Unexpected ultrafast and high adsorption capacity of oxygen vacancy-rich WOx/C nanowire networks for aqueous Pb2+ and methylene blue removal

Abstract

The development of advanced adsorbents with high adsorption capacity and fast adsorption rates is one of the most important issues for water treatment. Herein, oxygen vacancy-rich WO_x/C inorganic–organic hybrid nanowire networks were prepared by a one-pot and high yield solvothermal method. With their unique intercrossed hierarchical structure and abundant active sites, the WO_x/C networks exhibited high adsorption capacities of ∼1224.7 and 1188.3 mg g⁻¹ for the removal of Pb²⁺ and MB, respectively. Moreover, the adsorption equilibriums of Pb²⁺ and MB onto WO_x/C networks can be achieved within only ∼1 min, which were among the fastest of those previously reported for Pb²⁺ and MB adsorbents. These unexpected ultrafast and high adsorption capacities are attributed not only to the unique network nanostructure, but also to the enriched oxygen vacancies onto which small carbonaceous molecules can attach with high affinities, which may serve as anchoring sites for Pb²⁺ ions or dyes. The removal mechanism of Pb²⁺ and MB on WO_x/C can be attributed to ion exchange, π–π interaction, hydrogen bonding and/or electrostatic attraction. This study not only provides a new strategy to design inorganic–organic hybrid adsorbents, but also demonstrates its prospective application in adsorptive removal and/or recovery of heavy metals and organic pollutants on a large scale.