Biomass Templated Fabrication of Hierarchical Hollow Cotton Cellulose/Layered Double Oxide Adsorbent for Efficient Cd ²⁺ Adsorption

With the rapid progression of industrialization, cadmium contamination in aquatic environments had become a major global concern due to its high toxicity, strong bioaccumulation, and environmental persistence. Layered double oxide (LDO) has drawn considerable attention for cadmium removal from water owing to the large surface area and abundant adsorption sites. However, conventional LDO materials often suffer from severe layer stacking and particle agglomeration, which restrict the exposure of active sites and hinder the adsorption capability. To overcome the drawbacks, a cotton fiber/MgAl-layered double oxide (C/LDO) adsorbent with a three-dimensional (3D) hollow structure was fabricated through a biomass template-assisted sacrificial strategy. Inspired by natural cellulose fibers, LDO nanosheets were directionally grown on the surface of alumina fibers derived from cotton, generating a hierarchical porous structure with a high specific surface area and improved accessibility of adsorption sites. The C/LDO demonstrated outstanding Cd²⁺ adsorption performance, with a maximum capacity of 237.10 mg/g at 25 °C. Mechanistic investigations indicated that Cd²⁺ adsorption was facilitated by a synergistic effect of coordination and mesopore enrichment. This study not only elucidates the underlying mechanisms of cadmium adsorption but also proposes a design strategy for developing efficient adsorbents, offering significant potential for water remediation applications.