Scaling-up of microbial electrosynthesis with multiple electrodes for in situ production of hydrogen peroxide

Abstract

Microbial electrosynthesis system (MES) has recently been shown to be a promising alternative way for realizing in situ and energy-saving synthesis of hydrogen peroxide (H₂O₂). Although promising, the scaling-up feasibility of such a process is rarely reported. In this study, a 20-L up-scaled two-chamber MES reactor was developed and investigated for in situ and efficient H₂O₂ electrosynthesis. Maximum H₂O₂ production rate of 10.82 mg L^-1 h^-1 and cumulative H₂O₂ concentration of 454.44 mg L^-1 within 42 h were obtained with an input voltage of 0.6 V, cathodic aeration velocity of 0.045 mL min^-1 mL^-1, 50 mM Na₂SO₄, and initial pH 3. The electrical energy consumption regarding direct input voltage was only 0.239 kWh kg^-1 H₂O₂, which was further much lower compared with laboratory-scale systems. The obtained results suggested that the future industrialization of MES technology for in situ synthesis of H₂O₂ and further application in environmental remediation have broad prospects.

Keywords: biotechnology; electrochemistry; engineering; materials science.

Graphical abstract

Figure 1

Feasibility verification of this 20-L scaled-up MES reactor regarding H₂O₂ production Operating conditions: input voltage of 0.6 V, cathode aeration velocity of 0.045 mL min⁻¹ mL⁻¹, initial catholyte pH of 3, and electrolyte nature and concentration of 50 mM Na₂SO₄, respectively. Control 1: without cathodic aeration. Control 2: open circuit. Control 3: without input voltage.

Figure 2

Effect of input voltage (A) H₂O₂ production and (B) current efficiency in the scaled-up reactor. Operating conditions: cathode aeration velocity of 0.045 mL min⁻¹ mL⁻¹, initial catholyte pH of 3, and electrolyte nature and concentration of 50 mM Na₂SO₄, respectively.

Figure 3

Effect of cathodic aeration velocity (A) H₂O₂ production and (B) current efficiency in the scaled-up MES reactor. Operating conditions: input voltage of 0.6 V, initial catholyte pH of 3, and electrolyte nature and concentration of 50 mM Na₂SO₄, respectively.

Figure 4

Effect of initial catholyte pH (A) H₂O₂ production, (B) current efficiency in the scaled-up MES reactor, and (C) pH variation during the process. Operating conditions: input voltage of 0.6 V, cathodic aeration velocity of 0.045 mL min⁻¹ mL⁻¹, and electrolyte nature and concentration of 50 mM Na₂SO₄, respectively.

Figure 5

Effect of electrolyte nature and concentration (A and C) H₂O₂ production and (B and D) current efficiency in the scaled-up MES reactor. Operating conditions: input voltage of 0.6 V, cathodic aeration velocity of 0.045 mL min⁻¹ mL⁻¹, and electrolyte nature (NaCl, Na₂SO₄ and Na₂CO₃), and initial Na₂SO₄ concentration of 10, 25, 50, and 100 mM, respectively.