Electrochemical oxidation of indanthrene blue dye in a filter-press flow reactor and toxicity analyses with Raphidocelis subcapitata and Lactuca sativa

Abstract

Alternative routes to degrade dyes are of crucial importance for the environment. Hence, we report the electrochemical removal of indanthrene blue by using a boron-doped diamond anode, focusing on the toxicity of the treated solutions. Different operational conditions were studied, such as current density (5, 10, and 20 mA cm^-2) and electrolyte composition (Na₂SO₄, Na₂CO_3, and NaNO₃). Besides, the pH was monitored throughout the experiment to consider its direct influence on the ecotoxicity effects. The highest electrochemical oxidation efficiency, measured as color removal, was seen in the 180 min condition of electrolysis in 0.033 M Na₂SO₄, applying 20 mA cm^-2, resulting in a color removal of nearly 91% and 40.51 kWh m^-3 of energy consumption. The toxicity towards Lactuca sativa depends solely on pH variations being indifferent to color removal. While the inhibition concentration (IC₅₀) for Raphidocelis subcapitata increases 20% after treatment (in optimized conditions), suggesting that the byproducts are more toxic for this specific organism. Our data highlight the importance of analyzing the toxicity towards various organisms to understand the toxic effect of the treatment applied.

Keywords: Anodic oxidation; Boron-doped diamond anode; Filter-press reactor; Growth inhibition; Wastewater treatment.