Synthesis of conch-like layered carbon nanosheets by ball-milling assisted ultrasonic exfoliation for highly selective removal of Cd(II) from multiple water matrices

Development of carbonaceous materials from biomass have attracted tremendous research interest because of their intriguing physicochemical properties and promising applications. However, endowing them with precisely controlled morphologies remains a formidable challenge. Herein, oxygen-functionalized biomass-derived carbon-nanosheets (CNSs) framework was synthesized using ball-milling ultrasonic exfoliation for their application to remove cadmium Cd(II) from water matrices. The obtained CNSs showed remarkably higher surface area (368.9 m2 g-1), thickness-range (∼6-8 nm) and pore size (10.58 nm) than pristine carbon (PC) (10.126 m2 g-1, 1-2 µm and 2.13 nm, respectively). CNSs demonstrated higher adsorption capacity (545.76 mg g-1), superior reusability (removal efficiency maintained >91% after 10 cycles) and excellent selectivity (Kd = 4.7 × 106 mL g−1). The adsorption isotherm and kinetics data were better fitted by Langmuir and pseudo-second order models. High adsorption selectivity of CNSs led to 97.7% Cd(II) adsorption in presence of Cu(II), Zn(II), Pb(II) and Ni(II) ions. The strong efficiency of CNSs was also evident in complex water matrices including tap water, groundwater (Cd(II) removal of >99%) and river water (98.97%). The experimental analyses indicate that electrostatic attraction and surface complexation as the prominent adsorption mechanisms. Overall, this work illustrates an applicable strategy to develop carbon-nanosheets and their successful application to remove toxic metals from water matrices.