3D printed monolithic nanocomposites as adsorbents to remove Congo red and mercury (II) from wastewater

MOFs/MXene adsorbent was prepared by in-situ growth of MOFs(ZIF-67/ZIF-8) crystal particles onto the surface and between the layers of multi-layer MXene substrate. The method followed complex separation and recovery steps after completion of adsorption and there can be a risk of secondary contamination. To avoid this, DLP technique was used to print a series of 3D printed structures (3DS) with a specific topography, the prepared MOFs/MXene composites were loaded onto surface of the structure. Polydopamine (PDA) was then coated onto the surface to prepare monolithic adsorbent (PDA/MOFs/MXene/3DS) that was easily separated and recovered. The adsorbent was characterized by SEM, XRD, FTIR, TGA and XPS, while the batch adsorption of CR and Hg (II) was performed under different experimental conditions. The optimal removal rate and maximum adsorption of the monolithic adsorbent for CR and Hg (II) were 99.13/94.10 % and 75.76/464.48 mg/g, respectively and adsorption followed chemisorption onto the surface monolayer, which was spontaneous and exothermic. Multiple cycle tests showed excellent removal of CR (82.29 %) and Hg (78.47 %). In addition, adsorbent with synergistic effects of electrostatic interactions, H-bonding and it-it stacking shows a good adsorption effect. The study proved that that PDA/MOFs/MXene/3DS is a high-strength, structurally designable, green and promising adsorbent for large-scale remediation of real contaminants frpm wastewater.