Evaluating the electrochemical and photoelectrochemical production of hydroxyl radical during electrocoagulation process.

Highlights • First time evaluation of OH anodic production in electrocoagulation (EC) process. • First time evaluation of OH photochemical production in photoelectrocoagulation (PEC) process. • Large removal of TSS, turbidity and color from car wash wastewater by EC and PEC. • Poor TOC removal in EC and PEC, due to main action of active chlorine and Fe(OH) n. • Production of OH photochemical in electro-oxidation with Ti|IrO 2 -Ta 2 O 5 anode and UVC light. Abstract In this study, we evaluate for the first time the effect of ionic composition on the anodic production of hydroxyl radical (OH a) during electrocoagulation (EC) process in batch using carbon steel electrodes. Likewise, hydroxyl radical production from active chlorine (OH ph) electrogenerated in EC photoassisted with UVA (λ = 365 nm) and UVC light (λ = 254 nm) was evaluated using car wash wastewater. Both, OH a and OH ph , were analyzed by UV–Vis spectroscopy and fluorescence using coumarin as the probe. Under optimal conditions (j = 8 mA cm−2, 25 °C, 15 min, 6 rpm), turbidity, suspended solids and color were removed by 98.3%, 98.7% and 93.1%, respectively. However, total organic carbon (TOC) abatement only attained 27%. This can be related to the fact that OH a and OH ph were not identified during EC, with or without UV irradiation. Hence, the organic matter is mainly removed by coagulation with Fe(OH) n species. Comparative treatment of the same wastewater by electrochemical oxidation (EO) with a Ti|IrO 2 -Ta 2 O 5 anode in the presence of electrogenerated active chlorine and UVC light demonstrated the generation of OH ph , thus encouraging the potential coupling of EC with EO. [ABSTRACT FROM AUTHOR]