Treatment of 1,2-dibromo-3-chloropropane and nitrate-contaminated water with zero-valent iron or hydrogen/palladium catalysts

The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compared. DBCP reacted with iron powder (100–200 mesh, 36 g/l) in HEPES-buffered water (pH = 7.0) with a t1/2 of 2.5 min and in different groundwaters (pH = 8.2–8.7) with a t1/2 ranging from 41–77 min. Dissolved O2 and NO−3 slowed the transformation, whereas sulfate and nitrite had little effect. Iron removed 60 mg/l of nitrate within 14 min with nitrite as an intermediate. In 75 ml groundwater containing 22.5 mg 1% Pd-alumina catalyst under 10% H2 partial pressure, DBCP was transformed to propane within minutes. The rate in groundwater was slower by about 30% compared to Milli-Qtm water. SO2−4, NO−3, Cl− or O2 added to Milli-Q water only slightly inhibited DBCP transformation by H2/Pd-alumina, while SO2−3 had a much stronger inhibitory affect.