Advances in Functionalized Bacterial Cellulose Composites for Heavy Metal Adsorption: Mechanisms, Regeneration, and Scale-Up Prospects

Contamination of water with heavy metals remains a life-threatening global concern due to the persistence, toxicity, and bioaccumulation of metals such as Pb(II), Cd(II), Cu(II), and Hg(II). Conventional remediation technologies, including ion exchange, membrane filtration, and precipitation, offer limited scalability and often generate secondary waste. In contrast, bacterial cellulose (BC) and its composite derivatives have emerged as sustainable bioadsorbents with tunable surface chemistry, high porosity, and exceptional biocompatibility. Over the past decade, BC-based materials have achieved adsorption capacities up to 571 mg/g for Pb²⁺, 509 mg/g or Cu²⁺, and 382 mg/g for Cd²⁺, outperforming most traditional bioadsorbents. This review systematically analyses the structural design, surface functionalization, and mechanistic pathways governing metal ion capture by BC composites. Special emphasis is placed on correlating modification strategies (carboxymethylation, amination, and magnetic) with adsorption kinetics, thermodynamics, and regeneration efficiency. Compared to previous reviews, this work uniquely integrates quantitative analysis, multi-metal adsorption behaviour, and insights from real wastewater applications, highlighting critical gaps in scalability, durability, and regulatory readiness. Finally, we outline future research trajectories, including green synthesis optimization and integration with hybrid technologies (photocatalysis and electro-adsorption) to link the gap between performance of research laboratories and industrial deployment. By providing a mechanistically grounded and application-oriented perspective, this review positions BC composites as next-generation materials for sustainable heavy metal remediation.