| dc.description.abstract | The purpose of this study was aimed to investigate the reaction behavior of trichloroethylene (TCE) by zero-valent iron technology. By the batch tests, effect of dissolved oxygen, initial concentration of TCE, initial pH, amounts of zero-valent iron, nitrate and humic acid were studied to understand the performance and reaction kinetics of TCE elimination. Furthermore, the analysis of scanning electron microscopy (SEM) was carried out to observed the figure of iron surface with pretreatment of removing TCE.
Experimental results indicated the effect of dissolved oxygen (2.5~7mg/L), initial concentration (1.3~61mg/L), and initial pH (3~9) was minimal for the removal and reaction rate constant of TCE elimination as the added amounts of iron was 250g/L. The average value of reaction rate constant and half-life was 0.084h-1 and 8.26hr respectively. However, the removal efficiency of TCE increased as the amounts of iron was increased. The reaction rate constant would increase 0.03h-1 per increasing 1mg/L of iron. Moreover, results revealed the removal of TCE was superior when the zero-valent iron was pretreated with the acid-washed method combining vacuum drying. The normalized rate constant (KSA) and half-live (t1/2,N, for 1m2/L) was estimated to be 1.2 10-3 h-1m-2L and 0.58hr respectively. The image of SEM also showed these grains of iron seemed to be gave greater specific surface.
In addition, the reaction of TCE elimination was inhibited when the TCE coexisted with the nitrate or humic acid. As the nitrate concentration was maintained between 20 to 100 mg/L, the inhibition condition was similar and the reaction rate constant was in the range of 0.05 to 0.06h-1. However, when the nitrate was reduced to ammonia completely, the reaction rate constant of TCE elimination increased to 0.07 ~ 0.09h-1 as well as that without the coexistence of nitrate. Also, the inhibition of TCE elimination increased with the increase of humic acid concentration. When the humic acid concentration was controlled at 100mg/L, the reaction rate constant was reduced to 30% of that without the inhibition of humic acid. | en_US |