Magnetic biocomposite based on peanut husk for adsorption of hexavalent chromium, Congo red and phosphate from solution: Characterization, kinetics, equilibrium, mechanism and antibacterial studies

Abstract

A biocomposite (PN–Fe3O4-PEI) was synthesized via the chemical modification of peanut husk (a low-cost adsorbent) with Fe3O4 particles and polyethyleneimine under benign environmental conditions. The modification agents used in this study were observed to overcome the challenges associated with the use pristine peanut husk with a concomitant enhancement in its efficiency as an adsorbent. Results from the characterization studies employed in this study confirmed PN-Fe3O4-PEI to be a crystalline magnetic adsorbent with a mesoporous structure. The adsorption property of the developed material (PN–Fe3O4-PEI) for wastewater treatment was investigated using Chromium (VI), Phosphates (PO43−) and Congo red (CR) as model pollutants. Using the batch method, PN-Fe3O4-PEI exhibited a maximum monolayer adsorption capacity of 58.4, 13.5 and 71.3 mg g−1 for Cr(VI), PO43− (as P g L−1) and CR, respectively and was dependent on temperature and initial adsorbate concentration. Kinetic studies revealed that the Elovich equation, the pseudo-second order kinetic model and double constant equation well described the uptake of Cr(VI), PO43− and CR onto PN-Fe3O4-PEI, respectively. These results may confirm the uptake of these pollutants to be mainly driven by chemical forces. In addition, PN-Fe3O4-PEI was observed to be efficient for the decontamination of the studied pollutants in real water samples as well as exhibit antibacterial properties towards the growth of S. aureus. These properties of PN-Fe3O4-PEI with its other excellent features such as high stability in solution, good regeneration properties and its facile retrieval from the solution using a magnet promote its suitability for practical wastewater treatment.