摘要
为高效地将水中硝酸盐氮(NO_3~--N)无害化去除,采用液相还原法制备了Zn/Ag双金属,利用XRD和SEM分析材料特征,并将材料用于水中NO_3~--N的初步还原,使NO_3~--N选择性地还原为NO_2~--N;再使用氨磺酸为深度还原剂,将NO_2~--N进一步还原为N_2,探讨还原过程的最佳工艺条件,初步分析该技术的脱氮机理.结果表明,在银负载率为0.028%的Zn/Ag双金属初步还原阶段,用甲酸作pH调节剂控制pH为3.0、EDTA-2Na投加量为l.lg/L、双金属投加量为60g/L、反应时间为30min的条件下还原100mg/LNO_3~--N,可得到81.9mg/L的NO_2~--N和4.0mg/L的NH_4~+-N;在深度还原阶段,在氨磺酸投加量n(NH_2SO_3H):n(NO_2~--N)为2:1,pH值为6.0,反应时间为40min的条件下,NO_2~--N的还原率为100%.整个过程的NO_3~--N去除率为93.2%,NH_4~+-N的生成率为3.9%,N_2的选择性达到89.3%.分析认为,Zn/Ag双金属的表面性质及体系的pH对NO_3~--N的还原和NO_2~--N的积累起关键作用,为NO_3~--N大量还原为N_2提供基础.
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 NO_3~--N into NO_2~--N selectively.Then,the aminosulfonic acid was employed to further reduce NO_2~--N to N_2.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 40 min of reaction time,81.9mg/L NO_2~--N and 4.0mg/L NH_4~+-N was obtained from 100mg/L NO_3~--N.For the second step,NO_2~--N was entirely reduced to N_2 by aminosulfonic acid under the conditions of the ratio of n(NH_2SO_3H) to n(NO_2~-- N) at 2 to 1,pH at 6.0 and reaction time of 40 min.The NO_3~--N removal and N_2 production of the overall reaction were 93.2%and 89.3%,respectively.In addition,the NO_3~--N reduction by this two step reduction process produced NH_4~+-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 NO_2~-- N,which promoted the conversion of NO_3~-- N into N_2.
引文
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