Optimization of Soil Washing Conditions using Chitosan for the Removal of Nickel from Contaminated Soil

Author : Tiongco, Diance Clare Manlangit
Major Adviser : Detras, Monet Concepcion M.
Major Co-Adviser : Migo, Veronica P.
Committee Members : Alfafara, Catalino G.; Laurio, Michael Vincent O.
Year : 2016
Month : June
Type : Thesis
Degree: BS
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Contamination of heavy metals in soil is one of the major causes of environmental pollution throughout the world. These heavy metals have the ability to persist in soil for decades, which would accumulate in biological systems and would cause environmental disaster and health problems over time. This study therefore aimed to use soil washing technology using chitosan to effectively remove the heavy metals from the soil. Initially, nickel-contaminated soils were sampled from Sta. Cruz, Zambales, with about 7,658.41 mg Ni/kg soil, exceeding the tolerance limit of 100 mg Ni/kg in agricultural soils. Batch soil washing experiments were conducted using chitosan at various solution concentrations (0.1 to 3 g chitosan/L solution), pH level (1 to 5), and solution to soil ratio (10 mL/g to 25 mL/g). Results from soil washing showed that the amount of nickel extracted from the contaminated soil ranged from 0.11 mg Ni/kg soil to 1897.5 mg Ni/kg soil. Optimization of soil washing conditions at 0.1 g chitosan/L solution, with pH 0.5 and solution to soil ratio of 10 mL/g indicated that the amount removable nickel from the soil was about 2332.23 mg/kg, with a deviation of 7.38% error from the actual value. The preliminary cost of soil washing using chitosan at optimum conditions was estimated at Php 1.95/mg Ni removed, a reasonable price considering that soils were amended with minimum environmental risks, and nickel was removed from the contaminated soil.

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