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A laboratory scale closed-loop cycle system for the complete regeneration of sodium persulfate/sulfuric acid etching solution (SPS) has been developed by anode oxidation of sulfate paired to cathode reduction of copper. A current-efficient (110%), zero-chemical dosage and zero-emission strategy for complete regeneration of SPS and recovery of copper was achieved. The micro-etching rate of the recycled SPS has no significant difference compared with that of the fresh SPS. On average, the cost of etching in this recycling system is decreased by 100%, compared with that in the current printed circuit boards used in industries. The full utilization of spent SPS realizes waste to wealth conversion in the true sense. The developed recycling system is a techno-economically feasible, environmentally friendly, sustainable, clean and green process for the reuse of SPS and recovery of valuable metal Cu through electrooxidation of sulfate paired to electroreduction of copper. [ABSTRACT FROM AUTHOR]

Photoelectrocatalytic (PEC) process combining the merits of photocatalysis and electrocatalysis is considered as a promising ammonia oxidation technology for water treatment. However, some key issues, such as the limited in situ generation of oxidants on photoanode, slow mass transfer problem and generation of nitrate/nitrite by–products hinder the further application of PEC process in the treatment of ammonia pollutant. In this study, the graphite felt (GF) cathodes modified by different transition metals (Ni, Fe, Mn, Co, Cu) were screened by physicochemical and photoelectrochemical characterizations. The results show that the Ni–GF cathode with more Ni0 uniformly distributed on the GF surface had the best electrocatalytic activity to generate H 2 O 2. The PEC system composed of 10.0 wt% Ni–GF cathode and optimized titania nanotubes (TNTs) photoanode selectively converted about 96.1% ammonia to N 2 within 90 min. Compared with the single TNTs photoanode system, the ammonia oxidation reaction rate constant of the synergistic PEC oxidation system was increased by about two times, which demonstrated the role of the oxidants simultaneously generated on both anode and cathode. The in situ generated reactive oxygen-based oxidants and chlorine-based oxidants interacted together, and ClO• acted a leading role in the ammonia oxidation which were confirmed by quenching and probe experiments. In addition, the contributions of •OH and ClO• were significantly improved in the synergistic PEC oxidation system, compared with the single TNTs photoanode system. Furthermore, the nitrate by–products generated by the ammonia oxidation were further reduced on the Ni–GF cathode. The large amount of active chlorine and active oxygen generated on the electrode diffused into the bulk, effectively overcoming the mass transfer limitation of direct oxidation. Therefore, the developed TNTs photoanode/Ni-GF cathode system can continuously and efficiently convert ammonia to N 2 without the formation of nitrate/nitrite by–products. [Display omitted] • Ni–GF cathode with uniformly distributed Ni0 had the best electrocatalytic activity. • The coupling system presented higher ammonia removal efficiency. • Ammonia was almost completely converted to N 2 without nitrate/nitrite by-products. • Efficient ammonia oxidation was mediated by chlorine-based radicals. [ABSTRACT FROM AUTHOR]

Nowadays, it is a great challenge to minimize the negative impact of hazardous organic compounds in the environment. Highly efficient hydrogen peroxide (H 2 O 2) production through electrochemical methods with gas diffusion electrodes (GDEs) is greatly demand for degradation of organic pollutants that present in drinking water and industrial wastewater. The GDEs as cathodic electrocatalyst manifest more cost-effective, lower energy consumption and higher oxygen utilization efficiency for H 2 O 2 production as compared to other carbonaceous cathodes due to its worthy chemical and physical characteristics. In recent years, the crucial research and practical application of GDE for degradation of organic pollutants have been well developed. In this review, we focus on the novel design, fundamental aspects, influence factors, and electrochemical properties of GDEs. Furthermore, we investigate the generation of H 2 O 2 through electrocatalytic processes and degradation mechanisms of refractory organic pollutants on GDEs. We describe the advanced methodologies towards electrochemical kinetics, which include the enhancement of GDEs electrochemical catalytic activity and mass transfer process. More importantly, we also highlight the other technologies assisted electrochemical process with GDEs to enlarge the practical application for water treatment. In addition, the developmental prospective and the existing research challenges of GDE-based electrocatalytic materials for real applications in H 2 O 2 production and wastewater treatment are forecasted. According to our best knowledge, only few review articles have discussed GDEs in detail for H 2 O 2 production and their applications for degradation of organic pollutants in water. Unlabelled Image • Efficient GDE cathodes for electrogeneration of H 2 O 2 and water treatment • Fundamentals aspects, influence factors, and electrochemical properties of GDEs are discussed. • Applications of GDEs in electrochemical advanced oxidation processes are described. • The degradation mechanisms of refractory organic pollutants by GDEs are explained. • Research challenges and future perspectives of GDEs are proposed. [ABSTRACT FROM AUTHOR]

Cardiac electrophysiological heterogeneity related to the washout of acetylcholine (ACh) remains incompletely characterized. The aim of this study was to examine whether positive cardiac inotropic action is associated with electrophysiological heterogeneity between the atrium and the ventricle after ACh perfusion and washout. Epicardial monophasic action potentials (MAPs) from the right ventricle and right atrium, as well as cardiac contractility, were recorded from isolated Langendorff-perfused rabbit hearts using MAP electrodes and a force transducer. The results indicated that rebound positive inotropic actions were induced by ACh washout with adrenaline preconditioning. This effect was accompanied by an increase in MAP amplitude (MAPA) in the right ventricle but not the right atrium. These findings indicate that cholinergic muscarinic stimulation may lead to positive cardiac inotropic action followed by changes in regional electrophysiological heterogeneity between the atrial and ventricular myocardium. Therefore, we hypothesize that electrophysiological heterogeneity is an underlying cause of arrhythmogenesis as well as hemodynamic disturbance elicited by sudden termination of vagus stimulation.