Xu Jie, Pu Yuan, Qi Wei-Kang, Yang Xiao Jin, Tang Yang, Wan Pingyu, Fisher Adrian
School of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
School of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Chemosphere. 2017 Jan;166:197-202. doi: 10.1016/j.chemosphere.2016.09.102. Epub 2016 Sep 30.
Zero-valent iron has been intensively investigated in chemical reduction of nitrate in water, but the reduction requires acidic or weak acidic pH conditions and the product of the reduction is exclusively ammonium, an even more toxic substance. Zero-valent aluminum is a stronger reductant than iron, but its use for the reduction of aqueous nitrate requires considerably alkaline pH conditions. In this study, aluminum-iron alloys with an iron content of 10%, 20% and 58% (termed Al-Fe10, Al-Fe20 and Al-Fe58, respectively) were investigated for the reduction of aqueous nitrate. Al-Fe alloys were efficient to reduce nitrate in water in an entire pH range of 2-12 and the reduction proceeded in a pseudo-first order at near neutral pH conditions. The observed reaction rate constant (K) of Al-Fe10 was 3 times higher than that of Fe and the K of Al-Fe20 doubled that of Al-Fe10. The nitrogen selectivity of the reduction by Al-Fe10, Al-Fe20 and Al-Fe58 was 17.6%, 23.9% and 40.3%, respectively at pH 7 and the nitrogen selectivity by Al-Fe20 increased from 18.9% at pH 2-60.3% at pH 12. The enhanced selectivity and reactivity of Al-Fe alloys were likely due to the presence of an intermetallic Al-Fe compound (AlFe).
零价铁已被广泛研究用于水中硝酸盐的化学还原，但这种还原需要酸性或弱酸性pH条件，且还原产物仅为铵，一种毒性更强的物质。零价铝是比铁更强的还原剂，但其用于还原水中硝酸盐需要相当碱性的pH条件。在本研究中，研究了铁含量分别为10%、20%和58%的铝铁合金（分别称为Al-Fe10、Al-Fe20和Al-Fe58）对水中硝酸盐的还原作用。铝铁合金在2-12的整个pH范围内都能有效地还原水中的硝酸盐，且在接近中性的pH条件下还原反应呈准一级反应进行。观察到Al-Fe10的反应速率常数（K）比铁的高3倍，Al-Fe20的K是Al-Fe10的两倍。在pH为7时，Al-Fe10、Al-Fe20和Al-Fe58还原反应的氮选择性分别为17.6%、23.9%和40.3%，Al-Fe20的氮选择性从pH为2时的18.9%增加到pH为12时的60.3%。铝铁合金选择性和反应活性的增强可能归因于金属间化合物AlFe的存在。
