Direct electron transfer for catalytic ozonation with Mn₃Al₂(SiO₄)₃ ceramic membranes to achieve rapid water...

A solid-phase synthesis Mn₃Al₂(SiO₄)₃ ceramic membrane (MnAl membrane) was designed to overcome the inherent limitations of low catalyst activity and inefficient mass transfer in heterogeneous catalytic ozonation processes. Reactive oxygen species (ROS) generated from the activation of ozone were confined within the nanochannel to facilitate mass transfer. Compared with the 0-MnAl membrane, the 10-MnAl membrane exhibited excellent removal efficiency for 2,4-D, with a 29-fold enhancement in the pseudo first-order kinetic constant. The contribution of ROS to 2,4-D removal was quantified with a competitive kinetic model, with 90.1 % attributed to ·OH. Isotope and electrochemical measurements, combined with density functional theory calculations, demonstrated that Mn atoms serve as active sites to facilitate the adsorption and activation of ozone via direct electron transfer. The density of states and the relative free energy of ROS generation were explored. The effects of nanochannel confinement and the density of active sites on the removal efficiency were revealed via multiphysics finite element simulations, which confirmed that the optimal ratio for solid-phase synthesis was 10 %. The ·OH catalytic layer ratio of the 10-MnAl membrane reached 24.6 %. This study revealed the nanochannel confinement and electron transfer process, thereby offering findings that provide novel insights into the design of catalytic ceramic membranes and the application of HCO in water treatment.