Efficient removal of methylene blue and lead( <scp>II</scp> ) using a magnetic <scp>C</scp> u‐ferrite bio‐nanocomposite from black seed ( <i>Nigella sativa</i> <scp>L</scp> .) waste: Synthesis, characterization, and adsorption study

Abstract It is economically important to convert industrial biowastes into low‐cost and environmentally friendly valuable materials without harming the environment, and to use them in water treatment. Herein, to evaluate the black seed ( Nigella sativa L.) industrial processing waste, it was converted into a new magnetically separable copper ferrite carbonaceous (CuF@BAC) nanocomposite material. It was characterized with VSM, BET, SEM–EDX, XRD, Raman, FT‐IR, Boehm titration, and pH ZPC techniques. Its BET surface area, total pore volume, average pore diameter, mesopore contribution, and saturation magnetization are 455 m 2 /g, 0.280 cm 3 /g, 2.5 nm, 64.5%, and 15.01 emu/g, respectively. Its ability to remove methylene blue (MB) and lead (Pb(II)) from water was tested. Kinetic and equilibrium isotherm data were modeled to describe the studied adsorption systems. The maximum removed quantities for MB and Pb(II) are 625 mg/g and 345 mg/g, respectively. The Δ G o , Δ H o , and Δ S o parameters computed to define the thermodynamic behavior of each adsorption system indicated that the processes were spontaneous, endothermic for MB and exothermic for Pb(II). Regeneration studies performed with HCl for each adsorbate showed it had reusable stability at high adsorption efficiency for up to four cycles. This study revealed that CuF@BAC is a promising green adsorbent due to its high adsorption efficiency, easy magnetic separation, and reusable properties.