A comparative study on the mineralization of waste butyl acetate by electrochemical oxidation via persulphate/hypochlorite and silver (II) reagents using DSA® anodes: Statistical optimization by response surface methodology

Abstract

AbstractMediated electrochemical oxidation of butyl acetate (BA) in wastewater was conducted by employing two different techniques based on S2O8−2/ClO− and Ag (II) reagents using commercial Dimensionally Stable Anode (DSA)®‐O2 or DSA®‐Cl2 anodes. Response surface methodology (RSM) was also engaged to investigate process parameters impacts and their interactions on BA mineralization efficiency and energy consumption. Fourier‐transform infrared spectroscopy (FT‐IR), UV–visible, and gas chromatography (GC) analyses confirmed BA mineralization and the optimum removal conditions were then attained for both systems. Chemical oxygen demand (COD) analysis showed that electro‐oxidation by mixed persulphate/hypochlorite oxidants favours the mineralization of BA (99.7%) compared to the Ag (II) technique (96.56%). The higher removal efficiency obtained by S2O8−2/ClO− was achieved in a neutral aquatic medium using DSA®‐Cl2 at a lower current density (CD), temperature, and electrolysis time (pH: 6, CD: 0.1 kA/m2, and time: 60 min) compared to those obtained by Ag (II) ions (pH: ≤3, CD: 1.69 kA/m2, and time: 130 min). The former process occurred under the charge transfer control mechanism at low CDs, whereas at an elevated CD (about 1.0 kA/m2), mass transfer was predominant due to the parasitic oxygen evolution. On the other hand, the latter process was found charge transfer‐controlled at low BA concentrations (≤200 ppm), whereas it turned out mass transfer‐controlled at higher BA concentrations. Comparing the anode type, energy consumption for BA mineralization by S2O8−2/ClO− ions using DSA®‐Cl2 at the optimum conditions was 0.009 kW · h/dm3, which was about three times lower than that of the DSA®‐O2 anode.