Application of Heterojunction Ni–Sb–SnO₂ Anodes for Electrochemical Water Treatment

Abstract

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.

Electrosynthesis of >20 g/L H2O2 from Air

“…Electrochemical impedance spectroscopy (EIS) measurement was performed in the electrolyte containing 120 mM K 3 Fe(CN) 6 , 120 mM K 3 Fe(CN) 6 , and 330 mM KCl over the frequency range of 0.1 Hz to 100 kHz with a 10 mV sine wave. 23 In the study of lake water treatment, chlorophyll- a samples were filtered, extracted, and measured by a fluorometer (TD-700, Turner Designs) according to the Welschmeyer method. 24 The MC-LR was measured by a ultra-high-performance liquid chromatography (UPLC) system coupled with a triple-stage quadrupole mass spectrometer (Thermo Scientific, Vanquish-TSQ ALTIS) equipped with a Phenomenex Luna Omega PS C18 column (1.6 μm, 100 × 2.1 mm 2 ).…”

“…Absorbance at 400 nm was used to quantify [H 2 O 2 ]. Electrochemical impedance spectroscopy (EIS) measurement was performed in the electrolyte containing 120 mM K 3 Fe­(CN) 6 , 120 mM K 3 Fe­(CN) 6 , and 330 mM KCl over the frequency range of 0.1 Hz to 100 kHz with a 10 mV sine wave . In the study of lake water treatment, chlorophyll- a samples were filtered, extracted, and measured by a fluorometer (TD-700, Turner Designs) according to the Welschmeyer method .…”

Mitigation of Cyanobacterial Harmful Algal Blooms (cHABs) and Cyanotoxins by Electrochemical Oxidation: From a Bench-Scale Study to Field Application

“…to reach electrode surface was characterized by the limitingcurrent method using Fe(CN) 6 3− /Fe(CN) 6 4− as the redox pair (Figure S2). 32,35 The k m values increase with increasing flow rate (Figure 2d) due to the enhanced convective flow. The k m at the flow rate of 1.5 L/min (flux: 7377 L/(m 2 h)) is 1.16 × 10 −3 cm/ s, commensurate with those of the best-performing Ti 4 O 7 ceramics membrane electrodes ((1−1.4) × 10 −3 cm/s).…”

“…Details are summarized in Text S1. Trihalomethanes (THMs) and haloacetic acids (HAAs) were extracted following EPA methods 551.1 and 552.2 , and then analyzed by gas chromatography with electron capture detection (GC-ECD) (Agilent 7890 GC-Micro ECD) with a 30 m Rxi-5 ms column (0.25 mm i.d., 0.25 μm film thickness, Restek) …”

Quantitative Evaluations on Ozone Evolution Electrocatalysts by Scanning Electrochemical Microscopy for Oxidative Water Treatment

“…A subsequent study is warranted for NSS/SiO x (with cutting-edge OZER efficiency as herein demonstrated), to tackle the effects of wastewater compositions (target pollutants, electrolyte pH, and redox active anions among others) and operational conditions (applied current or cell voltage) on the OZER mediated water treatment efficiency. Some critical points need to be addressed more carefully for practical applications in real wastewater treatment, such as (i) leaching of metal ions from an electrocatalyst under anodization, (ii) generation of toxic halogenated byproducts including bromate, N -nitrosamine, and organoiodine compounds among others, and (iii) mechanisms of pollutant degradation by the OZER . In order to deal with O 3 -resistant pollutants, significant process intensification is expected in combination with UV irradiation or the H 2 O 2 evolution cathode to activate dissolved O 3 into free •OH.…”