Electrochemical oxidation can be used for decentralized wastewater treatment without the addition of chemicals. Antimony-doped tin oxide (Sb-SnO 2 : AT) provides a catalytic anode coating that is easily prepared at a relatively low cost. However, there is the potential of Sb leaching during use. To overcome this problem, a heterojunction anode is developed that uses an AT oxide layer as an ohmic contact and a nickel-doped AT oxide layer (NAT) with a substantially lower Sb content as an outer catalytic layer (NAT/AT). The two-layer NAT/AT anode has significantly longer operational lifetimes, lower Sb leaching potential, and higher activities for free radical generation and ozone production than either layer when used alone. Based on experimental results in combination with theory, an anodic ozone activation pathway at the acidic electrode/ electrolyte interface is identified as a key • OH source coupled with direct • OH production via water electrolysis. The NAT/AT anode outperforms commercial anodes (e.g., boron-doped diamond and IrO 2 ) for organic compound destruction and for microbial disinfection. The 1-log removal of carbamazepine (surface area-normalized first-order rate constant k CBZ,SA = 1.13 × 10 −3 m/s) and 5-log inactivation of E. coli and MS2 virus are achieved within 60 s in synthetic electrolytes. Even though the electrochemical efficiency is lower in the case of latrine wastewater treatment, the energy consumption (e.g., 3.9−14.0 kWh/m 3 ) is low compared to previously reported values.

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) are groundwater contaminants of emerging concern due to their toxicity and persistence. Currently, there are limited destructive treatment options for this type of water. One promising approach is electrochemical oxidation (EO) using a boron-doped diamond (BDD) anode. However, during EO treatment, chloride in water is readily converted to perchlorate (ClO 4 − ), which is an endocrine disruptor. This is a common dilemma for EO techniques: anodes with higher EO activity tend to produce more ClO 4 − . In this study, we used the BDD anode as a model anode to treat PFOA and PFOS in a chloride-bearing electrolyte. We found that the formation of ClO 4 − can be largely inhibited without compromising the efficiency of PFOA and PFOS destruction by adding hydrogen peroxide (≥50 mM H 2 O 2 ). Experimental approaches and computational kinetic modeling indicate that H 2 O 2 inhibits ClO 4− formation by quenching chlorine and hydroxyl radicals and the oxidation of PFOA and PFOS is primarily determined by direct electron transfer oxidation, regardless of the dominant radical species. This facile strategy suppressed 88% of ClO 4 − formation during EO treatment of groundwater spiked with PFOA and PFOS.

No abstract

No abstract

Hydrogen peroxide (HP) production via electrochemical oxygen reduction reaction (ORR-HP) is a critical reaction for energy storage and environmental remediation. The onsite production of high-concentration H 2 O 2 using gas diffusion electrodes (GDEs) fed by air is especially attractive. However, many studies indicate that the air–GDE combination could not produce concentrated H 2 O 2 , as the [H 2 O 2 ] leveled off or even decreased with the increasing reaction time. This study proves that the limiting factors are not the oxygen concentration in the air but the anodic and cathodic depletion of the as-formed H 2 O 2 . We proved that the anodic depletion could be excluded by adopting a divided electrolytic cell. Furthermore, we demonstrated that applying poly(tetrafluoroethylene) (PTFE) as an overcoating rather than a catalyst binder could effectively mitigate the cathodic decomposition pathways. Beyond that, we further developed a composite electrospun PTFE (E-PTFE)/carbon black (CB)/GDE electrode featuring the electrospun PTFE (E-PTFE) nanofibrous overcoating. The E-PTFE coating provides abundant triphase active sites and excludes the cathodic depletion reaction, enabling the production of >20 g/L H 2 O 2 at a current efficiency of 86.6%. Finally, we demonstrated the efficacy of the ORR-HP device in lake water remediation. Cyanobacteria and microcystin-LR were readily removed along with the onsite production of H 2 O 2 .

A novel intermittent impulsive scheme is presented to realize consensus of multi‐agent systems with time‐varying delay in this paper because intermittent impulsive control may break through the limitation of upper bound of impulsive intervals in general impulsive control in our consensus scheme. Instead of activating all the time, we introduce the intermittent impulsive control approach into the delayed multi‐agent systems where the impulsive controller is only functioned in the control windows. Based on the algebraic graph theory, the Lyapunov stability theory, and Halanay inequality matrix theory, some adequate conditions are proposed to guarantee the consensus of delayed multi‐agent systems via pinning intermittent impulsive control. Simulation results are provided ultimately to verify the validity of the proposed control mechanism.

Antibiotic resistance has become a global crisis in recent years, while wastewater treatment plants (WWTPs) have been identified as a significant source of both antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). However, commonly used disinfectants have been shown to be ineffective for the elimination of ARGs. With the goal of upgrading the conventional UV disinfection unit with stronger capability to combat ARB and ARGs, we developed a UV-assisted electrochemical oxidation (UV-EO) process that employs blue TiO2 nanotube arrays (BNTAs) as photoanodes. Inactivation of tetracycline- and sulfamethoxazole-resistant E. coli along with degradation of the corresponding plasmid coded genes (tetA and sul1) is measured by plate counting on selective agar and qPCR, respectively. In comparison with UV254 irradiation alone, enhanced ARB inactivation and ARG degradation is achieved by UV-EO. Chloride significantly promotes the inactivation efficiency due to the electrochemical production of free chlorine and the subsequent UV/chlorine photoreactions. The fluence-based first-order kinetic rate coefficients of UV-EO in Cl– are larger than those of UV254 irradiation alone by a factor of 2.1–2.3 and 1.3–1.8 for the long and short target genes, respectively. The mechanism of plasmid DNA damage by different radical species is further explored using gel electrophoresis and computational kinetic modeling. The process can effectively eliminate ARB and ARGs in latrine wastewater, though the kinetics were retarded.

No abstract