Abstract
Hexavalent Chromium species are classified as hazardous compounds due to their high toxic potential, considering also their remarkable solubility and redox potential. Various processes have been developed to remove/recover Cr(VI) species from polluted groundwater, such as membrane processes, ion-exchange and adsorption and chemical or biochemical reduction. Indeed, the reduction/removal process of Cr(VI) through iron-based materials usually leads to a pH increase of the reaction medium, allowing to facilitate the subsequent precipitation of the Cr(III) species. In this context, the use of iron based nano-particles (IBNs) supported on bio-polymer matrix allowed to maximize the Cr(VI) removal capacities of iron-based materials, leading to the production of high active and eco-compatible nano-materials. The use of chitosan as surface-modified agent, allows the reduction of aggregation forces among the produced IBNs, leading to higher surface active areas and chemical reactivity. At the same time, the use of a bio-polymer increases the eco-compatibility of the IBNs, reducing the possible interaction with bacteria and microorganisms during the treatment process. In this work chitosan-nanomagnetite particles were synthetized and employed as packing material inside fixed-bed lab-scale column (height 25 cm and diameter of 1.5 cm) to remove, in continuous, Cr(VI) species from synthetic wastewaters. The tests were performed at different inlet flow-rate values (2, 5 and 7 mL/min) at fixed Cr(VI) initial concentration (20 mg/L) and varying the solution pH (pH=4 and 7). The obtained breakthrough curves were then modeled according to the classical dynamic Thomas model.
