Biopolymer scaffold of pectin and alginate for the application of health hazardous fluoride removal studies by equilibrium adsorption, kinetics and thermodynamics

Abstract

About 200 million people worldwide drink groundwater containing fluoride concentrations which are above the WHO recommended a maximum permissible level of 1.5 mg/L. In this study, we have used pectin-alginate based biomaterial scaffolds (BMS) within situ functionalized trimetallic oxide Fe-Al-Ce (FAC) for adsorption of fluoride from the water. The Qe of the BMS-FAC, FAC, and BMS are 400, 142.85, and 58.82 mg/g, respectively and the surface area of BMS-FAC is 274.59 m2/g. The adsorption of fluoride follows Langmuir model and kinetics of adsorption follows pseudo-second-order and intraparticle diffusion. The adsorption was feasible, spontaneous, endothermic, and chemisorption in nature i.e. (ΔH > 0, ΔG < 0, and ΔS > 0). The better economic viability of BMS-FAC, in comparison to other adsorbents, is shown by the cost-benefit analysis. The adsorbent can be regenerated up to 10 cycles (65%), which makes this method environment-friendly. The leading mechanisms for fluoride adsorption were mainly ion-exchange, electrostatic interactions, and complexation. XPS analysis exposes the key role of the hydroxyl group on the adsorption of fluoride with the adsorbent. This novel synthesis involves cross-linking between two biopolymers by using glutaraldehyde and entrapment of trimetallic oxide in order to increase the active sites as well as the surface area, which makes this a very good adsorbent for adsorption of fluoride.