Abstract

Preparation and Characterization of Polyalthia longifolia Based Alumina as a Novel Adsorbent for Removing Fluoride from Drinking Water

Author(s): Sanghranta S. Waghmare1*, Tanvir Arfin1, Nilesh Manwar1, Dilip H. Lataye2, Nitin Labhsetwar1 & Sadhana Rayalu1

This research addresses i) synthesis of an alumina composite based on high capacity adsorbent using a leaf as a template and ii) the issue of handling spent regenerant resulting from regeneration of such high capacity adsorbents. A low-cost composite type adsorbent has been synthesized for removal of excess fluoride from drinking water, using Polyalthia longifolia (false Ashoka tree) leaf as a template and alum as a source of alumina. The composite adsorbent having heterogeneous phases of Al(OH)3 and Al2O3 is associated with carbon and free Al(OH)3 and alumina has been identified using XRD, SEM, FTIR and BET surface area analysis. Batch adsorption experiments were carried out including the effect of various physico-chemical parameters, such as adsorbent dose, pH, contact time, initial fluoride ion concentration and temperature to ascertain optimal performance conditions. The elemental composition of material and SEM analysis suggests a composite material with different phases. Polyalthia longifolia based adsorbent (PBA) effectively removes fluoride with substantially high adsorption capacity of 17.57 mg g-1 at initial fluoride concentration of 5 mg l-1 using very low dose of 0.4 g l-1 as compared to 1.82 mg g-1 for activated alumina. PBA has been regenerated to the tune of about 80% using alum solution. The spent regenerant has been subjected to two new options i) recovery of alum and formation of chitosan/CaF composite by treating with slaked lime and ii) immobilization of AlF in chitosan to form chitosan/AlF composite. These composites may prove to be useful optic materials for UV absorption.

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