Self-supporting three-dimensional CuNi-Sb-SnO2 anode with ultra-long service life for efficient removal of antibiotics in wastewater.

Electrochemical ozone production (EOP) is a promising technology for the removal of contaminants in wastewater. However, traditional two-dimensional anodes for EOP are restricted by their reliance on substrates and limited surface area, thus exhibiting poor stability and efficiency. Herein, a novel three-dimensional Sb-SnO2 with Cu and Ni co-doped (3D CuNi-ATO) was synthesized via a facile pressing-sintering method without the Ti substrate. 3D CuNi-ATO had a specific surface area two orders of magnitude higher than conventional CuNi-ATO/Ti, as well as the significant capability of EOP that differs from intrinsic 3D ATO. This endowed 3D CuNi-ATO with the capability to remove tetracycline with a pseudo-first-order rate constant of 0.033 min-1 under a low current density of 5 mA cm-2 within 120 min, which was far more efficient than that by 3D ATO and other two-dimensional anodes reported. The 3D CuNi-ATO was confirmed stable in 100 cycles and had an accelerated service lifetime of over 1100 h versus 83 h of CuNi-ATO/Ti. The degradation of tetracycline in complex matrix and flow-through reactors further revealed the promising potential of 3D CuNi-ATO to be applied in scenarios of practical application and continuous high-rate treatment.

Origin of the Activity of Electrochemical Ozone Production Over Rutile PbO2 Surfaces.

Ozonation water treatment technology has attracted increasing attention due to its environmental benign and high efficiency. Rutile PbO2 is a promising anode material for electrochemical ozone production (EOP). However, the reaction mechanism underlying ozone production catalyzed by PbO2 was rarely studied and not well-understood, which was in part due to the overlook of the electrochemistry-driven formation of oxygen vacancy (OV) of PbO2. Herein, we unrevealed the origin of the EOP activity of PbO2 starting from the electrochemical surface state analysis using density functional theory (DFT) calculations, activity analysis, and catalytic volcano modeling. Interestingly, we found that under experimental EOP potential (i. e., a potential around 2.2 V vs. reversible hydrogen electrode), OV can still be generated easily on PbO2 surfaces. Our subsequent kinetic and thermodynamic analyses show that these OV sites on PbO2 surfaces are highly active for the EOP reaction through an interesting atomic oxygen (O*)-O2 coupled mechanism. In particular, rutile PbO2(101) with the "in-situ" generated OV exhibited superior EOP activities, outperforming the (111) and (110) surfaces. Finally, by catalytic volcano modeling, we found that PbO2 is close to the theoretical optimum of the reaction, suggesting a superior EOP performance of rutile PbO2. All these analyses are in good agreement with previous experimental observations in terms of EOP overpotentials. This study provides the first volcano model to explain why rutile PbO2 is among the best metal oxide materials for EOP and provides new design guidelines for this rarely studied but industrially promising reaction.

Self-catalytic decomplexation of Cu-TEPA and simultaneous recovery of Cu by an electrochemical ozone production system using heterojunction Ni-Sb-SnO2 anode.

Heavy metal complexes from the industrial wastewater induce risks for the humans and ecosystems, yet are valuable metal resources. For energy saving and emission reduction goals, the simultaneous decomplexation and recovery of metal resources is the ideal disposal of wastewater with heavy metal complexes. Herein, a self-catalytic decomplexation scheme is developed via an electrochemical ozone production (EOP) system to achieve efficient decomplexation and Cu recovery. The EOP system could achieve 94.36% decomplexation of Cu-TEPA, which is a typical complex in catalyst industrial wastewater, and 86.52% recovery of Cu within 60 min at a current density of 10 mA/cm2. The O3 and •OH generated at the anode would first attack Cu-TEPA to produce Cu-organic nitrogen intermediates, which further catalyze O3 to generate •OH, thus self-enhancing the decomposition process in the EOP system. The released Cu2+ was gradually reduced to Cu+ and finally deposited as Cu2O and Cu to the stainless steel cathode. The technological feasibility was confirmed with other Cu-complexes such as Cu-EDTA and Cu-citrate, and the actual Cu-TEPA-containing industrial wastewater. The results provide new insights regarding the application of EOP in the simultaneous treatment of heavy metal complex wastewater and resource recovery.