3D Wood Microfilter for Fast and Efficient Removal of Heavy Metal Ions from Water

Adsorption is an effective method for the treatment of heavy metal ions in water; however, the existing adsorbents are complicated to prepare, and costly and difficult to recover. In this work, a 3D wood microfilter was prepared by modifying wood for the removal of heavy metal contaminants from water. First, a green deep eutectic solvent was used to remove lignin from beech wood. Then citric acid and l-cysteine were sequentially used to graft carboxyl and sulfhydryl groups (-SHs) on the surface of cellulose. Finally, a three-dimensional wood microfilter with an abundant porous structure and adsorption sites was formed. The adsorption kinetics and adsorption isotherms of heavy metal ions on the 3D wood microfilter were systematically investigated using Cu²⁺ and Cd²⁺ as model species. The results showed that the 3D wood microfilter had a fast adsorption rate and high saturation capacity for both Cu²⁺ and Cd²⁺. Based on the advantages of easy processing and multilayer assembly and stacking, a three-layer wood microfilter was designed to achieve high flux rate (1.53 × 10³ L m^-2 h^-1) and high efficiency (>98%) for the removal of heavy metal ions in water. The enhancement mechanism of the adsorption process of Cu²⁺ and Cd²⁺ by the 3D wood microfilter was investigated using SEM and EDS, FTIR, and XPS characterization. The simple synthesis method and high adsorption efficiency of this wood microfilter provide a new strategy for the preparation of cheap, efficient, and recyclable adsorbents for heavy metal ions in water.