Experimental investigation of H3PO4 activated papaya peels for methylene blue dye removal from aqueous solution: Evaluation on optimization, kinetics, isotherm, thermodynamics, and reusability studies

• Published in: Journal of environmental management 2023-11, Vol.345, p.118815-118815, Article 118815
• Main Authors: Waghmare, Charuta, Ghodmare, Sujesh, Ansari, Khalid, Dehghani, Mohammad Hadi, Amir Khan, Mohammad, Hasan, Mohd Abul, Islam, Saiful, Khan, Nadeem A., Zahmatkesh, Sasan
• Format: Article
• Language: English
• Subjects: adsorbents; Adsorption; Adsorption isotherm; Adsorption kinetics; aqueous solutions; biosorbents; Characterization techniques; environmental management; Fourier transform infrared spectroscopy; heat production; kinetics; Methylene blue; Optimization; Papaya peel; regression analysis; response surface methodology; sorption isotherms
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.118815

This investigation is centered on the effectiveness of methylene blue (MB), a cationic dye, adsorbed from an aqueous media by H3PO4 activated papaya skin/peels (PSPAC), with initial pH (2–10), contact time (30–180 min), MB dye concentration (varying from 10 to 50 mg/L), and MB dose (0.1–0.5 gm). The findings show that the best optimal conditions for MB dye removal occur at a 6 pH, 0.3 gm dose of PSPAC adsorbent for 10 mg/L MB dye concentration, with 90 min of contact time. To optimize and validate the extraction efficiency of MB dye, a response surface methodology (RSM) study was conducted using a central composite design (CCD) with a regression model showing R2 = 0.9940. FT-IR spectroscopy shows, CO, and O–H stretching functional groups while FE-SEM is assessed to supervise morphological features of the PSPAC adsorbent. The peak adsorption capacity with 46.95 mg/g for the Langmuir isotherm model conveniently satisfies the adsorption process with R2 = 0.9984 while with R2 = 0.999, a kinetic model, pseudo-second-order, confirms MB dye adsorption by PSPAC adsorbent. Moreover, thermodynamic parameters including ΔGᵒ, ΔH°, and ΔS° were computed and found to be spontaneous and exothermic. Furthermore, regeneration studies employed with NaOH (0.1 M) and HCl (0.1 M) solution media show an acceptable MB removal efficiency consecutive up to three cycles. The study highlights that H3PO4 papaya skin/peel (PSPAC) is an effectual, sustainable, reasonably available biosorbent to remove industrial cationic dyes disposal. [Display omitted] •Papaya peels activated carbon on phosphoric acid (H3PO4) to biosorb methylene blue (MB) dye.•Experimental performance exhibited a high adsorption capacity for methylene blue at 46.95 mg/g.•MB dye removal peaks at 6 pH, 0.3 gm of PSPAC adsorbent at 10 mg/L MB dye concentration, in 90 min.