Highly efficient chloramphenicol degradation by UV and UV/H2 O2 processes based on LED light source

Electrochemical oxidation of chloramphenicol by modified Sm-PEG-PbO2 anodes: Performance and mechanism

Chloramphenicol (CAP) is used extensively in industry and daily life, but its abuse has seriously affected the environment and public health. In this paper, a new composite PbO₂ electrode was obtained through the modification Sm and polyethylene glycol (PEG), and an electrocatalytic oxidation technology of CAP degradation was investigated. The results showed that the catalytic degradation ability and industrial service life of the PEG-Sm-PbO₂ composite electrode were significantly enhanced. Co-doping inhibited the growth of grains, resulting in the formation of refined pyramidal grains on the surface of the electrode, which increased the number of active spots. The industrial service life of the modified electrode was improved by 87.0%. In addition, the degradation effect under different conditions and mechanism of CAP were also explored. The optimal conditions for CAP degradation were explored, at which time the CAP degradation rate reached 99.1%. The degradation process was in accordance with the primary reaction kinetics, and the apparent rate constant of CAP at the PEG-Sm-PbO₂ electrode was raised by 57.1% in comparison with the unmodified electrode, indicating that the modification facilitated the degradation of CAP in the electrode. Finally, two possible CAP degradation pathways were deduced. The results will provide technical support and a theoretical basis for the degradation of persistent organic pollutants.

Electrochemical oxidation of chloramphenicol with lead dioxide-surfactant composites

The PbO₂ -2 wt.% sodium dodecyl sulfate composite formed from methanesulfonate electrolyte consists of 93.1% of α-phase PbO₂ in contrast to the similar one synthesized from nitrate electrolyte, which contains 73.3% of β phase. The electrocatalytic activity of the obtained composites in the oxygen evolution reaction and oxidation of chloramphenicol was investigated. It was found that the Tafel slope significantly exceeds the theoretical value, which indicates a decrease in the degree of filling of the electrode surface with oxygen-containing particles. In the presence of organic compound and chloride ions in the solution, irreversible adsorption of the intermediate is observed, which leads to additional blocking of active centers on the oxide surface, which are involved in the oxidation of organic substance. It was established that the maximum rate of chloramphenicol conversion is 83.5% and 85% at 50 and 80 mA cm^-2 , respectively, under kinetic control. The heterogeneous oxidation rate constant of chloramphenicol is 0.0035 min^-1 . Oxidation of chloramphenicol occurs through the formation of 4-(-2-amino-1,3-dihydroxy-propanyl)-nitrobenzene with cleavage of dichloroacetic acid. Next, the amino group is oxidized to the nitro group to form 4-(2-nitro-1,3-dihydroxy-propanyl)-nitrobenzene. Subsequent electrolysis produces nitrobenzoic acid, which is oxidized to benzoic acid, later hydroquinone, then benzoquinone and a set of aliphatic compounds. PRACTITIONER POINTS: The PbO₂ -2 wt.% SDS composite consists of 93.1% of α phase of PbO₂ in contrast to those synthesized from nitrate electrolyte. The Tafel slope indicates a decrease of surface filling with oxygen-containing particles. Irreversible adsorption of the intermediate is observed in the presence of chloride ions.

Electrochemical degradation of chloramphenicol using Ti-based SnO2-Sb-Ni electrode

Antibiotic residues may be very harmful in aquatic environments, because of limited treatment efficiency of traditional treatment methods. An electrochemical system with a Ti-based SnO₂-Sb-Ni anode was developed to degrade a typical antibiotic chloramphenicol (CAP) in water. The electrode was prepared using a sol-gel method. The performance of electrode materials, impact factors and dynamic characteristics were evaluated. The Ti-based SnO₂-Sb-Ni electrode was compact and uniform as shown by characterization using SEM and XRD. The electrocatalytic oxidation of CAP was carried out in a single-chamber reactor by using a Ti-based SnO₂-Sb-Ni electrode. For 100 mg L^-1 CAP, the CAP removal ratio of 100% and the TOC removal ratio of 60% were obtained at the current density of 20 mA cm^-2 and in a neutral electrolyte at 300 min. Kinetic investigation has shown that the electro-oxidation of CAP on a Ti-based SnO₂-Sb-Ni electrode displayed a pseudo-first-order kinetic model. Free radical quenching experiments presented that the oxidation of CAP on Ti-based SnO₂-Sb-Ni electrode resulted from the synergistic effect of direct oxidation and indirect oxidation (·OH and ·SO₄^-). Doping Ni on the Ti/SnO₂-Sb electrode for CAP degradation was presented in this paper, showing its great application potential in the area of antibiotic and halogenated organic pollutant degradation.