Synthesis, structural, magnetic property, and Cd(II) adsorption behavior of Ca-substituted MgFe2O4 nanomaterials in aqueous solutions

Abstract

In the present study, magnetic nanomaterials (Mg_1-xCa_xFe₂O₄, 0.0 ≤ x ≤ 0.8) were prepared via a simple sol-gel method. The samples were characterized using XRD, TEM, SEM, EDX, FTIR, BET, and VSM. The structural and magnetic properties of prepared nanomaterials (NMs) were investigated, and the adsorption capacity of Cd²⁺ from aqueous solution was evaluated via flame atomic absorption spectroscopy (AAS). The impact of several factors on Cd²⁺ adsorption such as contact time (1-60 min), pH (3-8), dose (0.003-0.03 g), and initial concentration of Cd²⁺ (5-60 mg L^-1) has been assessed. The adsorption capacity of Cd²⁺ for the prepared NMs followed the pseudo-second order. Several isotherm models were analyzed, and the Langmuir model was found to be the best fit for NMs. Among as-prepared NMs, Mg_0.8Ca_0.2Fe₂O₄ (MCF2, cubic 97%, orthorhombic 3%, q_e 100 mg g^-1) and Mg_0.2Ca_0.8Fe₂O₄ (MCF8, cubic 18%, orthorhombic 83%, q_e 90 mg g^-1) samples exhibited the highest adsorption performance at conditions, viz., contact time 20 min, pH 7, NM dosage 3 mg, and ions at a concentration 60 mg l^-1. Cd removal percentages were achieved 93 and 75 for MCF2 and MCF8, respectively. Overall, the prepared MCF2 and MCF8 NMs could be used as effective adsorbents to eliminate toxic Cd²⁺ from polluted aqueous solution.

Keywords: Adsorption capacity; Adsorption mechanism; Cd(II) ions; MgFe2O4 nanomaterials; Phase transformation.