Malachite green adsorption from aqueous medium by chitosan assisted silver nanoparticles (AgNPs): Isotherm and thermodynamics studies

The contamination of water by toxic, non-biodegradable dyes like malachite green (MG) presents serious environmental and health risks, demanding effective and sustainable removal strategies. This study explores the adsorption of MG from aqueous solutions using silver nanoparticles (AgNPs) as adsorbents. The synthesized AgNPs were characterized using FTIR, XRD, UV-Visible spectrophotometry, and SEM. XRD confirmed a face-centered cubic crystalline structure, while SEM images showed both spherical and irregular granular shapes. FTIR spectra displayed peaks between 1005 and 1646 cm⁻¹, indicating phosphonate bond formation between –NH₃⁺ groups of chitosan and –PO₃²⁻ moieties of sodium tripolyphosphate (NaTPP) during cross-linking. Adsorption experiments revealed that all tested factors significantly affected MG uptake by the AgNPs, demonstrating their potential for effective dye removal from aqueous environments. AgNPs effectively remove MG in acidic conditions of pH of 4.7, contact time of 80 min, and temperature of 45 °C, indicating that electrostatic interactions primarily drive. The adsorption models were best described by Tempkin isotherms. The findings suggest that AgNPs are promising adsorbents for MG removal from aqueous environments. KEY WORDS: Malachite green (MG), Silver nanoparticles (AgNPs), Sodium tripolyphosphate, Adsorption, Cross-linking, Electrostatics attraction Bull. Chem. Soc. Ethiop. 2025, 39(7), 1283-1299. DOI: https://dx.doi.org/10.4314/bcse.v39i7.5