Removal of copper ions from wastewater via adsorption on modified hematite (α-Fe2O3) iron oxide coated sand

Abstract

In this study, we improved the surface quality of synthetic hematite (α-Fe2O3) iron oxide coated sand (HIOCS) and its adsorption and desorption capabilities for copper ions in aqueous solutions, and we evaluated the iron oxide content on the sand surface. We prepared three different control pH (1, 5, and 10) solutions using FeCl3, to obtain the above results. In addition, we used X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and EDX, analyses were performed for characterization of analysis to characterize the surface morphologies of the coated layer and observe copper ion adsorption on the coated sand surfaces. Batch experiments were conducted to assess copper ion adsorption under specific parameters, such as the influence of time, dosage, pH, and initial copper concentration. Adsorption isotherms and kinetics models were used to fit the experimental data at various temperatures (287, 297, and 307 K), and different desorption media were studied to assess copper ion regeneration from hematite (α-Fe2O3) iron oxide coated sand (HIOCS). We observed high intensity, pure hematite (α-Fe2O3) crystal peaks, and iron content (105.3 mg/g) on the sand coated at a pH of 1, and copper ion removal efficiency was more effective (94%) at lower pH, compared to the sand coated at a pH 5 and 10 (81% and 84%, respectively) at constant parameters (pH of 6, dose of 4 g/L, temperature of 297 K, 30 mg/L of Cu2+ concentration, and contact time of 180 min). The Langmuir isotherms model (R2 = 0.991) and pseudo-second-order kinetic models (R2 = 0.978) were found to correlate better than the Freundlich isotherm model (R2 = 0.966), or the pseudo-first-order kinetics model (R2 = 0.965). We achieved the highest Cu2+ adsorption of qm = 3.93 mg/g, as obtained from the Langmuir isotherms. We also observed that acidic (HCl and H2SO4) solutions were the best desorption media for copper ions on the surface of hematite (α-Fe2O3) iron oxide coated sand (HIOCS). Thus, this study found that copper ions can be removed through an environmentally friendly process using low-cost hematite (α-Fe2O3) iron oxide coated sand (HIOCS), under suitable conditions.