Removal of Sunset Yellow by Methanol Modified Walnut Shell

The present research was aimed to analyze the possibility of a novel low-cost biosorbent, Methanol Modified Walnut Shell (MMWS), to improve its biosorption properties with respect to the removal of Sunset Yellow (SY) from aqueous solution, The influences of process parameters, such as pH, temperature, and initial concentration of SY on its adsorption capacity were investigated in a batch system. The equilibrium data were evaluated using the Langmuir and the Freundlich models and the latter could provide a better fit. The Langmuir maximum adsorption capacity of SY onto MMWS was 18.35 mg/g at 298 K, which showed a significant improvement as compared to the raw walnut shell. The obtained thermodynamic parameters demonstrated a spontaneous and endothermic nature of the adsorption process of SY onto walnut shell biomass. The adsorption kinetics fitted well with the pseudo-second-order model. It was concluded that intra-particle diffusion was one of the rate-controlling steps in this process. MMWS was proved to be a promising adsorbent to treat dye wastewater.