Hematite decorated functional porous graphitic carbon nitride binary nanohybrid: Mechanistic insight into the formation and arsenic adsorption study

Abstract

Here, hydroxyl functionalized porous graphitic carbon nitride (gCN) decorated with hematite (α-Fe2O3) nanoparticles (NPs) (P-gCN-OH/α-Fe2O3) were synthesized by an eco-friendly hydrothermal and thermal polycondensation process. The physicochemical investigation and mechanistic approach signified that glucose is responsible for porosity formation and potassium (K) ions from KCl are responsible for breaking the periodic chemical structure of gCN; while a trace amount of H2O in melamine helps in introducing hydroxyl groups in the P-gCN matrix. Apart from this, α-Fe2O3 NPs were also successfully introduced into the P-gCN-OH. The synthesized P-gCN-OH/α-Fe2O3 binary nanohybrid shows enhanced adsorption performance towards both arsenite (As(III)) and arsenate (As(V)) ions due to their greater specific surface area (242.5 m2/g). About > 96% and > 98% of As(III) and As(V) were adsorbed with an adsorption capacity of 22.22 mg/g and 27.80 mg/g respectively. The proposed adsorption mechanism was supported by the combined results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that arsenic (As) adsorption onto the P-gCN-OH/α-Fe2O3 surface was due to electrostatic attraction, simultaneous As(III) oxidation & adsorption, and monodentate & bidentate complex formation.