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.