Removal of Cd(II) and Pb(II) from wastewater via carbonation of aqueous Ca(OH)(2) derived from eggshell

Abstract

Accelerated carbonation is an effective and attractive method for the utilization of captured and stored CO2. It has versatile applications in different fields. One of the applications presented in this study was investigation of the efficiency of carbonation of Ca(OH)(2) derived from waste eggshell to remove heavy metals from wastewater. Cadmium (Cd(II)) and lead (Pb(II)) were the target heavy metals for this study. Three parameters were studied: Ca(OH)(2) dosage, initial Cd(II) and Pb(II) concentration, and CO2 flow rate. The optimum conditions were 3 g/L of Ca(OH)(2), 100 mg/L of initial metal concentration and 1 L/min of CO2 flow rate where the removal efficiencies were found to be 99.99% and 99.63% for Cd(II) and Pb(II) respectively. The phase transformation has also been detected by XRD, FTIR and TGA/DTA analysis. All the results showed a transformation of Ca(OH)(2) to CaCO3 (calcite) due to complete carbonation. The transfer of CO2 during calcite formation in the presence of Pb(II) and Cd(II) was slightly retarded by a retarding factor of 0.06 and 0.09 respectively. The carbonation process was also applied to real wastewater and the performance was effective although it had very low concentrations of cadmium and lead. Precipitation of metal carbonate was the dominant mechanism for the removal of heavy metals. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.