Harnessing the Waste-to-Wealth Potential of Saraca asoca Plant-Derived Nanoparticles for the Sustainable Removal of Cationic Dyes through Regenerative Adsorption

Abstract

This study showcases the successful synthesis of Saraca asoca nanoparticles (SANPs) and their efficacy as adsorbents for a range of cationic dyes, namely, malachite green (MG), methylene blue (MB), and crystal violet (CV). SANPs have been characterized through techniques such as powder X-ray diffraction, Fourier transform infrared, dynamic light scattering, scanning electron microscopy, and transmission electron microscopy. X-ray photoelectron spectroscopy analysis confirms the different oxidation states of elements, including carbon, potassium, calcium, phosphorus, silicon, and oxygen. Using the Debye–Scherrer equation, the average crystallite size has been estimated to be 27 nm. Synthesized SANPs illustrate highly effective adsorption toward MB, CV, and MG, demonstrating maximum adsorption efficiencies 495, 404, and 943 mg/g, respectively. Furthermore, the adsorption mechanism follows the pseudo-second-order reaction, and the Langmuir isotherm indicating adsorption follows chemisorption and monolayer formation. Besides this, the high efficiency may be due to the combined effect of diffusion and adsorption. To confirm practical viability and feasibility, SANPs encapsulated within alginate beads were developed that also exhibited a high MG removal efficiency with significant regenerative ability for multiple consecutive cycles. SANPs and their alginate-encapsulated beads, therefore, align with current sustainable development goals.