Porous Ti/SnO2-Sb anode as reactive electrochemical membrane for removing trace antiretroviral drug stavudine from wastewater.

Electrochemical degradation of trace antiretroviral drug stavudine was investigated by using a reactive electrochemical membrane (REM) with Ti/SnO2-Sb anode. From the results it was evident that the stavudine degradation followed pseudo-first-order kinetics, with the values of the degradation rate constant and half-life being 0.24 min-1 and 2.9 min, respectively, at a current density of 8 mA cm-2. The degradation rate was obviously decreased under alkaline condition (pH = 11.0) and the degradation was also inhibited in the presence of NO3- and Cl-. Five intermediates were identified in the electrochemical degradation of stavudine, and the degradation pathways were proposed. Density functional theory calculation revealed that the double bond carbon atom nearby hydroxymethyl group was the site attacked by OH and the cleavage of CN bond was the rate-determining step in the electrochemical degradation of stavudine. The nitrogen in stavudine was mainly converted to nitrate and ammonium. Quantitative structure-activity relationship model indicated that the toxicity of some intermediates was higher than the parent compound stavudine. The electric energy consumption for 90% stavudine degradation ranged from 0.87 to 2.29 Wh L-1 at the experimental conditions, indicating that stavudine can be degraded efficiently by the REM with Ti/SnO2-Sb anode.