Hybrid CaO@MgO@g-C3N4 nanostructure as a cost-effective sorbent for hazardous organic dyes activated by additives

A novel CaO@MgO@g-C3N4 hybrid sorbent was fabricated in methanol media using a simple ultrasonication process. X-ray diffraction confirms the formation of a ternary composite with morphology and a relatively high surface area of 72.94 m2/g. While Fourier transforms infrared and X-ray photoelectron spectroscopy reveals the formation of nanohybrid. The adsorption experiments show that removing malachite green (MG) and Congo red (CR) dyes from aqueous solutions by CaO@MgO@g-C3N4 is pH-dependent; the maximum capacities obtained at pH = 7. The kinetic of CR removal is best described by the Elovich model, while the adsorption of MG is best-fit by pseudo-second-order kinetics. The equilibrium data of CR dye removal obeys to Freundlich model, suggesting multi-layer adsorption. Langmuir and Dubinin-Radushkevich models provide reliable fit parameters for MG equilibrium data, implying chemical adsorption. High adsorption capacities for MG and CR dyes by CaO@MgO@g-C3N4 are achieved, reaching 1182 and 1791 mg/g. In addition to its potential for organic dye removal, the CaO@MgO@g-C3N4 nanopowder proves to be chemically stable even after three regeneration cycles.

Automated summary

A novel CaO@MgO@g-C3N4 hybrid sorbent with a high surface area was successfully fabricated using a simple ultrasonication process in methanol media. The adsorption experiments showed that the removal of malachite green (MG) and Congo red (CR) dyes by CaO@MgO@g-C3N4 is pH-dependent, with maximum capacities achieved at pH = 7. The CaO@MgO@g-C3N4 nanopowder exhibited high adsorption capacities for MG and CR dyes, reaching 1182 and 1791 mg/g, respectively.