Rose-inspired salt-responsive hierarchical microbead via in-situ growth of layered double hydroxide plates onto rosin-derived resin for efficient tetracycline removal: Ingenious design, advanced molecular simulations, and rethinking adsorption mass transfer

Abstract

Flower-like Ni/Al layered double hydroxides (Ni/Al-LDHs) were in-situ grown on rosin-derived resin to design a rose-inspired hierarchical microbead (RIHMB), which is efficient in removing tetracycline hydrochloride (TCH) from water system. The ingeniously designed dual-layer structure of RIHMB features an inner layer rich in quaternary ammonium (–R₄N⁺) that strongly attracts negatively charged TCH, and a rose-like outer layer with numerous pores to accommodate the adsorbates. RIHMB exhibits exceptional reusability, achieving over 92% TCH removal efficiency after five cycles. Molecular dynamics simulations demonstrate that RIHMB not only adsorbs TCH with high efficiency but also facilitates its remarkably rapid release (NaCl as desorbent). This outcome is attributed to the porous structure of Ni/Al-LDHs, which traps TCH and acts as a physical barrier, preventing direct interaction with –R₄N⁺. Then, chloride ions in the desorbent neutralize the positive charge of RIHMB, reduces its adsorption affinity for TCH, and promotes rapid desorption. A novel Wen Li-Wei Wei adsorption mass transfer model is presented, which reveals the collective influence of liquid-film diffusion, pore mass transfer, and sorption onto active sites on adsorption mass transfer, providing valuable insights into the underlying mechanisms. Multiple quantum chemical theoretical calculations were integrated to quantify the contributions of charge interaction, hydrogen bonding, π-π interaction, and van der Waals force to adsorption. A scale-up experiment conducted on a real water system offers a promising strategy for the remediation of environments contaminated with antibiotics.