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ABSTRACT
This study deals with the elimination of hexavalent chromium from simulated solution using Acacia auriculiformis shells and its different modified forms as potent biosorbents. The raw plant biomass (RAA) was modified with sulphuric acid and named as sulphuric acid-activated carbon (SAA) and was further complexed with a chelating reagent ethylenediaminetetraacetic acid (SAAC) to further modify its sorption capacity. Adsorption parameters like pH, adsorbent dosage, temperature and initial metal concentration were optimised in batch study. The optimised data were further equilibrated using isotherm, kinetic and thermodynamic models to determine the nature of the sorbent–sorbate interaction. Langmuir isotherm showed the best fit with maximum Langmuir adsorption capacities being 91.48, 117.75 and 145.72 mg/g for RAA, SAA and SAAC respectively at pH 2. From the correlation coefficients of the fitted kinetic models, the sorbent–sorbate interaction followed pseudo-second order and is chemisorption in nature. Thermodynamic analysis verifies endothermic interaction with elevated degree of randomness. The adsorbents were regenerated for four cycles and the biosorbents proved potent for efficient sorption of Cr(VI). For SAAC, the removal efficiency decreased from 57.51% to 26.81% after fourth cycle which is more than twice and thrice as compared to SAA and RAA.
GRAPHICAL ABSTRACT
Acknowledgment
The assistance with high throughput instrumentation of The Central Instrumentation Facility, Indian Institute of Technology Guwahati, is thus highly appreciated.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Notes on contributors
Tasrin Shahnaz is a Research Scholar in the Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India. Her principal research interests are Simultaneous biosorption of heavy metals, dye, antibiotics mixture complemented by modelling studies, kinetic and thermodynamic perspective.
Chandi Patra is a Research Scholar in the Department of Biosciences and Bioengineering, IIT Guwahati, Guwahati, India. His research work involves biosorption of metal, dye, antibiotics using novel biosorbents in batch and continuous mode.
Vivek Sharma is a Research Scholar in the Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, India. He is currently pursuing his research interest in “Crystallization induced structure development in polymer nanocomposites”.
Dr. N. Selvaraju is an Assistant Professor in the Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Assam, India. Previously, he worked at National Institute of Technology, Calicut, Kerala, India. He has very good expertise in the field of Environmental bioremediation via Adsorption/Biosorption, Bioaerosol modeling and simulation, Microfluidics and Micro Reactors (Liquid-liquid operations) and Biodiesel.