Application of longan shell as non-conventional low-cost adsorbent for the removal of cationic dye from aqueous solution

•The adsorption potential of longan shell for the methylene blue from aqueous solution was studied for the first time..•The different experimental factors were investigated to study the adsorption process.•The kinetic data and the equilibrium data were discussed by different kinetic and isotherm models, respectively..•The thermodynamic parameters have been calculated and discussed.

With simple physical treatment, adsorption potential of longan shell for the methylene blue (MB) from aqueous solution was studied as a low-cost material under the conditions of adsorbent dosage (1–6 g/L), initial solution pH (2–12), contact time (5–180 min), temperature (293, 313, 313 K) and initial dye concentration (100–500 mg/L). The SEM images and FTIR spectra of longan shell before and after dye adsorption were analyzed to understand the adsorption process of MB onto longan shell. The kinetic data and the equilibrium data were simulated by different kinetic and isotherm models, respectively. The results showed that the adsorption process was well described by the pseudo-second-order kinetic model, and the experimental equilibrium data were better fit to Langmuir equation than Freundlich equation with the maximum adsorption capacity of 141.04 mg/g. In addition, main activation parameters (Ea, ΔH#, ΔS# and ΔG#) and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the absorption process were also determined.

Graphical abstractIn this manuscript, we focus on assessing the suitability and efficiency of longan shell for the removal of cationic dye methylene blue from aqueous solutions for the first time. The experimental factors such as initial solution pH, initial concentration of the dye, adsorbent dose, contact time, and temperature were investigated to study the adsorption process. The adsorption kinetics was discussed in view of four kinetics models and the experimental equilibrium data were tested by two isotherm models. The thermodynamic parameters have been calculated and discussed. The results showed that longan shell was a very efficient, eco-friendly and low cost adsorbent.Figure optionsDownload full-size imageDownload as PowerPoint slide