Linearly Scaled-up Plasma–Water Biphasic DBD Microreactors: Application to Hydrogen Peroxide Synthesis and Water Decontamination

We previously demonstrated that a modular biphasic liquid water/helium plasma reactor can efficiently produce hydrogen peroxide (H2O2). Here we demonstrate that by increasing the reactor length and thus the residence time or the applied plasma power, we can increase the outlet H2O2 concentration in the aqueous phase (an example of 39 mM is showcased) while using an argon plasma. By introducing spatially resolved optical emission spectroscopy (OES), we reveal an increasing water-produced ·OH radical concentration along the tubular reactor and correlate the ·OH production with the H2O2 concentration. High peroxide concentrations achieved through a straightforward linear reactor scale-up are suitable for green partial oxidation reactions and biochemical and environmental decontamination. This potential is exemplified by showcasing the complete and ultrafast continuous flow decolorization of an aqueous solution of highly concentrated (300 mg L–1) methylene blue (MB).