Facile synthesis of high-efficiency magnetic graphitic carbon nitride adsorbents for the selective removal of hazardous anionic dyes in wastewater

Abstract

In this study, a kind of novel magnetic composite, PEI-Fe₃O₄/g-C₃N₄, was synthesized by simple physical impregnation and used as an adsorbent to remove the anionic dye Congo red (CR) in water. The structural properties of composites were studied using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Brunauer–Emmett–Teller (BET) measurements and zeta potential techniques. PEI-Fe₃O₄/g-C₃N₄ could selectively remove anionic dyes from aqueous solutions. The adsorption kinetics and isotherms were systematically studied, and the adsorption process is in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model. The thermodynamic results indicated that adsorption is a process of spontaneous heat entropy increase. CR-sorbed PEI-Fe₃O₄/g-C₃N₄ was successfully desorbed with a NaOH solution, and 0.05 M NaOH had the best desorption effect. Furthermore, PEI-Fe₃O₄/g-C₃N₄ exhibited excellent recyclability and reusability. The results of the adsorption mechanism study indicated that the excellent adsorption performance of PEI-Fe₃O₄/g-C₃N₄ was attributed to the favorable electrostatic interaction, hydrogen bonding and π–π interactions between the adsorbent and CR. In addition to its excellent adsorption properties, the prepared adsorbent showed satisfied adsorption performance in actual water samples. Predictably, the prepared adsorbent has a potential application value in the environmental field.