Green synthesis of carbon quantum dots from teak leaves biomass for in situ precipitation and regenerative-removal of methylene blue-dye

Zakriya Waseem Basha; Annamalai Senthil Kumar; Sarangapani Muniraj

doi:10.1007/s11356-024-32816-x

Green synthesis of carbon quantum dots from teak leaves biomass for in situ precipitation and regenerative-removal of methylene blue-dye

Environ Sci Pollut Res Int. 2024 Mar 11. doi: 10.1007/s11356-024-32816-x. Online ahead of print.

Authors

Zakriya Waseem Basha¹, Annamalai Senthil Kumar², Sarangapani Muniraj³

Affiliations

¹ P. G. & Research Department of Chemistry, RKM Vivekananda College (Autonomous), Mylapore, Chennai, 600004, Tamil Nadu, India.
² Nano and Bioelectrochemistry Research Laboratory, Carbon Dioxide and Green Technology Research Centre and Department of Chemistry, School of Advance Science, Institute of Technology University, Vellore, 632 014, Tamil Nadu, India.
³ P. G. & Research Department of Chemistry, RKM Vivekananda College (Autonomous), Mylapore, Chennai, 600004, Tamil Nadu, India. smuniraj@rkmvc.ac.in.

PMID: 38468008
DOI: 10.1007/s11356-024-32816-x

Abstract

The objective of this study was to completely eliminate environmentally harmful cationic organic dye from aqueous solutions using the one-step ultrasonication method, renowned for its energy efficiency, user-friendliness, and minimal requirement for chemical resources, making it particularly suitable for large-scale applications. To achieve effective environmental remediation, we employed carbon dots derived from teak leaf biomass (TBCDs) layered with graphene oxide. We conducted a thorough characterization of the TBCDs using UV-vis spectroscopy (with absorption peaks at λ_max = 208 and 276 nm), FTIR spectroscopy (confirming the presence of various functional groups including -OH, -CH, C = O, COO^-, C-O-C, and = C-H), Raman spectroscopy (with bands at 1369 cm^-1 (D-Band) and 1550 cm^-1 (G-Band), and an intensity ratio (I_D/I_G) = 0.88, indicating structural defects correlated with the sp³ hybridization sites on the TBCDs), XRD analysis (indicating an amorphous nature of particles), HRTEM imaging (showing homogeneous dispersal of TBCDs with typical sizes ranging from 2 to 10 nm), FESEM analysis (showing a flat surface and minuscule particles), and Zeta potential analysis (revealing a surface charge peak at -51.0 mV). Our adsorption experiments yielded significant results, with a substantial 50.1 % removal rate and an impressive adsorption capacity of 735.2 mg g^-1. Theoretical adsorption parameters were rigorously analyzed to understand the adsorption behavior, surface interactions, and mechanisms. Among these models, the Langmuir isotherm in conjunction with pseudo-second-order kinetics provided an exceptional fit (with R² values closer to 1) for our system. The Gibbs free energy (ΔG) was found to be negative at all temperatures, indicating the spontaneity of the reaction. Regarding mechanism, electrostatic attraction ((+ve) MB dye + (- ve) TBCDs), π-π stacking adsorption facilitated by the graphitic structure, formation of multiple hydrogen bonds due to polar functional groups, and a pore-filling mechanism wherein the cationic MB dye fills the pores of TBCDs with graphene oxide layers, forming an adduct were identified. Furthermore, we demonstrated the regenerative capacity of our system by effectively extracting and recovering the MB dye (with a regeneration rate of 77.1%), utilizing ethyl alcohol as the solvent. These findings not only provide valuable insights into the adsorption capabilities of TBCDs but also highlight the potential of our approach in the recovery of expensive cationic organic dye compounds from polluted environments.

Keywords: Bulk dye removal; Cationic methylene blue dye; In situ precipitation; Surface regeneration; Teak biomass derived carbon dots (TBCDs).