Removal of p-nitrophenol from simulated sewage using MgCo-3D hydrotalcite nanospheres: capability and mechanism

Abstract

4-Nitrophenol (4-NP) is an organic pollutant found in the wastewater discharged from coking and petrochemical industries, and it is highly toxic, persistent, and bioaccumulative. 4-NP is difficult to degrade and causes serious damage to human health and the ecological environment. In this study, MgCo-3D hydrotalcite nanospheres were synthesized via the hot solvent method using ZIF-67 as a template for 4-NP removal from wastewater. The composition and structure of MgCo-3D hydrotalcite nanospheres were characterized via X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Energy Dispersive Spectroscopy (EDS), and BET analyses. The maximum adsorption capacity was 131.59 mg g⁻¹ under the optimized conditions (pH = 7, t = 298 K, C₀ = 50 mg L⁻¹, dose = 0.4 g L⁻¹). The adsorption obeyed the Langmuir, Redlich–Peterson and Sips models and pseudo-second-order kinetics, and the adsorption activation energy was 29.4 kJ mol⁻¹, indicating a monolayer physical adsorption phenomenon. The adsorption of 4-NP on the MgCo-3D hydrotalcite nanospheres mainly involved hydrogen bonding and electrostatic interactions. The nanospheres were regenerated using the hot-air purging method. After five adsorption–desorption cycles, the adsorption capacity reached 107.6 mg g⁻¹, indicating the good regeneration performance of the MgCo-3D hydrotalcite nanospheres.