Hierarchical mesoporous Cys-PDA@CoNi-LDH for efficient Cu2+ removal: Synergistic mechanism of coordination and spatial confinement

The thorough removal of Cu 2+ from water poses a formidable challenge in environmental remediation. To overcome the performance limitations of traditional adsorbents that rely on physical pores or single functional groups. This study successfully constructs a hierarchical mesoporous composite, denoted as Cys-PDA@CoNi-LDH (where Cys, PDA, and LDH refer to L -cysteine, polydopamine, and layered double hydroxide, respectively). It is synthesized by grafting Cys onto a PDA framework via Michael addition, followed by in situ growth of CoNi-LDH nanosheets. The composite exhibits a high Cu 2+ adsorption capacity of 295.3 mg·g −1 and a removal efficiency of 92.2 % under optimal conditions (318 K, pH=6), with strong resistance to ionic interference. The synergistic mechanism involves specific -SH coordination, LDH ion exchange, surface complexation, and mesoporous confinement. Efficient desorption (86 % recovery) is achieved using 0.1 mol·L −1 HCl, and over 75 % of the initial capacity is retained after five cycles. Fixed-bed column experiments confirm its practical potential, with breakthrough curves well-fitted by Thomas and Yoon-Nelson models (adjusted R 2 = 0.986–0.999). Notably, it achieves a treatment capacity of 1.7 L·g −1 for low-concentration Cu 2+ (5 mg·L −1 ). This work provides a promising strategy for designing selective and renewable adsorbents for water purification.