Synthesizing C–N–P-tridoped TiO2 in a Salix psammophila-activated carbon body to enhance its regeneration performance

Abstract

Based on the natural interconnected pore networks of Salix psammophila (SP), TiO₂ was synthesized in an SP-based activated carbon (AC) body through a series of facile processes including impregnation, calcination, and activation. Compared with the traditional surface modification, TiO₂/AC (TiO₂ and AC composite) in this study exhibited better durability and higher regeneration performance under visible-light irradiation. There were five reasons: (1) the binding force between TiO₂ and AC was significantly enhanced, and methylene blue removal ratio only decreased by 11% after three trials; (2) C, N, and P atoms were spontaneously incorporated into the TiO₂ lattice during the synthesis processes, which observably extended the TiO₂'s visible-light response; (3) the anatase/rutile mixed phase and greater surface hydroxyl concentration elevated TiO₂ photodegradation; (4) AC being close to TiO₂ was able to trap electrons, further increasing the TiO₂'s photocatalytic activity; (5) the synergistic effect of adsorption and photodegradation was enhanced. With increasing TiO₂ content, TiO₂/AC regeneration performance was improved initially and then became weak; TiO₂/AC2 : 1 (2 : 1 is the mass ratio of tetrabutyl titanate and ethanol) exhibited the highest regeneration performance: 55% methylene blue was removed by the saturated AC after 2 h visible-light irradiation, which was almost double that of the traditional surface-modified sample.