Fabrication of a permeable SnO2-Sb reactive anodic filter for high-efficiency electrochemical oxidation of antibiotics in wastewater

Chao Yang; Yiang Fan; Shanshan Shang; Pu Li; Xiao-Yan Li

doi:10.1016/j.envint.2021.106827

Fabrication of a permeable SnO₂-Sb reactive anodic filter for high-efficiency electrochemical oxidation of antibiotics in wastewater

Environ Int. 2021 Dec:157:106827. doi: 10.1016/j.envint.2021.106827. Epub 2021 Aug 18.

Authors

Chao Yang¹, Yiang Fan¹, Shanshan Shang², Pu Li¹, Xiao-Yan Li³

Affiliations

¹ Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
² School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
³ Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; Tsinghua-Berkeley Shenzhen Institute, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China. Electronic address: xlia@hku.hk.

PMID: 34418849
DOI: 10.1016/j.envint.2021.106827

Abstract

Electrochemical oxidation (ECO) is an appealing technology for treating emerging organic pollutants in wastewater. However, the conventional flow-by ECO process is expensive with a low energy efficiency owing to the limitations of mass transport of contaminants to the limited surface area of the anode. In this study, a novel freestanding porous and permeable SnO₂-Sb anode was fabricated by one-step sintering using micrometer-sized (NH₄)₂CO₃ grains as the pore-forming agents. This permeable SnO₂-Sb anode without Ti substrate functioned as a reactive anodic filter (RAF) in an ECO cell to treat wastewater containing ciprofloxacin (CIP). Forcing the wastewater through the porous RAF depth-wise improved the mass transport and vastly enlarged the electroactive surface area. Compared with the conventional flow-by configuration, the flow-through RAF exhibited a 12-fold increase in the mass transfer rate constant (60.7 × 10^-6 m s^-1) and a 5-fold increase in the CIP degradation rate constant (0.077 min^-1). At a cell potential of 4.0 V, more than 92% of the CIP was degraded in a single-pass operation at a filtration flux of 54 L m^-2 h^-1 and a short retention time of 1.7 min through the RAF. The robustness and stability of the RAF were demonstrated by its remarkable CIP degradation efficacy of 99% during 200 h of operation. The mechanism of CIP degradation was examined using probe molecules and density functional theory calculations and found to be a combined effect of direct electron transfer and oxidation by generated radicals (OH and SO₄^-). The great potential of RAF in flow-through ECO was further validated by its effective removal (>92%) of various organic pollutants in actual municipal wastewater at a low energy consumption of 0.33 kWh m^-3. The RAF-based ECO process thus provides an advanced environmental technology for the oxidation of toxic and recalcitrant organic pollutants in wastewater treatment.

Keywords: 3D porous electrode; Antibiotic wastewater; Ciprofloxacin; Electrochemical treatment; Flow through; Reactive filter.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anti-Bacterial Agents
Electrodes
Oxidation-Reduction
Titanium
Wastewater
Water Pollutants, Chemical* / analysis
Water Purification*

Substances

Anti-Bacterial Agents
Waste Water
Water Pollutants, Chemical
Titanium