Strengthened arsenic adsorption over Ni-modified γ-Al2O3 under different operation conditions: An experimental and simulation study

Abstract

• Enhanced electron transfer among Al 2 O 3 , NiO and As 2 O 3 boosts adsorption performance. • NiO reduces TS energy barrier of physically adsorbed As 2 O 3 into chemisorption state. • Stronger attraction forces promote desorption temperatures of Ni-modified γ-Al 2 O 3 . • Bond stretch of Ni-O helps to capture more As 2 O 3 molecules at higher temperatures. • Experiments of arsenic adsorption are consistent with DFT/MD simulation results. Variations of operation conditions have negative effects on arsenic adsorption of γ-Al 2 O 3 . Therefore, it is necessary to modulate γ-Al 2 O 3 for better arsenic adsorption performances under complex industrial conditions. In this study, besides complete experiments used to characterize arsenic adsorption features of Ni-modified γ-Al 2 O 3 , density functional theory (DFT) calculations and molecular dynamics (MD) simulations are also wielded to investigate arsenic adsorption enhancement mechanisms in microscale and mesoscale, respectively. As to DFT calculations, it is revealed that the strengthened electron transfer between As 2 O 3 and the adsorbent is the principal factor for 24.59–63.14 % higher adsorption energies. What is more, transition state (TS) energy barriers of physisorption structures being transformed into chemisorption are curtailed by 24.93–54.23 % and negative effects of high temperatures on dissociation of adsorption structures are also partially impaired. As far as MD simulations are concerned, stronger attraction forces of the adsorbent to arsenic molecules and the As 2 O 3 aggregation effect are leading factors for capturing 26.75 % more As 2 O 3 , which counters adverse effects of variable operation conditions. Regarding experiments, it is manifest that the arsenic adsorption amounts over Ni-modified γ-Al 2 O 3 are averagely 24.28–32.55 % higher than those over pure γ-Al 2 O 3 , which is consistent with DFT and MD results. Analyses of above three aspects would provide significant information for Ni-modified γ-Al 2 O 3 being used in real industries to remove arsenic from flue gas.