Batch and Column Extraction of Lead from Al-Doura Oil Refinery Soil

Abstract

The aim of this research is to investigate the extraction of lead (Pb) from soil of Al-Doura oil refinery in Baghdad/Iraq. Ethylenediaminetetraacetic acid disodium salt (Na₂EDTA) and Hydrochloric acid (HCl) solution were used as extractants. Soil washing method was practiced in two ways, batch extraction and column extraction experiments. A set of batch experiments were carried out at different conditions of extractant (Na₂EDTA, HCl) concentration, contact time, pH and agitation speed. From  the batch experiments,  the maximum removal percentages of Pb that have been obtained were  70 % using Na₂EDTA (0.1M) at pH 4 , agitation speed 200 and at equilibrium time 4 hours and 65 %  using  HCl (1M) at  pH 1.08 , agitation speed 200 at equilibrium time 5 hours.                

     Column experiments were conducted at different conditions of extractant (Na₂EDTA, HCl) concentration, contact time and flow rate. The maximum removal percentages of Pb were 78% using Na₂EDTA (0.1M) at pH 4 , flow rate 30 ml/hr and equilibrium time  8 hours   and 75%  using HCl (1M) at pH 1.08, flow rate  20 ml/hr and equilibrium time 10 hours. 

     The column extraction proved that the extractant volume required to achieve high removal efficiency is less than that of the batch extraction, but requires a longer contact time.

            The experimental data of batch and column extraction were applied in four kinetic models; first order, parabolic diffusion, two constant and Elovich model to find best fit model for extraction system. For batch extraction, the parabolic diffusion and two-constant models gave the best correlation {coefficient of determination (R²)} with experimental data using HCl and Na₂EDTA respectively. While for column extraction, Elovich model gave good correlation with experimental data.