a-dual-functional-electroactive-filter-towards-simultaneously-sb-iii

A Dual-Functional Electroactive Filter Towards Simultaneously Sb(III) Oxidation and Sequestration

We have designed a facile method to synthesize a dual-functional electrochemical filter consisting of two 1-D materials: titanate nanowires and carbon ...

Donghua University

Herein, we rationally designed a dual-functional electroactive filter system for simultaneous detoxification and sequestration of Sb(III). Binder-free and nanoscale TiO-modified carbon nanotube (CNT) filters were fabricated. Upon application of an external electrical field, in situ transformation of Sb(III) to less toxic Sb(V) can be achieved, which is further sequestered by TiO. Sb(III) removal kinetics and capacity increase with applied voltage and flow rate. This can be explained by the synergistic effects of the filter's flow-through design, electrochemical reactivity, small pore size, and increased number of exposed sorption sites. STEM characterization confirms that Sb were mainly sequestered by TiO. XPS, AFS, and XAFS results verify that the Sb(III) conversion process was accelerated by the electrical field. The proposed electroactive filter technology works effectively across a wide pH range. The presence of sulfate, chloride, and carbonate ions negligibly inhibited Sb(III) removal. Exhausted TiO-CNT filters can be effectively regenerated using NaOH solution. At 2 V, 100 μg/L Sb(III)-spiked tap water generated ∼1600 bed volumes of effluent with >90% efficiency. Density functional theory calculations suggest that the adsorption energy of Sb(III) onto TiO increases (from -3.81 eV to -4.18 eV) and Sb(III) becomes more positively charged upon application of an electrical field.

Electroactive Modified Carbon Nanotube Filter for Simultaneous Detoxification and Sequestration of Sb(III).

One of the topics gaining lots of recent attention is the antimony (Sb) pollution. We have designed a dual-functional electroactive filter consisting of one-dimensional (1-D) titanate nanowires and carbon nanotubes for simultaneous oxidation and sorption of Sb(III). Applying an external limited DC voltage assist the in-situ conversion of highly toxic Sb(III) to less toxic Sb(V). The Sb(III) removal kinetics and efficiency were enhanced with flow rate and applied voltage (e.g., the Sb(III) removal efficiency increased from 87.5% at 0 V to 96.2% at 2 V). This enhancement in kinetics and efficiency are originated from the flow-through design, more exposed sorption sites, electrochemical reactivity, and limited pore size on the filter. The titanate-CNT hybrid filters perform effectively across a wide pH range of 3-11. Only negligible inhibition was observed in the presence of nitrate, chloride, and carbonate at varying concentrations. Our analyses using STEM, XPS, or AFS demonstrate that Sb were mainly adsorbed by Ti. DFT calculations suggest that the Sb(III) oxidation kinetics can be accelerated by the applied electric field. Exhausted titanate-CNT filters can be effectively regenerated by using NaOH solution. Moreover, the Sb(III)-spiked tap water generated ∼2400 bed volumes with a >90% removal efficiency. This study provides new insights for rational design of continuous-flow filters for the decontamination of Sb and other similar heavy metal ions.

Simultaneous oxidation and sorption of highly toxic Sb(III) using a dual-functional electroactive filter.

Being able to simultaneously reduce and adsorb highly toxic Cr(VI) from bodies of water would provide a significant advance in the treatment of water pollution. Herein, we report on the design of an electroactive filter consisting of nanoscale polyaniline modified carbon nanotubes (PANI-CNT). In an electric field, both Cr(VI) reduction kinetics and Cr(III) sorption capacity were enhanced as the flow rate and voltage increased. At pH 7, Cr(VI) removal efficiency increased from 29.3% at 0 V to 70.2% at 2.5 V. This can be ascribed to superior electrical conductivity, more available active sites and limited pore size of the PANI-CNT filter, further boosted by the flow-through operation. Due to convection-enhanced mass transport, the proposed continuous-flow PANI-CNT filter demonstrated an evidently enhanced kinetic process when compared to conventional batch system. Various advanced assessments and density functional theory calculations verified the essential role of the electric field during Cr(VI) removal. Scanning transmission electron microscopy (STEM) examinations showed that the Cr was mainly sequestered by the PANI. It was also confirmed that an exhausted PANI-CNT filter can be regenerated by chemical washing with an HCl solution. Experiments with actual Cr(VI)-contaminated electroplating wastewater further verified the effectiveness of the system, with complete Cr(VI) transformation and a 50% Cr removal efficiency at 2.5 V with a flow rate of 3 mL/min. This study provides new insights into practical continuous-flow solutions to the effective removal of highly toxic Cr(VI).

Boosting Cr(VI) detoxification and sequestration efficiency with carbon nanotube electrochemical filter functionalized with nanoscale polyaniline: Performance and mechanism.

Fuqiang Liu

Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection,
College of Environmental Science and Engineering,
Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering

Donghua University

A Dual-Functional Electroactive Filter Towards Simultaneously Sb(III) Oxidation and Sequestration