Nitrate removal from aqueous solutions by Zn/Ag bimetal-Aminosulfonic acid two-step reduction method
LIU Yan-lan1, WANG Shi-xiang1,2, FAN Qin1, HE Liang1, ZHOU An-lan1, LIU Yong1,2
1. College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, China; 2. Key Laboratory of Treatment for Special Wastewater of Sichuan Province Higher Education System, Chengdu 610066, China
Abstract：To remove nitrate from wastewater, Zn/Ag bimetal was prepared by chemical liquid reduction method and characterized by XRD and SEM. The obtained Zn/Ag bimetal was used to convert of NO3--N into NO2--N selectively. Then, the aminosulfonic acid was employed to further reduce NO2--N to N2. The optimum reduction conditions and the denitrification mechanism were proposed based on the batch experiments. For the first step, with 0.028% of Ag loading ratio, pH adjusted to 3using formic acid, 1.1g/L of EDTA-2Na dosage, 60g/L of Zn/Ag bimetal and 40min of reaction time, 81.9mg/L NO2--N and 4.0mg/L NH4+-N was obtained from 100mg/L NO3--N. For the second step, NO2--N was entirely reduced to N2by aminosulfonic acid under the conditions of the ratio of n(NH2SO3H) to n(NO2--N) at 2 to 1, pH at 6.0 and reaction time of 40min. The NO3--N removal and N2 production of the overall reaction were 93.2% and 89.3%, respectively. In addition, the NO3--N reduction by this two step reduction process produced NH4+-N as the by-product at a yield of 3.9%. The surface properties of Zn/Ag bimetallic and the solution pH played key roles for the accumulation of NO2--N, which promoted the conversion of NO3--N into N2.
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