Application of melon seed shell as a natural low-cost adsorbent for the removal of Methylene Blue from dye-bearing wastewaters: optimization, isotherm, kinetic, and thermodynamic

Abstract

In this study, melon seed shells (MSS) were employed for the removal of hazardous methylene blue (MB) from the simulated wastewaters by the adsorption process. Fourier transform infrared spectra, field emission scanning electron microscope images, isoelectric pH (pH_ZPC), X-ray diffraction, and BET analysis were used to characterize the MSS biosorbent. The adsorption processes were conducted by changing the initial dye concentration, MSS dosage, pH of the solution, time, temperature, and the inorganic salts concentration as selective parameters that affect the removal efficiency. The results indicated that MB (30 mg/L) can be effectively removed (91.62%) at pH 7 and MSS dosage of 1.5 g/L after 150 min. The isotherm and kinetic parameters were also investigated, and the adsorption data were best fitted to the Temkin isotherm and pseudo-first-order kinetic model. The study of thermodynamic parameters by varying the solution temperature illustrated the endothermic and spontaneous nature of the adsorption process. The regeneration and desorption studies demonstrated the reusability of MSS for six cycles of adsorption and desorption with approximately 92% of dye removal. The overall obtained results can suggest MSS as a natural and low-cost adsorbent for the removal of cationic dyes such as MB from the contaminated effluents.

Keywords:

• Melon seed shell (MSS)
• Low-cost adsorbent
• Methylene blue
• Isotherm
• Kinetic
• Thermodynamic