The rapid coagulation of graphene oxide on La-doped layered double hydroxides

Abstract Since graphene oxide (GO) has been found to be one of the toxic graphene-based nanomaterials, the environmental behavior of GO has been studied extensively in aqueous solution systems. In this work, the large ionic radius lanthanum (La) was doped onto the layered double hydroxides (LDHs), which was conducive to remove the negatively charged GO. The results showed that the coagulation of GO on La-doped LDHs was dependent on pH and the types of electrolytes. After calcined at 400 °C for 4 h, the maximum GO removal capacities could reach 565.8 mg/g on Mg/Al/La-CLDHs and 558.6 mg/g on Ca/Al/La-CLDHs at GO initial concentration of 120 mg/L and LDHs content of 0.2 g/L. The short equilibrium time and high removal capacity suggested the huge advantage of LDHs in practical applications. More importantly, the La-doped LDHs could still exhibit high removal capacities after five cycles, indicating that the La-doped LDHs hold good reusability and could be used for GO pollution cleanup from water. The coagulation of GO on La-doped LDHs was mainly dominated by electrostatic attraction and hydrogen bond. These findings were useful to understand the environmental fate and transport of GO nanoparticles in aqueous systems.