Reduction and removal of As(V) in aqueous solution by biochar derived from nano zero-valent-iron (nZVI) and sewage sludge

Biochar prepared by co-pyrolysis of nano-zero-valent iron and sewage sludge (nZVISB) was used to remove As(V) from aqueous solution. When the initial pH was 2, the initial As(V) concentration was 20 mg L-1, the dose of nZVISB was 10 g L-1, the contact time was 24 h, and the adsorption temperature was 298K, the removal efficiency of As(V) was greater than 99%. The isothermal removal of As(V) followed the Freundlich model better, and the maximum adsorption capacity of As(V) was 60.61 mg g(-1). The removal process of As(V) could be better described by pseudo-second-order kinetic model, and the rate-controlling step should be liquid film diffusion and chemical reaction. Thermodynamic analysis indicated that the removal of As(V) was a spontaneous and endothermic process dominated by chemical adsorption. The characterizations of nZVISB before/after adsorption and the solution after adsorption suggested that the iron-containing substances (Fe-0, Fe2+, FeOOH) and organics in the nZVISB had a great effect on the removal of As(V), and the As was mainly immobilized on nZVISB by speciation of As-O-Fe. (C) 2021 Elsevier Ltd. All rights reserved.