Enhanced removal of polystyrene microplastics by three-dimensional flower-like layered double oxide: Behavior and mechanism insight

Microplastics (MPs) as emerging pollutants are becoming a global threat due to their potential environmental and human health risks. Conventional adsorbents used for MPs elimination tend to be unstable in acid or alkaline conditions, leading to inferior removal efficiency. Herein, a robust and efficient adsorbent, i.e., hierarchically structural ZnAl-layered double oxides (H-ZnAl-LDO), was elaborately developed via a one-step calcination strategy. This process created a flower-like porous structure supported by ZnAl2O4 spinel and ZnO. H-ZnAl-LDO exhibited an outstanding adsorption ability for polystyrene (PS, typical MPs) across a wide pH range (3-11), achieving a removal efficiency of 85-100 % and a maximum adsorption capacity of 91.17 mg/g. The intraparticle diffusion model combined with SEM analysis revealed that pore filling contributed to PS removal. Evidence from in FT-IR and XPS spectra and zeta potential substantiated the PS removal was dominated by electrostatic interaction, hydrogen bonding, and complexation. In addition, given the over 90 % PS removal efficiency from natural water, H-ZnAl-LDO demonstrated high potential in practical applications. This study provides a promising adsorbent for removing microplastics in both acidic and alkaline environments and broadens scope of applications for LDO.