Kaolin-nano scale zero-valent iron composite (K-nZVI): synthesis, characterization and application for heavy metal removal

Abstract

The present study explored the synthesis of Kaolin-nano scale zero-valent iron composite (K-nZVI) by using chemical reduction method. Sorption characteristics of the K-nZVI for the removal of Cu(II) ions was studied in batch conditions. The physical and chemical structure of the K-nZVI composite was characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-XRF), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller studies (BET). The effect of pH, the initial metal ion concentration, and contact time on adsorption of Cu(II) onto K-nZVI was investigated. The K-nZVI exhibited good sorption performances over the initial pH range from 2.5 to 6.5. The kinetics data was studied by applying two sorption kinetic models (Pseudo-first and Pseudo-second-order) equations. The pseudo-second-order model was relatively suitable for describing the adsorption process. The equilibrium adsorption data is well fitted to Langmuir adsorption models. The maximum adsorption capacities of K-nZVI sorbent as obtained from Langmuir adsorption isotherm is found to be 178–200 mg g−1 for Cu(II). Sorption isotherm models (Langmuir and Freundlich) were applied to the experimental data. The adsorption kinetics was well represented by the pseudo second order rate equation, and the adsorption isotherms were better fitted by the Langmuir equation. The thermodynamic studies showed that the adsorption reaction of Cu(II) is endothermic processes. TheK-nVZI having number of features including easy preparation, environmentally friendly nature, low-cost and good sorption performance enable K-nZVI application in industrial purpose specifically in the field of industrial water treatment.