Zn/Ag-氨磺酸两步还原去除水中硝酸盐氮
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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.
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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[2]Kunwar P S,Arun K S,Shikha G.Optimization of nitrate reduction by EDTA catalyzed zero-valent bimetallic nanoparticles in aqueous medium[J].Environmental Science and Pollution Research,2012,19:3914-3924.
[3]Kim M S,Chung S H,Yoo C J,et al.Catalytic reduction of nitrate in water over Pd-Cu/Ti O2catalyst:Effect of the strong metalsupport interaction(SMSI)on the catalytic activity[J].Applied Catalysis B:Environmental,2013,142-143:354-361.
[4]Soares O S G P,Orfao J J M,Pereira M F R.Activated carbon supported metal catalysts for nitrate and nitrite reduction in water[J].Catalysis Letters,2008,126:253-260.
[5]Rodriguez-Maroto JM,Garcia-Herruzo F,Garcia-Rubio A,et al.Kinetics of the chemical reduction of nitrate by zero-valent iron[J].Chemosphere,2009,74:804-809.
[6]Belay T A.Chemical reduction of nitrate by monometallic Cu(0)and bimetallic Cu/Al particles:kinetics and reaction mechanisms[D].台湾:国立台湾科技大学,2015.
[7]Kang H Y,Xiu Z M,Sun L L,et al.Chemical reduction of nitrate by nanoscale Fe/Ni bimetallic particles[J].Chinese Journal of Geochemistry,2006,25(1):111-112.
[8]Ramavandi B,Mortazavi S B,Moussavi G,et al.Experimental investigation of the chemical reduction of nitrate ion in aqueous solution by Mg/Cu bimetallic particles[J].Reaction Kinetics Mechanisms and Catalysis,2011,102:313-329.
[9]高建峰.水中硝酸盐氮复合催化还原无害化的原理和技术研究[D].天津:南开大学,2004.
[10]肖沃辉,黄羽飞,马倩玲.用氨磺酸处理亚硝酸盐废水的研究[J].矿治,2005,14(1):70-73.
[11]肖义夫,廖百森,赵舰,等.锌粒还原法快速测定食品中的硝酸盐[J].中国食品卫生,2003,15(4):316-317.
[12]GB 7480-87水质硝酸盐氮的测定酚二磺酸分光光度法[S].
[13]GB 7493-87水质亚硝酸盐氮的测定分光光度法[S].
[14]HJ 535-2009水质氨氮的测定纳氏试剂分光光度法[S].
[15]HJ 479-2009环境空气氮氧化物(一氧化氮和二氧化氮)的测定盐酸萘乙二胺分光光度法[S].
[16]de Oliveira G M,Carlos I A.Silver-Zinc electrodeposition from a thiourea solution with added EDTA or HEDTA[J].Electrochamica Acta,2009,54:2155-2163.
[17]Hamid S,Kumar M A,Lee W.Highly reactive and selective Sn-Pb bimetallic catalyst supported by nanocrystalline ZSM-5for aqueous nitrate reduction[J].Applied Catalysis B:Environmental,2016,187:37-46.
[18]Zhao W R,Zhu X,Wang Y,et al.Catalytic reduction of aqueous nitrate by metal supported catalysts on Al particles[J].Chemical Engineering Journal,2014,254:410-417.
[19]Hasnat M A,Ben Aoun S,Nizm Uddin S M,et al.Copperimmobilized platinum electrocatalyst for the effective reduction of nitrate in a low conductive medium:Mechanism,adsorption thermodynamics and stability[J].Applied Catalysis A:General,2014,478:259-266.
[20]Yun Y P,Li Z F,Chen Y H,et al.Reduction of nitrate in secondary effluent of wastewater treatment plants by Fe0reductant and Pd-Cu/graphene catalyst[J].Water Air and Soil Pollution,2016,227:111.
[21]Yang Y,Scenini F,Curioni M.A study on magnesium corrosion by real-time imaging and electrochemical methods:relationship between local processes and hydrogen evolution[J].Electrochimica Acta,2016,198:174-184.
[22]Liu J H,Huang C X,Wu S D,et al.Tensile deformation and fracture behaviors of high purity polycrystalline zinc[J].Materials Science and Engineering:A,2008,490(1/2):117-125.