A novel activated sludge-graphene oxide composites for the removal of uranium(VI) from aqueous solutions

An immobilization approach for the fabrication of activated sludge-graphene oxide composites (AS-GO) was proposed in this work in order to make full use of the adsorption feature of activated sludge and graphene oxide. The influence of solution pH, reaction time and uranium concentration on uranium adsorption behavior from aqueous solutions by AS-GO prepared were examined in detail. The maximum adsorption capacity of AS-GO toward uranium achieved as 180.6 ± 4.6 mg/g. The characteristics of uranium adsorption by AS-GO were studied via kinetics and isotherm studies, the results exhibited that this adsorption behavior could be well described by the Langmuir isotherm and the pseudo-second-order kinetic model, which indicated that a monolayer adsorption occurred on AS-GO and the chemisorption was the main rate-limiting step. The adsorption mechanism of uranium by AS-GO involved electrostatic attractions and inner-sphere complexation between uranium and the oxygen as well as nitrogen-containing groups. This work shows that AS-GO has great potential to be used as a novel adsorbent for the efficient uranium adsorption from aqueous solutions.