Fixed-bed reactor scale-up and modelling for Cr(VI) removal using nano iron-based coated biomass as packing material

Uncoated and nano iron-based coated biomass were employed as packing material in lab-scale and large-lab-scale columns for the removal of Cr(VI) from synthetic wastewaters. A remarkable Cr(VI) removal efficiency (up to about 65%) was observed in large-lab-scale configuration, thus allowing to treat notable amounts of effluents volumes (30–70 L, basing on the inlet flow-rate) at fixed bed height of 38 cm and a sorbent mass of 850 g and 790 g of uncoated and coated material, respectively. The data obtained from lab-scale experiments at fixed bed height and three different inlet flow-rates were used in a non-linear regression procedure in the gPROMS environment to estimate sorption and kinetic parameters of three developed dynamic models. The regressed parameter values, film mass transfer coefficient kf, sorption kinetic constant Ka and reaction kinetic constant k, were then used as input values for the developed model to model the experimental data obtained at large-lab-scale. The modelling results demonstrated the suitability of the film-diffusion based model to well fit the lab-scale data and to model the large-lab-scale breakthrough curves of Cr(VI) removal using both uncoated and coated biomass. For this reason, and also considering the laminar flow conditions, this mass transfer mechanism was considered the limiting step of the Cr(VI) removal process.