Insights into the synthesis of monolithic and structured graphene bulks and its application for Cu2+ ions removal from aqueous solution

Abstract

Graphene oxide (GO) was a promising adsorbent for the contaminants removal in the wastewater. However, the nanoscale GO with the properties of easy agglomeration and difficult to separate in the solution severely restricted its widespread practical application. Therefore, a monolithic and structured GO bulk was prepared by a 3D printing method and used as adsorbent for the removal of Cu2+ ions. The rheological property and printability of the ink, as well as the mechanical property and adsorption capacity of the printed GO bulk were investigated. It was found that the optimal ratio of GO: sodium alginate was 1.5:2.0 with the compressive strength was 6.23 MPa. Batch experiments exhibited that the Cu2+ sorption was an endothermic reaction and the maximum adsorption capacity calculated by Langmuir model was 179.32 mg/g at 303.15 K. Kinetics, FTIR and XPS analysis revealed that the mechanism of Cu2+ adsorption was mainly a chemical dominated process involving the oxygen functional groups contained in GO and sodium alginate. The desorption and regeneration test results indicated that the printed GO bulk was an ideal adsorbent for heavy metals removal in real applications due to its excellent adsorption capacity and convenient recycling performance.