Sesbania grandiflora activated carbon as a high-efficiency stable and reusable adsorbent for sustainable fluoride removal

BACKGROUND AND OBJECTIVE: Excess fluoride in groundwater poses environmental and public health risks, causing skeletal and dental fluorosis. Conventional defluoridation methods struggle with cost, efficiency, and reusability. This study evaluates Sesbania grandiflora activated carbon as a stable, reusable fluoride adsorbent, focusing on its characterization, optimal adsorption conditions, and reusability.METHODS: Sesbania grandiflora activated carbon was synthesized and characterized using fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction to assess structural integrity and surface interactions. Batch adsorption experiments were conducted by varying particle size (up to ۲.۳۶۰ millimeter), dosage (۲–۱۰ grams), agitation speed (۱۰۰–۵۰۰ revolution per minutes), and contact time (up to ۱۴۰ minutes) to determine the optimal conditions for fluoride removal. Adsorption isotherms and kinetics were analyzed using Freundlich and Langmuir models, while reusability was evaluated over five regeneration cycles with ۰.۱ mole sodium hydroxide.RESULTS: Fourier transform infrared spectroscopy revealed interactions between fluoride ions and surface functional groups. Scanning electron microscopy showed a porous structure (pore size ۰.۵–۵ microns) that smoothed post-adsorption, confirming fluoride uptake. Energy dispersive x-ray spectroscopy showed before treatment, Sesbania grandiflora activated carbon had ۷۸.۳ percent carbon and ۱۶.۵ percent oxygen, while after treatment, carbon increased to ۷۸.۸ percent, oxygen to ۱۷.۱ percent, and sodium rose to ۲.۱ percent, with phosphorus and sulphur undetected. X-ray diffraction confirmed that activated carbon from Sesbania grandiflora remained mostly amorphous, with crystallinity increasing from ۱۷.۲ percent to ۱۷.۴ percent. The study identified optimal adsorption conditions as ۲.۳۶۰ millimeter particle size, ۸ gram dosage, ۳۰۰ revolution per minute agitation speed, and ۱۲۰ minute contact time, achieving a maximum fluoride removal of ۸۹.۳ percent. Adsorption followed the Freundlich isotherm (coefficient of determination is ۰.۹۹۷۶), suggesting a multilayer heterogeneous adsorption process. Pseudo second order kinetics (coefficnet of determination is ۰.۹۹۸۸) confirmed chemisorption as the dominant mechanism. Sesbania grandiflora activated carbon maintained ۷۸.۳ percent efficiency after five regeneration cycles, demonstrating good reusability.CONCLUSION: Sesbania grandiflora activated carbon is a highly efficient, stable, and reusable adsorbent for groundwater fluoride removal, maintaining structural integrity and high efficiency. Its potential for scalable, sustainable water treatment warrants further study on scale-up, hybrid integration, and enhanced regeneration techniques.

کلیدواژه ها:

Adsorption isotherms ، Fluoride removal ، Groundwater treatment ، Kinetics and mechanisms ، Reusability and sustainability ، Sesbania grandiflora activated carbon