Magnetic corn silk composite: a sustainable approach for efficient removal of hexavalent chromium from aqua

A sustainable preparation route for Magnetic Corn Silk Composite (M-CSC) was established by using Fe₃O₄ for the removal of Cr(VI) from an aqueous solution to make use of corn silk waste. The study of the prepared composite material was done by FT-IR, XRD, SEM-EDX mapping, zeta potential, BET and VSM methods. The saturation magnetization of M-CSC was verified with the measured value of 27.23 emu/g and the porous nature of the sample was confirmed with the measured value of BET surface area of 139.49 m 2 /g. The optimum pH for the adsorption process is 2, the optimum temperature is 30 °C, the optimum dose of the adsorbents is 0.5 g, and the optimum time of contact for the process is 120 min as shown in the batch adsorption experiments where the efficiency of adsorption of Cr (VI) has reached 98.89%. The Elovich model was the best fit kinetic model among the kinetic models investigated and the Temkin model was good fit to the equilibrium data (R 2 = 0.942). There can be several steps in the adsorption process, such as electrostatic interaction, surface functional group interaction, but the possible mechanisms have not been defined yet and should be verified by chromium speciation and mass-balance analysis. The M-CSC maintained a significant Cr(VI) removal capacity even after 5 adsorption–desorption cycles, but the efficiency of the process was seen to drop slightly after each cycle. In summary, M-CSC has good potential to be used as a sustainable and magnetically recoverable adsorbent to remove Cr (VI) from aqueous solutions.