Simultaneous decontamination of arsenite and antimonite using an electrochemical CNT filter functionalized with nanoscale goethite

The co-presence of arsenic (As) and antimony (Sb) in water bodies has been commonly reported. The toxicity of As and Sb varies with different speciation. Herein, we designed a dual-functional electro-chemical filter toward one-step detoxification and sequestration of highly toxic As(III) and Sb(III). The key to this technology is a functional anodic filter consists of nanoscale goethite and carbon nanotubes (CNT). Results showed that 97.9% As(III) and 91.9% Sb(III) transformation and 86.4% Astotal and 70.1% Sbtotal removal efficiency can be obtained over 2 h continuous filtration under optimized conditions. The Astotal removal kinetics and efficiency enhanced with flow rate and applied voltage (e.g., the Astotal removal efficiency increased from 62.9% at 0 V to 86.4% at 2.5 V). This enhancement in kinetics and efficiency can be explained by the synergistic effects of the flow-through design, plentiful exposed sorption sites, electrochemical reactivity, and nanoscale goethite. Moreover, the proposed technology works effectively across a wide pH range. Only negligible inhibition was observed in the presence of nitrate, chloride, and carbonate. Exhausted hybrid filters can be effectively regenerated by using chemical wash with NaOH solution. This study not only revealed the different adsorption behaviors of As(III) and Sb(III) on the hybrid filters, but also provided new insights into rational design of continuous-flow filters toward simultaneous decontamination of As(III) and Sb(III). (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A dual-functional electro-chemical filter was designed for one-step detoxification and sequestration of highly toxic As(III) and Sb(III) in water bodies. Results showed high removal efficiency under optimized conditions across a wide pH range. The technology demonstrated synergistic effects of flow-through design, exposed sorption sites, electrochemical reactivity, and nanoscale goethite.