Large-scale production of 4MoO3·2NH3·H2O nanosheets through antisolvent crystallization for highly efficient removal of cationic dyes

Abstract

This article describes a practical approach for the rational design and large-scale production of different morphologies and sizes of 4MoO 3 ·2NH 3 H 2 O (MAH) nanosheets. The optimized MAH-20 shows the best adsorption capacities for various cationic dyes such as methylene blue (1169.2 mg·g −1 ) and rhodamine B (1452.8 mg·g −1 ), benefiting from its high Mo 5+ centres concentration, negative surface charge, small nanosheet thickness, and high surface-to-volume ratio. We reveal that the adsorption behaviour of MAH-20 is mainly driven by electrostatic interactions, while also affirming the existence of coordination interactions between surface coordination-unsaturated Mo and dye molecules. • Large-scale preparation of 4MoO 3 ·2NH 3 ·H 2 O (MAH) nanocrystal was realized. • The MAH-x nanosheets showed selective adsorption capacity for cationic dyes. • High adsorption capacity was realized because of the existence of Mo 5+ centers. • MAH-20 membrane remained highly durability in reuse experiments. A facile method for the large-scale production of 4MoO 3 ·2NH 3 ·H 2 O (MAH) nanocrystal with tunable size and morphology is developed through an antisolvent crystallization approach. The introduction of hydroxyl groups during crystallization promotes the formation of oxygen vacancies on the MAH. Due to the high concentration of Mo 5+ centres, small nanosheet thickness, and sandwich-like crystal structure, MAH-20 exhibits an outstanding adsorption capability toward cationic dyes, with the maximum adsorption capacities up to 1169.2 mg·g −1 for methylene blue (MB) and 1452.8 mg·g −1 for rhodamine B (RhB), which are almost 10 times as that of MAH-0. An electrostatic adsorption mechanism is proposed to interpret the highly selective adsorption activity toward cationic dyes. Moreover, a fast and recyclable treatment and adsorbent regeneration are realized based on a continuous flow filtration device.