Optimization of Soil Washing Conditions using Chitosan as Chelating Agent for the Removal of Iron from Contaminated Soil by Response Surface Method

Author : Remarim, Alyssa Mae Estimada
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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Soil sample obtained from a rice field in Sta. Cruz, Zambales showed a high concentration of iron (337,738.54 mg/kg soil) exceeding the limit for agricultural soils (1000 mg/kg). In this study, soil washing using chitosan as chelating agent to remove iron from the contaminated soil was explored. Batch soil washing was employed while varying pH (1, 5), chitosan concentration (0.5 g/L, 2.5 g/L) and soil loading (0.04 g/mL, 0.20 g/mL) following a 2³ full factorial design. The effect of the factors and their interactions were evaluated using ANOVA at 95% confidence interval. pH level was found to be significant with a negative effect on iron removal while chitosan concentration and soil loading were found to be insignificant. At pH 1, 0.5 g/L chitosan concentration, and 0.04 g/mL soil loading, the highest amount of iron was removed (3,266 mg/ kg soil) while pH 5, 0.5 g/L chitosan concentration, and 0.20 g/mL soil loading, removed the lowest amount of iron (0.36 mg/kg soil). Numerical optimization using one factor design showed that the optimum soil washing conditions (pH 0.5, 0.5 g/L chitosan concentration, and 0.20 g/mL soil loading) removed 26, 733.33 mg Fe/kg soil with 3.28% error from the predicted value. Preliminary cost of batch soil washing for the removal of iron resulted to Php 0.03/mg Fe or Php 732.80/kg soil, relatively higher than the average cost for soil washing that can remove several metals, Php 18.00/kg soil. However, considering the potential removal of other metals during soil washing may lessen the cost.

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