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On the removal of hexavalent chromium by olive stones coated by iron-based nanoparticles: Equilibrium study and chromium recovery
- Vilardi, Giorgio, Ochando-Pulido, Javier Miguel, Verdone, Nicola, Stoller, Marco, Di Palma, Luca
- Journal of cleaner production 2018 v.190 pp. 200-210
- adsorption, aqueous solutions, biomass, chromium, iron, magnetite, nanoparticles, olives, pH, seeds, solvents, sonication, washing
- In this work hexavalent chromium, Cr(VI), removal in aqueous solution by olive stones coated by zero-valent iron and magnetite nanoparticles was investigated. The Cr(VI) removal test results showed that the coated biomass adsorption capacity significantly increased (2.54 and 4.11 mg Cr g−1) when compared to the uncoated one (1.48 mg Cr g−1). Optimal removal conditions were reached by fixing the operating parameter values for pH, mass concentration and contact time equal to 3, 2.5 g L−1 and 120 min for the uncoated and equal to 2, 1.5 g L−1 and 120 min for the coated biomasses, respectively. Both Cr(VI) and Cr(III) recovery, after 5 cycles of use, was investigated using different solvents and operative conditions (with and without sonication), showing that remarkable Cr recovery was possible using the more environmentally friendly washing procedure. A possible Cr(VI) removal mechanism will be here proposed and discussed, considering both reduction and adsorption contribution towards Cr(VI) removal in aqueous medium and capable to justify the obtained results.