Philippine E-Journals

Degradation of Trichloroethylene by Zero-Valent Iron

Wilheliza A. Baraoidan | Pag-asa D. Gaspillo | Hojae Shim | Shang-tian Yang

Discipline: Engineering

 

Abstract:

The contamination of groundwater by trichloroethylene (TCE), generally used as a cleaning solvent, is still a major environmental concern. The degradation of TCE by using zero- valent metal has emerged to be a promising technology. Zero-valent iron is cheap, nontoxic, and works well in the degradation of a wide range of chlorinated compounds. Tests on the degradation of TCE by zero-valent iron were conducted to determine the effect of initial pH, TCE concentration and amount of iron on the degradation rate of TCE. Different concentrations of simulated TCE solution were mixed with iron powder, finer than 100 mesh, in 120-mL serum bottles. The ratio of iron powder (in mg) to initial TCE solution (in ml) was varied at 10, 12.5 and 15, initial concentrations of TCE, at 5, 10, 20, 60, 80 and 100 mg/L; and initial pH at 5, 7 and 9. Analyses of results showed that as the initial concentration of TCE increased, the initial degradation rate of TCE also increased. The degradation of TCE was found to be pseudo-first order with respect to the organic compound itself. The dechlorination processed worked well when the solution was initially acidic (pH=5) to almost neutral (pH=7); dechlorination was not observed when the solution was initially basic (pH=9). For a constant initial TCE concentration of 5 mg/L, rate constant (k) was related to the iron to initial TCE ratio (r) by a quadratic equation. On the other hand, when the ratio (r) was fixed at 12.5 mg Fe0 per mL of 5 mg/L TCE solution, the rate constant varied linearly with the initial TCE concentration.