Sorptive Response Profile of Chitosan Coated Silica in the Defluoridation of Aqueous Solution

Y Vijaya,A Krishnaiah

doi:10.1155/2009/748153

Abstract

As excess of fluoride (> 1.5 mg/L) in drinking water is harmful to the human health, various treatment technologies for removing fluoride from groundwater and aqueous medium have been investigated in the past. Present investigation aims to develop chitosan coated silica (CCS) and to investigate the removal of fluoride by CCS through adsorption. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Thermo gravimetric analysis (TGA), X-ray diffraction (XRD) were used for the characterization of the sorbent. The surface morphology of the CCS was observed using SEM. Series of batch adsorption experiments were carried out to assess parameters that influence the adsorption process. The factors investigated include the influence of pH, contact time, adsorbent dose and initial fluoride concentration. The studies revealed there is an enhanced fluoride sorption on CCS. The sorption data obtained at optimized conditions were subjected to Langmuir and Freundlich isotherms. The monolayer sorption capacity, Q° (44.4 mg/g) and binding energy b (0.010 L/mg) have been estimated using Langmuir isotherm. The kinetic studies indicate that the sorption of fluoride on CCS follows Pseudo second-order kinetics.

Highlights

Fluoride enters into water due to both natural processes and human activity
In order to understand the nature of fluoride sorption on chitosan coated silica (CCS) biosorbent Fourier transform infrared spectroscopy (FTIR) (Fourier Transform Infrared Spectroscopy), Scanning electron microscopy (SEM) (Scanning Electron Microscopy), Thermo gravimetric analysis (TGA) (Thermo Gravimetric Analysis) and X-ray diffraction (XRD) (X-Ray Diffraction) studies were performed
FTIR spectra of CCS before and after fluoride sorption are presented in Figure 1a and b, respectively

Summary

Introduction

Fluoride enters into water due to both natural processes and human activity. Since fluoride is present in several minerals, it can be leached out by rainwater thereby allowing it to contaminate ground and surface water. Toxic wastes containing fluorine/fluoride are generated in all industries using fluorine or its compounds as raw materials. Prominent among these is the aluminium smelter where fluoride gas is released into the atmosphere. Many countries have regions where the water contains more than 1.5 mg/L of fluoride due to its natural presence in the earth’s crust, or discharge by agricultural and industrial activities, such as steel, aluminium, glass, electroplating[5,6,7]

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