected as by-products of PFOA electro-oxidation, showing that the C-C bond first broken in C₇F₁₅ and then mineralized into CO₂, and fluoride ion (F^-). The fluorine recovery as F^- ions and the organic fluorine as the shorter-chain by-products were also obtained. The degradation kinetic has also been studied using the nth-order kinetic model.

Electro-Fenton-Based Technologies for Selectively Degrading Antibiotics in Aqueous Media

The viability of the Electro-Fenton (EF) process in the selective degradation of penicillin G (PenG) in complex solutions has been studied. The role of the anode material (boron-doped diamond (BDD) or mixed metal oxide (MMO)) and the cathode 3D support (foam or mesh), as well as the synergistic effect of UVC light irradiation (photoelectron-Fenton, PEF), have been evaluated. The results show that Pen G can be efficiently and selectively removed by EF, obtaining higher PenG removal rates when using the BDD anode (100%) than when using the MMO anode (75.5%). Additionally, mineralization is not favored under the experimental conditions tested (pH 3, 5 mA cm−2), since both aromatic and carboxylic acids accumulate in the reaction system as final products. In this regard, the EF-treated solution presents a high biological oxygen demand and a low percentage of Vibrio fischeri inhibition, which leads to high biodegradability and low toxicity of this final effluent. Furthermore, the combination with UVC radiation in the PEF process shows a clear synergistic effect on the degradation of penicillin G: 166.67% and 83.18% using MMO and BBD anodes, respectively. The specific energy required to attain the complete removal of PenG and high inhibition of the antibiotic effect is less than 0.05 Ah dm−3. This confirms that PEF can be efficiently used as a pretreatment of conventional wastewater treatment plants to decrease the chemical risk of complex solutions polluted with antibiotics.

A comprehensive review on recent advances toward sequestration of levofloxacin antibiotic from wastewater

Among various classes of antibiotics, fluoroquinolones, especially Levofloxacin, are being administered on a large scale for numerous purposes. Being highly stable to be completely metabolized, residual quantities of Levofloxacin get accumulated into the food chain proving a great global threat for aquatic as well as terrestrial ecosystems. Various removal techniques including both conventional and advanced methods have been reported for this purpose. This review is a novel attempt to make a critical analysis of the recent advances made exclusively toward the sequestration of Levofloxacin from wastewater through an extensive literature survey (2015-2021). Adsorption and advanced oxidation processes especially photocatalytic degradation are the most tested techniques in which assorted nanomaterials play a significant role. Several photocatalysts exhibited up to 100% degradation of LEV which makes photocatalytic degradation the best method among other tested methods. However, the degraded products need to be further monitored in terms of their toxicity. Biological degradation may prove to be the most environment-friendly with the least toxicity, unfortunately, not much research is reported in the field. With these key findings and knowledge gaps, authors suggest the scope of hybrid techniques, which have been experimented on other antibiotics. These can potentially minimize the disadvantages of the individual techniques concurrently improving the efficiency of LEV removal. Besides, techniques like column adsorption, membrane treatment, and ozonation, being least reported, reserve good perspectives for future research. With these implications, the review will certainly serve as a breakthrough for researchers working in this field to aid their future findings.

Photoelectrocatalytic treatment of levofloxacin using Ti/MMO/ZnO electrode

Here, the antibiotic levofloxacin (LFX) widely used and detected in the environment was degraded by photoelectrolysis using a new electrode based on zinc oxide (ZnO) and a mixture of mixed oxides of ruthenium and titanium (MMO). The influence of the potential and irradiation of UV light was investigated in the photostability of the Ti/MMO/ZnO electrode and in the degradation of the antibiotic. The experiments were conducted at different pH values (5.0, 7.0 and 9.0) in sodium sulfate solution in a glass reactor with central lighting. It was observed that the new Ti/MMO/ZnO electrode has good stability under light irradiation and potential, presenting excellent photocurrent and high photoactivity in LFX photoelectrolysis. The removal efficiency of the compound was directly related to the formation of oxidizing species in solution, the photo-generated charges on the electrode and the electrostatic characteristics of the molecule. The mineralization rate, the formation of reaction intermediates and short chain carboxylic acids (acetic, maleic, oxalic and oxamic acid), in addition to the formation of N-mineral species (NO₃^- and NH₄⁺) was dependent on the pH of the solution and the investigated processes: photoelectrolysis was more efficient than photolysis, which, in turn, was more efficient than electrolysis. The synergistic effect and the high rate of degradation of LFX after 4.0 h of treatment (100%) observed in photoelectrolysis at alkaline pH, was associated with the high stability of the Ti/MMO/ZnO electrode at this pH, the photoactivation of sulfate ions and the ease generation of oxidizing radicals, such as OH.

Electrocatalytic Degradation of Levofloxacin, a Typical Antibiotic in Hospital Wastewater

Presently, in the context of the novel coronavirus pneumonia epidemic, several antibiotics are overused in hospitals, causing heavy pressure on the hospital’s wastewater treatment process. Therefore, developing stable, safe, and efficient hospital wastewater treatment equipment is crucial. Herein, a bench-scale electrooxidation equipment for hospital wastewater was used to evaluate the removal effect of the main antibiotic levofloxacin (LVX) in hospital wastewater using response surface methodology (RSM). During the degradation process, the influence of the following five factors on total organic carbon (TOC) removal was discussed and the best reaction condition was obtained: current density, initial pH, flow rate, chloride ion concentration, and reaction time of 39.6 A/m², 6.5, 50 mL/min, 4‰, and 120 min, respectively. The TOC removal could reach 41% after a reaction time of 120 min, which was consistent with the result predicted by the response surface (40.48%). Moreover, the morphology and properties of the electrode were analyzed. The degradation pathway of LVX was analyzed using high-performance liquid chromatography–mass spectrometry (LC–MS). Subsequently, the bench-scale electrooxidation equipment was changed into onboard-scale electrooxidation equipment, and the onboard-scale equipment was promoted to several hospitals in Dalian.