Removal of aqueous triclosan using TiO2 nanotube arrays reactive membrane by sequential adsorption and electrochemical degradation

Abstract

Removal of triclosan (TCS) in water has attracted increasing attention due to its high detection frequency and potential toxicity. In this study, porous TiO2 nanotube arrays (TiO2 NTA) was prepared as the reactive electrochemical membrane (REM) to adsorb aqueous TCS, and subsequently to degrade TCS in-situ (a regeneration process of TiO2 NTA). Adsorption kinetics and thermodynamic of TCS followed pseudo-second-order model and Langmuir model, respectively. Compared with adsorption at 0 mL min−1 (static adsorption), the initial adsorption rate and the maximum adsorption capacity increased 18.8-fold and 73.8-fold at 300 mL min−1, respectively. The optimal equilibrium absorption capacity (per projected area of TiO2 NTA) and the initial adsorption rate were 2042.92 mg m−2 and 108.51 mg m−2 min−1, respectively. In the subsequently electrochemical oxidation process, 99.8% of the adsorbed TCS was degraded in-situ and TiO2 NTA was regenerated simultaneously. TiO2 NTA electrode maintained the stable removal performance of TCS during four adsorption-degradation cycles. The adsorption process was a complex combination of the hydrophobic interaction and electrostatic interaction with/without applied voltage at different pH value. The electrochemical degradation pathways of TCS on TiO2 NTA were hydroxylation, disproportionation, dichlorination and cleavage of ether bond under the attack of electrochemical generated OH and O2−. The flow-through sequential adsorption and electrochemical degradation (SAED) based on TiO2 NTA REM were proved to be effective method to removal TCS in waters, especially for the water with low conductivity.