Convex optimization for maximizing the degradation efficiency of chloroquine in a flow-by electrochemical reactor

The degradation efficiency of chloroquine phosphate (CQ), an anti-COVID-19 drug, was investigated in a flow-by electrochemical reactor (FBER) provided with two boron-doped diamond (BDD) electrodes (as cathode and anode) under batch recirculation mode. A central composite rotatable design (CCRD) was run down to model and assess the influence of initial pH in an interval of 3.71 to 11.28, the current density in an interval of 34.32 to 185.68 mA cm^-2, and liquid volumetric flow rate in an interval of 0.58 to 1.42 L min^-1, and conduct the convex optimization to obtain the maximum degradation efficiency. Experimental results were modeled through a second-order polynomial equation having a determination coefficient (R²) of 0.9705 with a variance coefficient of 1.1%. Optimal operating conditions found (initial pH of 5.38, current density (j) of 34.4 mA cm^-2, and liquid flow rate (Q) of 1.42 L min^-1) led to a global maximum degradation efficiency, COD removal efficiency, and mineralization efficiency of 89.3, 51.6 and 53.1%, respectively, with an energy consumption of 0.041 kWh L^-1 within 9 h of treatment. Additionally, a pseudo-zero-order kinetic model was demonstrated to fit the experimental data and the calculated pseudo-zero-order kinetic constant (k) was 13.14 mg L^-1 h^-1 (2.54 × 10^-5 mol dm^-3 h^-1). Furthermore, the total operating cost was of 0.47 US$ L^-1. Finally, this research could be helpful for the treatment of wastewater containing an anti-COVID-19 drug such as CQ.

The online version contains supplementary material available at 10.1007/s10008-023-05452-7.