Silver-rice husk cellulose composite for methyl orange adsorption: Kinetics, isotherm, and mechanism studies

Abstract

Biosorbents are alternative pollutant adsorbents, usually sourced from waste biomass and requiring little or no treatment, which are less expensive than conventional adsorbents. This study investigates the potential of silver-rice husk cellulose composite (AgNPs@RHC) using cashew apple juice (Anacardium occidentale L.) as a reducing agent silver for nanoparticles for the adsorption of methyl orange (MO). Characterization through SEM, FTIR, and XRD analysis showed a coarse surface, detected chemical functional groups, and the metallic Ag dispersed into cellulose fibers. The composite has pHpzc = 4.87 and was tested for MO removal via various pH levels, doses, contact times, and initial concentrations. The highest removal efficiency is observed at pH = 4, and it reaches 60 min before declining, indicating a saturation of active sites on the biosorbent surface. Isotherm study data fitted the Langmuir model with an affinity of KL indicating a monolayer adsorption process. The kinetic analysis performed on the study data favored the pseudo-second-order model. Overall, AgNPs@RHC provides a low-cost, ecofriendly, and promising alternative for treating anionic dyes.