Sequential adsorption and electrochemical mineralization of gaseous toluene over CoBi-layered double hydroxide at ambient conditions

The removal of low-concentration gaseous toluene by adsorption remains challenging due to competitive adsorption by background gases, whereas conventional catalytic oxidation typically requires elevated temperatures or high energy input. In this study, we developed a sequential adsorption-electrochemical mineralization strategy for treating low-ppm toluene under ambient conditions using a cobalt-bismuth layered double hydroxide (CoBi-LDH) electrode. Structural and electrochemical analyses, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and cyclic voltammetry (CV), confirmed the formation of a layered double hydroxide structure with an interlayer spacing of 7.77 Å and robust electrochemical activity. When subjected to a 15 ppm toluene stream (20 mL min⁻¹), the CoBi-LDH electrode achieved an adsorption capacity of 2.9 mg g⁻¹, representing a removal efficiency of 69.8 %. Subsequent electrochemical oxidation at 1.0 V (vs Hg/HgO) facilitated effective mineralization, with CO₂ as the primary product and a carbon recovery of approximately 86 %. Gas chromatography–mass spectrometry (GC–MS) detected no significant aromatic intermediates post-oxidation, confirming the near complete decomposition of adsorbed toluene. Repeated adsorption–oxidation cycles exhibited consistent performance, validating the electrochemical regenerability of the electrode. This finding demonstrates the feasibility of integrating adsorption and electrochemical oxidation in a single CoBi-LDH-based platform for the efficient mitigation of low-concentration volatile organic compounds at ambient conditions.