Removal of Methylene Blue Dye from Aqueous Solutions Using Cordia Myxa Fruits as a Low-Cost Adsorbent

Abstract

The dyes make water harmful to humans, animals, and plants and cannot be used until treated. To treat the dyes, non-conventional methods are required, one of which is adsorption with activated carbon. This study aims to produce activated carbon from Cordia myxa fruit (CM) as a low-cost adsorbent to remove methylene blue dye (MB) from aqueous solutions. The characterization of the fabricated-activated carbon was carried out by Brunauer-Emmett-Teller (BET), Fourier-transformed infrared (FTIR), scanning electron microscope (SEM), and X-ray diffraction (XRD) analyses. Different parameters, such as pH (3-9), biochar dose (0.5-5)g/L, initial dye concentration (2-25 mg/L), temperature (25°C), and contact time (0-100 minutes), were examined in batch adsorption experiments. The results showed that the MB dye had a maximum removal efficiency of 68% at a pH of 8, a biochar dosage of 2 g/L, a dye concentration of 30 mg/L, and an 80-minute contact time. The experimental data were analyzed using the Freundlich and Langmuir isotherm models, and their compatibility with the Langmuir isotherm model (R2=0.9989) was excellent. The study of adsorption kinetics used pseudo-first-order, pseudo-second-order, and Elovich models. The results indicated that the pseudo-second-order was the best model to describe adsorption, with R2 and K2 values of 0.99 and 0.0397 g/mg. min, respectively. The negative change in Gibbs free energy (G°) showed spontaneous interaction.