Hierarchical Zn3(OH)2V2O7·2H2O microsphere adsorbents for highly-efficient removal of Pb2+

Developing new, high-efficiency and low-cost adsorbents is of significant importance for efficient removal of contaminants from wastewater. Herein, hierarchical nanowire-assembled Zn₃(OH)₂V₂O₇·2H₂O microspheres (ZVO Ms) are prepared by a facile L-threonine (L-Thr) assisted hydrothermal method and explored as nano-adsorbents for the removal of Pb²⁺ from simulated wastewater. A formation mechanism is proposed based on the morphological evolution. The optimal ZVO Ms demonstrate satisfactory adsorption performance for Pb²⁺ with a maximum adsorption capacity of 461.6 mg g⁻¹, and the removal efficiency is approximately three times higher than that of nanosheet-assembled ZVO Ms obtained in the absence of L-Thr. The adsorption isotherms and kinetics were well described by the Langmuir isotherm model and the pseudo-second-order model, respectively. The thermodynamic data indicate that Pb²⁺ adsorption is an endothermic and spontaneous chemical adsorption process. The adsorption mechanism is uncovered based on electrostatic attraction and ion exchange. The excellent adsorption performance may be attributed to unique hierarchical structures and higher surface areas, which accelerate the transport of reactant molecules and provide abundant active sites for adsorption of Pb²⁺. This work provides a reasonable strategy to prepare novel hierarchical micro/nanoarchitectures and the as-prepared ZVO adsorbent may be used as a candidate for the removal of Pb²⁺ contaminants in wastewater.