Enhanced simultaneous removal of direct red 81 and bisphenol A from aqueous media by coupling nano zero-valent iron (nZVI) particles with graphene oxide and copper: Isotherm and kinetic adsorption studies

Abstract

In this study, nanoscale zero-valent iron (nZVI) coupled with graphene oxide (GO) and copper (Cu) was synthesized and evaluated to develop an efficient adsorbent for the simultaneous removal of Direct Red 81 (DR 81) and bisphenol A (BPA) from aqueous environments. The adsorbent was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and vibrating sample magnetometer (VSM). The particle size distribution (PSD) findings demonstrated that the average size of nZVI-GO-Cu was equal to 20.89 nm. The maximum removal efficiency (97.50%) was obtained at optimized conditions, including pH of 5, the adsorbent dosage of 0.5 g, contact time of 35 min, and initial concentration of 5 mg L−1. The experimental data were investigated using the Langmuir and Freundlich isotherm models. The Langmuir model was revealed to be a better model (R2 = 0.9993), and the adsorption of DR 81 was found to be most desirable on nZVI-GO-Cu with a maximum adsorption capacity (qmax) of 21.32 mg g−1. Also, the adsorption kinetics models were assessed and the resulting data fitted well with a pseudo-second-order (PSO) kinetic model with R2 equal to 0.9991. All in all, the present results indicate that this environmentally friendly, efficient, and inexpensive adsorbent can be useful for the simultaneous elimination of DR 81 and BPA from aqueous media.