Synthesis of Gallus gallus domesticus eggshells and magnetite bio-composite for Cr(VI) removal: adsorption kinetics, equilibrium isotherms and thermodynamics.

This research study aimed to remove chromium (Cr⁶⁺) from aqueous and industrial effluent by natural Gallus gallus domesticus eggshell waste magnetized with Fe₃O₄ nanoparticles (MES). A literature survey showed that the sorption of Cr on the modified magnetite form of this biomass had not been explored before. Structure, morphology, functional groups, and thermal stability of the prepared modified biosorbent were characterized by scanning electron microscopy, X-ray diffraction pattern, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results of the characterization study confirmed the suitability of Cr adsorption on the proposed adsorbent. The optimization studies were performed to measure the suitable conditions for the adsorption process. The most suitable pH for maximum chromium adsorption by MES was 2. The contact time for maximum adsorption was noted to be 30 min, and the most suitable temperature was found to be 20°C. It was observed that MES showed 95% removal of Cr. The kinetics data for MES followed the pseudo-first-order kinetic model, while the intraparticle diffusion played a significant part in the rate-controlling step. The results described the pseudo-first-order kinetic model for Cr adsorption by MES, with the highest value of correlation coefficient R² = 0.864. The equilibrium for adsorption data was best described by Langmuir isotherm. For the thermodynamic process, ΔG°, ΔH°, and ΔS° were calculated, the value of ΔH and ΔS was –34.622 and –0.11 kJ/mol K, respectively, and found that adsorption of Cr was spontaneous and exothermic. The suitability of MES in industrial effluent was also carried out that offers a green, sustainable, cost-effective, and real-world water treatment solution for water purification having Cr from wastewater/industrial effluent. [ABSTRACT FROM AUTHOR]