The hetero-assembly of reduced graphene oxide and hydroxide nanosheets as superlattice materials in PMS activation

Abstract

The agglomeration of rGO resulted from the morphological irregularities restrict its direct applications as catalyst for pollutants removal using advance oxidation processes (AOPs). In this study, we addressed this problem after incorporating the nanosheets of reduced graphene oxide (rGO) in the layers of hydroxides (LDHs) as Fe-rGO LDH hetero-composite. Based on the first order kinetic model, the fabricated composite showed excellent phenol removal with degradation rate constant of 0.16 min−1, 5–100 times higher than Fe-LDH/rGO or other control catalysts. This enhanced catalytic activity was resulted from the systematic assembly of both monolayered rGO and LDHs as superlattice materials, avoiding the aggregation of rGO during the reaction and thus promote the interfacial electron transfer among the active sites. Moreover, Fe-rGO LDH/PMS system exhibited consistent performance over a wide pH range (3.0 ─ 12.0) and broad spectrum of co-existing water constituents (anions and humic acid). The spectroscopic and analytical results suggested that the special arrangement of monolayered rGO in Fe-LDHs facilitated Fe sites to form a stable Fe intermediates after reacting PMS, offering a suitable centre to accept electron from another PMS to generate superoxides (•O2−). Finally, singlet oxygen (1O2) was accounted as dominant reactive oxygen species (ROS) for pollutants removal.