Removal of cationic and anionic toxic pollutants from simulated solutions using Sterculia foetida pod (SFP): equilibrium isotherm, kinetics, and characterization

Abstract

The present work explores the sorption performance of Sterculia foetida pod (SFP) for the removal of methylene blue (MB) and chromium (Cr⁶⁺) from simulated solutions separately. The material characteristics namely textural analysis (specific surface area: 2.45 m²/g), morphological behavior (heterogeneous morphology containing pores and cavities), functional analysis (COO– stretching, C–O–C stretching vibrations, and –OH stretching) and thermal behavior (279.4 °C) were examined by various analytical techniques namely BET, SEM, FTIR, and TGA. Using non-linear Langmuir isotherm analysis, the maximal sorption capacity of SFP for the removal of MB and Cr⁶⁺ was predicted to be 74.1 mg/g and 27.3 mg/g, respectively. The optimized condition for sorption of MB and Cr⁶⁺ onto SFP was: dosage: 0.07 mg/L, initial pH: 7 (MB), and 2 (Cr⁶⁺). Thermodynamic data analysis confirmed the endothermic, favorable, spontaneous, and physisorption nature of sorption. The SFP has shown significant regeneration capacity in the consecutive runs (MB: 92.5% removal till 5th trial; Cr⁶⁺: 97.6% removal till 3rd trial). Based on these findings, SFP is a promising low-cost and eco-friendly candidate for the removal of anionic and cationic toxic pollutants in the absence of energy and chemical expenditure.

NOVELTY STATEMENT

1. Sterculia foetida pod (SFP) explored for the removal of anionic and cationic toxic pollutants in the absence of energy and chemical expenditure.

2. Mechanism for the interaction between toxic pollutants and SFP was predicted.

3. Better sorption capacity (MB: 74.1 mg/g; Cr⁶⁺: 27.8 mg/g) and better regeneration capacity (MB: 92.5% for 5th trial; Cr⁶⁺: 97.6% for 3rd trial) was achieved.

4. A feasible and spontaneous nature of sorption process toward the removal of MB and Cr⁶⁺ was demonstrated using thermodynamic relations.

Keywords:

• Chromium
• methylene blue
• regeneration
• sorption
• Sterculia foetida
• thermodynamics

Acknowledgments

All authors are thankful to the Management SASTRA Deemed to be University, Thanjavur, Tamil Nadu, India for providing the necessary facilities. We thank Dr. K. Abirami Assistant Prof. SASHE, SASTRA Deemed to be University, Thanjavur, for providing language assistance.

Author contributions

Saroja Pasupathi: methodology, investigation, formal analysis, data curation, and writing – original draft. Sameeha Syed Abdul Rahman: writing and data curation. Sugumaran Karuppiah: supervision, writing – review and editing, conceptualization, and project administration.

Disclosure statement

No potential conflict of interest was reported by the author(s).