Facile preparation of sepiolite@LDH composites for the visible-light degradation of organic dyes

Abstract

Sepiolite@LDH (Sep@LDH) composites were designed and prepared based on the assembly of layered double hydroxides (LDH) on acidified sepiolites (Sep) for the simultaneous photocatalytic degradation of methyl orange (MO) and methylene blue (MB). The structure, morphology, texture, optical properties, and photocatalytic performance of the prepared Sep@LDH were studied in detail. Among the Sep@LDH composites, Sep4@LDH (4.0 g Sep) exhibited the highest photocatalytic activity under visible-light irradiation, which could be attributed to its large surface area, high crystallinity, and plentiful active sites on its surface. The photodegradation of the dyes followed a pseudo first-order kinetic model (Langmuir-Hinshelwood model), indicating that the copious and homogeneous active sites on the surface of the composites contributed to the high photocatalytic activity. The photodegradation mechanism was studied by examining the active species (•OH, h+, and •O2− anions) using appropriate scavengers. It was found that •OH radicals played a critical role in the photocatalytic process of MO and MB, where the generation of •OH radicals occurred on the electron/hole (e−/h+) pairs on the surface of the Sep@LDH composites.