Development of a magnetite functionalized cow horn pumice biocomposite for hexavalent chromium removal

Abstract A magnetite-functionalized cow horn/pumice (Fe 3 O 4 –CH/P) biocomposite was synthesized via in situ co-precipitation and evaluated for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. A multifunctional adsorbent was engineered by integrating keratin-rich cow horn with highly porous pumice and incorporating magnetite, thereby enhancing its physicochemical properties and enabling efficient magnetic separation. To fully characterize the magnetite-functionalized biocomposite, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were all employed. At optimized adsorption conditions (pH 3, contact time 120 min, 2 g per100 mL solution (20 g·L − 1 ) dosage), batch adsorption tests showed a very high removal efficiency (> 99.8%). This demonstrates the material’s high affinity for oxyanion species of Cr(VI). The adsorption data are well predicted by the pseudo-second-order kinetic model (R 2 = 0.99926), indicating that surface-mediated interactions are crucial to the adsorption process. It was determined through isotherm analysis that the Langmuir model provided a better fit (R 2 = 0.9994, a maximum capacity of 15.34 mg·g − 1 ), indicating that homogeneous active sites with a maximum capacity of 15.34 mg·g − 1 and monolayer adsorption are the dominant mechanism. The adsorption process is regulated by electrostatic attraction, surface complexation, and potential redox interactions. According to the results, the magnetite-functionalized cow horn/pumice (Fe 3 O 4 –CH/P) bio-composite is environmentally friendly and a highly effective adsorbent for treating water contaminated with chromium.