Insights Into the Adsorptive, Model Validation and Mechanistic Behavior of Alkalinated Pumpkin Seed Shells Biosorbent into Remediation of Cationic Dyes

Fahim, Azza AH; El-Gharkawy, Elsayed RH; Abdel-Ghani, Ghada E.; Akl, Magda A

doi:10.21608/ejchem.2025.342201.10939

Insights Into the Adsorptive, Model Validation and Mechanistic Behavior of Alkalinated Pumpkin Seed Shells Biosorbent into Remediation of Cationic Dyes

Document Type : Original Article

Authors

Department of Chemistry, Faculty of Science, Mansoura University, Mansoura 31556, Egypt

10.21608/ejchem.2025.342201.10939

Abstract

This study presented the synthesis of effective modified biosorbent from pumpkin seed shells treated with sodium hydroxide (PSSN) to eliminate Crystal Violet (CV), Methyl Green (MG), and Toluidine Blue (TBO) dyes from water samples. Initially, the PSS (pumpkin seed shells) wastes were collected, crushed, and sieved until they reached the proper size. Then, the obtained PSS powder undergoes the modification step with NaOH to yield PSSN. Many techniques were utilized to analyze the PSS and PSSN materials before and after the adsorption process like scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller specific surface area (SBET), and Energy-dispersive X-ray spectroscopy (EDS). Different parameters affecting the adsorption process of all three dyes CV, MG, and TBO were studied. Because of the higher correlation coefficient (R2 ≥ 0.99) and lower error functions, the equilibrium CV, MG, and TBO adsorption isotherms fitted Langmuir with dyes maximum adsorption capacity reaching to 179.669, 371.22, and 190.072 mg/g for CV, MG, and TBO, respectively. Moreover, the RL values obtained for the three dyes lie between 0 and 1, indicating that CV, MG, and TBO adsorption by PSSN is a favorable process. Moreover, the error function values for the pseudo-2nd order are much lower than those for the pseudo-1st order, indicating that the adsorption of CV, MG, and TBO onto PSSN biosorbent followed the pseudo-2nd order kinetic mode. It was concluded that from the thermodynamic investigations, the CV, MG, and TBO adsorption was spontaneous, exothermic, and had less randomness. Moreover, the PSSN could be reutilized up to 5 successive cycles maintaining adsorption efficiency > 87%. Finally, the PSSN biosorbent was able to adsorb the CV, MG, and TBO dyes through four different mechanisms: π-π stacking, electrostatic attraction, hydrogen bonding, and pore diffusion.

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