Rice husk biochar doped with deep eutectic solvent and Fe3O4/ZnO nanoparticles for heavy metal and diclofenac removal from water

In this study, ternary recyclable rice husk biochar doped with deep eutectic solvent and Fe3O4/ZnO nanoparticles (Fe3O4-ZnO/RBC-DES) was successfully synthesized and used for the removal of Cr(VI), Pb(II), and diclofenac sodium from aqueous solution. The characterization results of several techniques, naming XRD, FTIR, SEM-EDS, TGA, TEM, and surface area analysis, confirmed that the modified nanosorbent surface offered more active adsorption sites, facilitating the Cr(VI), Pb(II), and diclofenac sodium adsorption. Introducing metal oxide nanocomposite (Fe3O4-ZnO) effectively leads to superior kinetic removal efficiency. At equilibrium conditions, mesoporous FZRBC-DES15 shows maximum adsorption capacity (Qmax) of 66.23, 384.62, and 24.33 mg/g for Cr(VI), Pb(II), and DCF, respectively. The adsorption kinetics fit the pseudo-second-order model. The adsorption behavior coincided with homogeneous adsorption materials as reflected by well-fitting the Langmuir model for Cr(VI) and Pb(II) and the heterogenous mechanism for DCF as fit with the Freundlich model. The synthesized adsorbent is an excellent adsorbent that removes selected heavy metal ions and diclofenac sodium from aqueous solutions. It is used in waste resource utilization as it is easily recycled.