Three-dimensionally printed scaffold coated with graphene oxide for enhanced heavy metal adsorption: Batch and fixed-bed column studies

In this study, a poly-lactic acid (PLA) filter coated with graphene oxide (GO) was three-dimensionally (3D) printed as a novel heavy metal adsorbent (particularly cadmium (Cd)) in an aqueous system. The PLA filter was extruded using the fused deposition modeling 3D printing technique, and the GO/PLA filter was prepared by simple dip coating after acetone pretreatment. The study of the adsorption of Cd onto the GO/PLA filter showed that the kinetic and isotherm experimental results were positively correlated with the pseudo-second-order equation and Langmuir model. The maximum adsorption capacity of the GO/PLA filter for Cd by Langmuir model was 1.26 mg/g. The filter could be regenerated for five repeated cycles using acid and sonication. Additionally, a continuous fixed-bed column was constructed using the GO/PLA and neat PLA filters. The Cd concentration profile was fitted to the Thomas model. The column containing the GO/PLA filter could be operated up to 1250 h until the saturation point (C0 = Ct), whereas that containing the neat PLA filter could only be used for 15 h. The GO/PLA filter also effectively adsorbed other cationic heavy metals through electrostatic attraction and strong surface complexation with oxygen-containing groups in GO. The utilization of the GO/PLA filter demonstrated not only the effective immobilization of the powdery adsorbent onto the PLA surface but also showcased the adaptability of the 3D-printed adsorption filters to water treatment.