Optimization of Soil Washing Conditions using Ethylenediaminetetraacetic Acid (EDTA) as Chelating Agent for the Removal of Chromium from Contaminated Soil by Response Surface Method
Author : Pascual, Aira Denielle Ribaño
Major Adviser : Detras, Monet Concepcion M.
Committee Members : Migo, Veronica P.; Laurio, Michael Vincent O.
Year : 2017
Month : June
Type : Thesis
Degree: BS
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Abstract
In this study, soil washing using ethylenediaminetetraacetic acid (EDTA) as chelating agent was explored on the metal-contaminated soil obtained from a rice field in Sta. Cruz Zambales to remove chromium. The metal profile of the soil sample showed that it contained 8,861.48 mg Cr/kg soil which exceeded the limit of 10 to 50 mg Cr/kg soil for agricultural soil (Shanker et al., 2005). Batch soil washing was done on the contaminated soil using EDTA at different concentrations (5×10⁻³ mol/L and 0.05 mol/L), pH (4.5 and 8), and soil loading (0.05 g/mL and 0.2 g/mL). Statistical analysis of the results showed that the EDTA concentration, pH and soil loading were significant on the amount of chromium removed as well as their 2-factor and 3-factor interactions. An increase in the amount of chromium removed was found to occur when the EDTA concentration increases and the solution pH and soil loading decreases. To maximize the amount of chromium removed, Box-Behnken Design was used to find the optimum EDTA concentration, pH and soil loading. The optimum condition was found to be at pH 5.86, 0.05 mol/L EDTA concentration, and 0.12 g/mL soil loading which was predicted to remove 21.25 mg Cr/kg soil. The preliminary cost of the soil washing process, based on chromium removal only, amounted to 230 Php/kg soil or 10.81 Php/mg Cr. The soil washing process using EDTA as the chelating agent was found to be effective in the removal of chromium up to the oxide fraction from the contaminated soil.
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