Characterisation of Mn/Ti layered double hydroxide for methylene blue degradation with Bayesian representation of electron transport

Abstract

The exceptional electron transport mechanism involving layered double hydroxides (LDHs) have led visible light mediated photocatalysis to gain significant interest towards wastewater treatment. LDHs inherently have remarkable photocatalytic characteristics owing to their capability to vary the metal ions and its ratios in the interstitial regions, layered architecture resembling brucite, variable interlayer distance etc. The work presents the hydrothermal synthesis and characterisation of 4:1 Mn/Ti LDH, analyses the impact of Ti4+ doping with Mn2+ on the absorption edge spectra, offers insights into the basic crystal structure via data mining through cross-validation of actual XRD data, and delivers assessments of shifts in its energy density through Bayesian distribution using Markov chain Monte Carlo simulations. The characterisations indicated crystallinity; multiple narrow band-gaps; deformed hexagonally layered sheets and the presence of CO32- and H2O in the interlayer galleries of the LDH. Bayesian analyses provided 95 % credible interval estimates (CrI) for the conduction and valence band energies at varying temperature for evaluating the uncertainty of electron transport across the band-gap. Leveraging on Methylene blue (MB) photocatalysis as a test reaction, the electron transport across the LDH was investigated and it was observed that the material exhibited 92.30 % degradation at 90 min under visible light. The present study further discloses the effects of LDH concentration, time variation, solution pH, and MB concentration on the overall photocatalytic MB degradation. On the basis of the theoretical observations and experimental results, a plausible mechanistic pathway of electron transport has been presented, based on e−−h+hopping conduction model. The positive outcome of this research demonstrates the potential of Mn/Ti LDH as an effective and reusable photocatalyst for wastewater treatment processes.