Preparation and Characterization of a Pd modified Ti/SnO 2 -Sb anode and its electrochemical degradation of Ni-EDTA

Electrochemical degradation of ciprofloxacin with a Sb-doped SnO2 electrode: performance, influencing factors and degradation pathways

Sb-doped SnO₂ electrodes were prepared with the practical sol–gel method and were used for the electrocatalytic degradation of ciprofloxacin (CIP) in aqueous solution. Results from the electrochemical characterization (including cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy) showed that the electrode with 16 coating times (SSO-16) had the highest oxygen evolution potential of 2.2 V (vs. SCE) and the highest electrochemically active area of 3.74 cm². The results of scanning electron microscopy and X-ray diffraction showed that the coating times could affect the surface morphology and crystal structure of the electrodes, and the SSO-16 electrode had a denser surface, higher crystallinity, and smaller grain size (28.6 nm). Moreover, the experimental parameters for CIP degradation with SSO-16 were optimized, and the removal ratio of CIP reached to almost 100% within 60 min. In addition, the possible degradation pathways of CIP were proposed. And the stability and reusability of the SSO-16 electrode were also studied. These results are valuable for the preparation of high electrocatalytic performance electrodes by a sol–gel coating method for electrochemical degradation of antibiotics.

Sb-doped SnO₂ electrodes with different coating times were prepared by an optimum sol–gel method and the application on the electrocatalytic degradation of ciprofloxacin in aqueous solution were investigated.

Enhanced oxidation potential of Ti/SnO2-Cu electrode for electrochemical degradation of low-concentration ceftazidime in aqueous solution: Performance and degradation pathway

In order to develop an efficient electrode to remove pharmaceutical and personal care products from wastewater, copper and antimony doped Ti/SnO₂ electrode were prepared by thermal decomposition. Electrochemical characterization was undertaken on Ti/SnO₂-Cu using cyclic voltammetry and linear sweep voltammetry, indicating an ultra-high 2.1 V of oxygen evolution potential, better stability, and superior corrosion resistance rather than traditional Ti/SnO₂-Sb electrode. Competitive degradation experiments showed more efficient removal rate was achieved on Ti/SnO₂-Cu electrode, which could remove more than 90% ceftazidime within 60 min. The microstructure and crystal orientation of the modified electrodes were investigated by scanning electron microscopy, which indicated that the crystal of the Ti/SnO₂-Cu electrode grew in more porous and uniform condition, covered with closely arranged layers of the coating. X-ray photoelectron spectroscopy and X-ray diffractions suggested that Cu₂O was successfully coated on the Ti/SnO₂-Cu electrode surface. The operating parameters of electrochemical degradation process were also investigated, including current density, initial concentration, electrode distance, stirring rate and supporting electrolyte. Consequently, the intermediate products of electrochemical degradation were monitored by liquid chromatography-mass spectrometry and a major degradation pathway was proposed.

Co-N-doped MoO2 modified carbon felt cathode for removal of EDTA-Ni in electro-Fenton process

Metal ions removal is inhibited in aqueous solution containing ethylenediaminetetraacetic acid (EDTA). In this study, the non-noble metals-based Co-N-doped MoO₂ nanowires (Co-N-MoO₂) were successfully synthesized using cyanamide and Co(Ac)₂ as precursors by pyrolysis, then immobilized on carbon felt (CF), and firstly used as cathode to remove EDTA-Ni complex through oxygen reduction reaction (ORR) in electro-Fenton (EF) process. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicated that a synergetic coupling effect of doping of N and Co induced structural modifications of MoO₂ lattice, and produced more lattice defects. The electrochemical analysis results showed that the superior ORR electrochemical catalysis activities were obtained at pH = 3 with the lowest cathodic peak potentials (- 0.157 V vs. Ag/AgCl), the highest electrochemical active surface area (EASA: 3.971 mC cm^-2), the extraordinarily high of the ring current (35.5 μA) and high H₂O₂ yield (> 20%). Under the optimum conditions, about 68% of EDTA-Ni was removed with the Co-N-MoO₂/CF as cathode after 120 min with lower specific energy consumption (0.0226 kW h mg^-1 (DOC)) in EF system. Mechanism analysis indicated that the production of strong oxidizing property of hydroxyl radical (•OH) on the cathode played an important role in the removal of EDTA-Ni in the EF process, synergetic effect of cobalt and nitrogen co-doped could facilitate the high generation of H₂O₂, which greatly promote the formation of •OH. The EF system with Co-N-MoO₂/CF cathode has a potential for breaking metal-complex with good stability, showing that this cathode is a candidate for application for applications in EAPOs.

Effect of calcination temperature on the properties of Ti/SnO2-Sb anode and its performance in Ni-EDTA electrochemical degradation

Pd-doped Ti/SnO₂-Sb anode was prepared at different calcination temperatures by a wet-impregnation method and employed in simultaneous electrochemical catalytic degradation of Ni-EDTA and recovery of nickel. The results showed that Ti/SnO₂-Sb-Pd-500 could achieve the highest electrochemical activity (87.5% of Ni-EDTA removal efficiency), superior durability (50.7 h of accelerated lifetime), and higher Ni recovery (19.8%) on cathode. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis suggested that Ni-EDTA degradation on anode was mainly indirect oxidation-controlled reaction, attributing to the high oxide state of MO_X + 1 and MO_X(·OH), rather than direct oxidation. Scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses indicated that calcination temperature could modify the morphology of electrode surface and affect the incorporation and valence state transformation of metal species (Sb and Pd) in SnO₂ lattice. Ti/SnO₂-Sb-Pd-500 achieved the highest electrochemical capacity with the highest levels of adsorbed oxygen O_ads/E_T (27.11%) and lattice oxygen O_lat/E_T (29.69%). Moreover, the operation conditions for Ni-EDTA electrochemical degradation were optimized. These findings were valuable for developing a high-performance electrode for Ni-EDTA electrochemical degradation.

In-situ synthesis of 3D GA on titanium wire as a binder- free electrode for electro-Fenton removing of EDTA-Ni

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. The three-dimensional (3D) macroporous graphene aerogels (GA), which was in-situ assembled by reduced graphene oxide (rGO) sheets on titanium wire as binder-free electrode, was presented as cathode for the degradation of EDTA-Ni in Electro-Fenton process. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Brunauer-Emmett-Teller (BET) results indicated 3D GA formed three dimensional architecture with large and homogenous macropore structure and surface area. Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV) and Rotating Ring-disk Electrode (RRDE) results showed that the 3D GA cathode at pH 3 displayed the highest current density and electrochemical active surface area (ECSA), and better two-electron selectivity for ORR than other pH value, confirming the 3D-GA cathode at pH 3 has the highest electrocatalytic activity and generates more H₂O₂. The factors such as pH, applied current density, concentration of Fe²⁺, Na₂SO_4, and aeration rates of air were also investigated. Under the optimum conditions, 73.5% of EDTA-Ni was degraded after reaction for 2h. Mechanism analysis indicated that the production of OH on the 3D GA cathode played an important role in the removal of EDTA-Ni in the 3D GA-EF process, where the direct regeneration of Fe²⁺ on the cathode would greatly reduce the consumption of H₂O₂. Therefore, it is of great promise for 3D-GA catalyst to be developed as highly efficient, cost-effective and durable cathode for the removal of EDTA-Ni.