Application of eggshell wastes for boron remediation from water

Abstract

Boron in high concentration levels leads to harmful effects on the environment and human health. Hence, it needs to be eliminated from desalinated water in order to improve water quality. As a result, the removal of boron from aqueous solution using waste eggshell as an adsorbent was investigated. Eggshell, as an agricultural waste, was studied as they are low cost and environmentally friendly, where the presence of calcium carbonate makes it an effective sorbent. The percent removal capacity of boron was studied under various experimental conditions including pH, initial boron concentration and temperature. Surface characterization, morphology and functional groups on the external surface of the adsorbent were investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). FTIR showed that the main functional groups were C=O and Ca-O on the surface of the eggshells, and SEM indicated changes in surface morphology where well defined structure was observed after calcination. However, after adsorption of boron, no significant morphology changes were detected. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models were used to deter- mine the best-fit equation to represent the experimental data. Results showed that removal efficiency of boron was 96.3% at pH 6, and the adsorption processes for both waste eggshell and calcined eggshell were exothermic and spontaneous.