Experimental and simulation results of the adsorption of Mo and V onto ferrihydrite

Abstract

This study aims to highlight discrepancies between experimental and simulation linked to the mechanisms of Mo and V adsorption onto ferrihydrite (FHY) nanoparticles. We have measured adsorption capacities and uptake efficiencies and then fitted and compared these with outputs from various geochemical and adsorption models that were run as a function of pH, surface area (SA) and ferrihydrite particles size distributions. Our results revealed that the experimental data for the Mo system could be fitted very well, but this was not the case for the V system, when a model default value for the SA of FHY of 600 m2 g−1 was used. The discrepancy in the results for the V system can be explained by the lack of specific V species and/or associated constants in databases and variation in software versions, which change the outputted chemical species. Our comparative results also confirm that any experimental variables used as modelling inputs need to be checked carefully prior to any modelling exercises.

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

“…It's oen used in the removal and stabilization (under ideal selective conditions) of a range of toxic elements in natural and man-made environments through adsorption and co-precipitation. 1,2,[9][10][11][12] The biotic reduction of iron(III) oxy-hydroxides such as 2-line FH by Fe-reducing bacteria plays an important role as an electron shuttle in various redox processes that control the biogeochemical cycling of transition and metalloid elements (e.g. Fe, As, Se, U, Mn) as well as organic matter/nutrients (e.g.…”

Surface Coverage Simulation and 3D Plotting of Main Process Parameters for Molybdenum and Vanadium Adsorption onto Ferrihydrite

“…The maximum concentration of anions was selected to be below the anion saturation in solution. According to our previous solution chemistry modelling results (see SI of Brinza et al, 2019 [ 6 ]), no molybdenum and vanadium polymerization or precipitation phases were expected to occur at chosen anions concentration. The lack of Mmolybdenum and vanadium precipitated or polymerized phases at ferrihydrite surface were also proved by our previous XAS results [ 6 ].…”

“…Batch experiments were conducted in 500 mL glass beakers, under N 2 atmosphere, using 100 µmol L −1 molybdenum and vanadium solution and 0.1 g L −1 ferrihydrite. Further details are to be found in previous works [ 5 , 6 ]. A pH adsorption edge diagram as well as their kinetic profile plotting and modelling were treated in our previous work [ 6 ].…”

“…Further details are to be found in previous works [ 5 , 6 ]. A pH adsorption edge diagram as well as their kinetic profile plotting and modelling were treated in our previous work [ 6 ]. Here, quantitative values at equilibrium were only taken for the 3D plotting of main adsorption parameters and to derive information about their interrelations.…”

“…Of the anions that may constitute pollutants if their concentration in surface waters exceeds the limits imposed by environmental standards [ 3 , 4 ], the interactions between molybdenum (Mo) and vanadium (V) and ferrihydrite have so far been little studied [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Besides our previous studies [ 5 , 6 , 12 ], which present high resolution qualitative and quantitative experimental investigations of molybdenum and vanadium interactions with ferrihydrite, the literature contains mostly modelling/computational studies that can be used to simulate the transport and bioavailability of these anions in the environment [ 7 , 9 , 10 , 13 ]. From our experimental vs. modelling experience, we have shown that some discrepancies may exist between the two approaches.…”