Processing and characterization of magnetic composites of activated carbon, fly ash, and beach sand as adsorbents for Cr(VI) removal

Abstract

The objective of this study is to prepare magnetic composites as adsorbents for Cr(VI) from wastewater. The prepared composites are magnetic activated carbon (M-AC), magnetic ash (M-ASH), and magnetic sand (M-SAND). These composites were characterized using XRF, FTIR, XRD, and TGA, and then tested as adsorbents for toxic Cr(VI) ions from synthetic wastewater. The elemental analysis of the composites showed a crucial increment in the Fe content of about 6425%, 3600%, and 93% for M-SAND, M-AC, and M-Ash, respectively. Their FTIR spectrum showed the existence of the Fe–O bond vibration, indicating the presence of Fe3O4 particles as confirmed by the XRD pattern. The pseudo-second-order model best described the adsorption kinetic results and the Redlich-Peterson isotherm model accurately described the equilibrium data of ion adsorption by the three composites at 25 and 40 °C with relatively high values of R2. The composites showed their highest adsorption capacities for Cr(VI) ions at 40 °C with an average adsorption capacity of the composites was about 50 mg/g. These relatively high values demonstrate the adsorption ability of the magnetic composites and present a strategy to use the adsorption process for Cr(VI) ions by these composites as efficient adsorbents.

Keywords

• Magnetic composites
• Particles characterization
• Cr(VI) adsorption
• Adsorption isotherm
• Adsorption kinetics
• Adsorption thermodynamics