地下水环境因素对包覆型纳米铁降解NO_3^--N的影响

Effects of Groundwater Environmental Factors on NO_3^--N Reduction Using Coated Nano Iron

采用室内序批试验对比研究了ρ(DO)、光照、温度及初始pH等因素对油酸包覆型纳米铁材料去除地下水中NO3--N效果的影响.结果表明:模拟地下水溶解氧环境〔ρ(DO)为0.50 mg/L〕和实验室纯水溶解氧环境〔ρ(DO)为5.41 mg/L〕下,反应264h后NO3--N的去除率分别为78.9%和42.3%;模拟地下水黑暗环境和实验室自然光照下,NO3--N的去除率变化不大,反应400 h后均达到97.6%以上,反应过程中前者NO2--N的转化率是后者的1.57倍;模拟一般地下水温度(15℃)和实验室室温(25℃)环境下,反应初期,温度越高,NO3--N的降解速率越快,反应48 h后后者NO3--N的去除率是前者的2.01倍;地下水不同初始pH(分别为4、7、9)对油酸包覆型纳米铁去除NO3--N的影响较小,反应400 h后NO3--N的去除率分别为87.9%、84.5%和82.3%,反应50 h内初始pH较高环境下的pH会逐渐降低,初始pH较低环境下的pH会逐渐升高,随后pH逐渐稳定在8附近.可见,地下水低温、厌氧、黑暗的环境对包覆型纳米铁去除NO3--N存在一定的影响,在修复地下水NO3--N污染的应用研究中,有必要充分模拟地下水的环境条件,这也是获取客观理论数据的重要前提.

Oleic acid-coated nano-iron was used to remove NO3^--N from groundwater in this study. The influences of DO concentration, light, temperature and initial pH on NO3^ - -N removal efficiency were observed with sequencing batch experiments lab. The results indicated that the NO3^ - -N removal rate by oleic acid-coated nano-iron was influenced by DO concentration. The NO3^ - -N removal rates were 78.9% and 42. 3% with the corresponding DO concentration of 0. 50 and 5.41 mg/L respectively after 264 h. The NO3^ - -N removal rate was 97.6% after 400 h, and there was little difference under natural light and clark condition. However, convert efficiency of NO2^ --N under dark condition was 1.57 times that of under light condition. These reactions were significantly affected by the temperature. The removal rate of NO3^ --N at 25 ℃ was 2.01 times that of at 15 ~C after 48 h. The initial pH （pH = 4, 7, 9） had no significant effect on NO3^ --N removal efficiency using coated nano iron. The NO3 ^--N removal efficiencies in those three conditions were 87.9%, 84. 5% and 82.3%, respectively after 400 h. The value of pH decreased at high pH condition, and increased at low pH condition in the process of reaction, and finally became stable at pH around 8. Therefore, groundwater environmental factors （temoerature. anaerobic, dark） could influence the nitrate removal efficiency using coated nano iron. The simulation of groundwater environmental condition is necessary, and it could provide important reference for access of objective data in the future research.