Effective removal of excessive fluoride from aqueous environment using activated pods of Bauhinia variegata: Batch and dynamic analysis

• Published in: Environmental pollution (1987) Vol. 272; p. 115969
• Main Authors: Jayashree, D. Eunice, Kumar, P. Senthil, Ngueagni, P. Tsopbou, Vo, Dai-VietN, Chew, Kit Wayne
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2021
• Subjects: Activated carbon; Adsorption; Bauhinia; Bauhinia variegate; Defluoridation; Fluorides; Fluorosis; Hydrogen-Ion Concentration; Kinetics; Water; Water Pollutants, Chemical - analysis; Water Purification; Defluoridation; Fluorosis; Bauhinia variegate; Adsorption; Activated carbon
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.115969

In this study, a novel biosorbent is prepared from the pods of Bauhinia variegata is used for defluoridation of the fluoride contaminated water. It is an eco-friendly and economically feasible material. Comparison of adsorption capacity of Physically Treated Bauhinia (PTB) and Chemically Treated Bauhinia (CTB) are carried in this work. Characterization studies like SEM, EDS, FTIR, and XRD are executed to analyze surface morphology and functional groups in PTB and CTB. The experimental procedure was implemented in a batch process where the operating constraints such as dosage, pH, initial fluoride concentration, time, and temperature are varied to attain optimized efficiency. PTB and CTB yield an adsorption capacities of 10.90 mg/g and 15.45 mg/g respectively in the batch process. PTB adheres fluoride in monolayer formation whereas CTB forms multilayer adsorption. The adsorption process was described by the Pseudo first-order model to state the mechanism of physisorption. The negative values of thermodynamic parameters indicate spontaneity and favorable conditions for adsorption process. As CTB has a higher adsorption capacity than PTB, the batch study has been extended to column adsorption. Bed depth, initial fluoride concentration, and flow rate are the experimental variables used to acquire breakthrough curves. Simplified column models like Adam-Bohart, Thomas, and Yoon-Nelson models were analyzed. In column studies, Yoon-Nelson model fitted well in describing the process of adsorption. The maximum adsorption capacity acquired during the column process was found to be 1.176 mg/g with a bed depth of 5 cm and a flow rate of 5 ml/min. Thus, the innocuous and sustainable adsorbent is developed and serves as an excellent defluoridation agent. [Display omitted] •Activated carbon from Bauhinia variegata was used for defluoridation in batch and column processes.•The adsorption capacity of PTB and CTB were 10.90 mg/g and 15.74 mg/g with monolayer and multilayer mechanisms.•The negative values of ΔG °, ΔHo and ΔSo state nature of the adsorption process to be exothermic and spontaneous.•Fluoride uptake capacity of CTB was observed to be 1.176 mg/g in column study.•Yoon-Nelson model suits well for the fixed column system analysis. The effective separation of fluoride ions from water was achieved using an active material under batch and column mode of operations.