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EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON
Citation:
Chen**, J. L., S R. AlAbed*, J A. Ryan*, AND Z. Li**. EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON. Bennett, G.F. (ed.), JOURNAL OF HAZARDOUS MATERIALS. Elsevier Science BV, Amsterdam, Netherlands, 83(3):243-254, (2001).
Description:
The surface normalized reaction rate constants (ksa) of trichloroethylene (TCE) and zero-valent iron (ZVI) was quantified in batch reactors at pH values between 1.7 and 10. The ksa of TCE linearly decreased from 0.044 to 0.009 L/hr-m2 between pH 3.8 and 8.0, whereas the ksa at pH 1.7 was more than an order higher than that at pH 3.8. The degradation of TCE was not observed at pH values of 9 and 10. The kas of iron hydrolysis linearly decreased from 0.092 to 0.018 L/hr-m2 between pH 4.9 and 9.8, whereas it is significantly higher at pH 1.7 and 3.8. The ksa of TCE and iron hydrolysis at a head space of 6 and 10 mL were about twice of those at zero head space. The hydrogen gas produced by iron hydrolysis partitioned into gaseous, aqueous and solid phases. The fraction of hydrogen gas entering the solid phase, which includes hydrogen bubbles formed on the ZVI surface, decreased from 80% at a head space pressure of 20 kPa to less than 30% at head space pressure above 160 kPa. The formation of hydrogen bubbles could affect the TCE degradation rate. This study suggests that lowering solution pH might not expedite the degradation rate of TCE by ZVI as it also caused faster disappearance of ZVI, and hence decreased the ZVI surface concentration.