Valorization of coconut water-derived bacterial cellulose in water treatment: environmentally benign modification to enhance the adsorption capacity for multiple heavy metal ions

Abstract

Bacterial cellulose, produced through the fermentation of sugar-rich natural resources, exhibits a unique three-dimensional structure and higher purity than plant-derived cellulose, making it promising for various applications. In this study, we modified bacterial cellulose from coconut water using readily available reagents, such as diammonium hydrogen phosphate and urea, without toxic solvents. Characterization techniques, including XPS, SEM-EDX, XRD, FTIR, TGA, and elemental analysis, confirmed successful phosphorylation with a phosphorus substitution degree of up to 11%. We investigated the effects of phosphorylation and adsorption conditions on the uptake of four metal ions (Cu²⁺, Cd²⁺, Fe³⁺, and Pb²⁺), finding a correlation with phosphorylation efficiency. The adsorption data conformed to the Langmuir model, indicating monolayer adsorption, and kinetic studies suggested that chemisorption should be the dominant mechanism. The study expanded to five additional metal cations, including Ni²⁺, Cr³⁺, Zn²⁺, Co²⁺, and Mn²⁺, demonstrating enhanced adsorption capacity due to the phosphorylation. The single-metal uptake ranged from 77.5 to 113.9 mg g⁻¹, exhibiting a 2.3–4.4-fold improvement over unmodified bacterial cellulose. Similar results were obtained for simulated wastewater samples containing all these metal ions. Importantly, the bacterial cellulose-based adsorbent was successfully recovered and reused for four cycles, maintaining considerable capacities. These findings highlight bacterial cellulose as a sustainable, high-quality alternative for water treatment and demonstrate its potential as a value-added functional material derived from sugar-based biomass.