Exceptional properties at the nano-scale, if appropriately harnessed, will lead to innovations in water treatment.

Adsorption is one of the most commonly used methods for the remediation of heavy metals. Generally, the spent adsorbent is regenerated using chemicals. Although chemical regeneration is efficient, it often leads to secondary wastes. To overcome such a problem, a novel remediation protocol for Cr(VI) featured with high capacity adsorption and electrochemical regeneration was carried out in this study. Experimental results showed that multiwalled carbon nanotube (MWCNT) modified carbon cloth (CC) can be used as an excellent carrier for electrodepositing polypyrrole (PPy) film, and the resultant nanocomposite termed as CC-MWCNT-PPy could be used as an adsorbent with high adsorption capacity and stability. Moreover, CC-MWCNT-PPy could be electrically regenerated to reduce secondary wastes. Desorption of Cr(VI) can be enhanced greatly by applying a reduction potential on spent CC-MWCNT-PPy. It was also observed that the Cr(VI) removal efficiency of CC-MWCNT-PPy remains almost unchanged after at least 7 cycles.

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A simple and rapid process of ReO 4 − (as a surrogate of TcO 4 − ) removal from aqueous solutions based on the electrically switched ion exchange (ESIX) method has been demonstrated in this work. Activated carbon-Polypyrrole (AC-PPy) was synthesized from activated carbon and pyrrole by electrodeposition method which was served as an electrically switched ion exchanger for ReO 4 − removal. The characterization results show that the AC-PPy composite exhibited an excellent loading capacity and a high stability for ions uptake and release. Chronoamperometric studies show that the ESIX treatment could be completed within 60 s, demonstrating the rapid uptake and release of ions. Uptake and release of ReO 4 − was verified by electrochemical quartz crystal microbalance with dissipation shift (EQCMD) studies. By modulating the electrochemical potential of the AC-PPy, the uptake and release of ReO 4 − ions can be controlled. Similar trends of uptake and release of ReO 4 − were observed in cyclic voltammetry (−0.4 to 0.8 V) for five cycles with the EQCMD. X-ray photoelectron spectroscopy (XPS) confirmed the process of ReO 4 − removal in the AC-PPy composite. Conclusively, the smart material shows excellent efficiency and selectivity for the removal of ReO 4 − from aqueous solutions.