Anchoring Silver Ions onto Cysteine-Derivatized Cellulose and Its Antibacterial Effect

Adsorption of silver ions onto natural biopolymers like cellulose offers dual benefits: (i) recovery of precious metals from waste and (ii) application as antibacterial agents, including water treatment. In this work, cellulose is derivatized with a thiol-containing amino acid, cysteine, via two approaches to enhance silver anchoring by exploiting the high affinity between thiol groups and soft metals. The first method involves direct esterification to produce Cel-Cys-Est, while the second uses periodate oxidation to form dialdehyde cellulose (DAC), followed by linking with cysteine via a Schiff base reaction, creating DAC-Cys. After confirming the successful cysteine derivatization using X-ray photoelectron spectroscopy (XPS), the adsorption characteristics towards silver ions have been optimized for parameters like pH, adsorbent dosage, and ion concentration. The kinetic studies have shown the pseudo-second-order model for silver ion adsorption over both materials, while the isotherm studies have indicated Langmuir-type monolayer adsorption. The silver-loaded DAC-Cys, having higher adsorption capacity, has demonstrated significant antibacterial activity against Escherichia coli and Staphylococcus aureus. This work highlights the versatility of cysteine-derivatized cellulose as an effective, eco-friendly material for silver ion sequestration and its promising application in antimicrobial domains.