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近年来,我国海水循环水养殖因高效节能、环境友好等优势发展迅速[1],但养殖循环水盐度高、养殖系统水力停留时间短、传统的生物处理法易出现氨氮及亚硝氮积累的问题,当氨氮含量超过0.2 mg·L−1会对水生生物造成毒害作用[2],因此,传统的水处理技术难以达到有效处理养殖循环水的目的。为了更好的处理养殖循环水,发展出了一系列新型处理技术,如生物滤器优化[3]、臭氧氧化[4]、电化学氧化等[5]。电化学氧化去除海水养殖循环水中的氨氮具有显著优势,不仅由于海水的高电导率降低了能耗,高氯离子浓度也保证了较高的间接氧化效率,使电化学氧化法在循环水养殖系统中的应用成为可能[6-7]。
电化学氧化过程与电极材料的催化活性及对目标污染物的选择性有直接关系,选择电活性高的催化剂可以增强电氧化效率。在各种电极材料中,Pt由于具有较高催化脱氢能力而成为目前最为理想的氨氮电催化材料[8]。反应中间产物Nads能够化学强吸附在电极表面,从而使催化活性下降;此外,Nads极大地消除了活性位点的数量,阻止氨在失活电极上氧化。由于Pt价格昂贵且资源匮乏,一般可将Pt负载在载体上以达到降低成本的目的,而且合适的载体可以削弱Nads在Pt上的吸附[9]。碳作为最常见的纳米颗粒载体具有比表面积大、电导率高和成本低等特点。但惰性材料不会增强电催化活性,而氮原子在外层轨道上比碳原子多一个电子,可增强复合碳材料的给电子能力,从而增强其催化活性[10]。因此,研究人员将碳与氮掺杂作为纳米颗粒载体[11]。Ribeiro等研究表明,Pt/CN 5上2 h的电流密度比Pt/C高约400%,碳掺杂氮载体对Pt纳米粒子的电氧化性能有改善作用[12]。
为了提高电催化氧化法处理海水养殖循环水中氨氮的效率,本文采用碳掺杂氮(CN)作为Pt纳米颗粒的载体,制备并优化复合电氧化催化剂CN-Pt,通过电催化氧化法处理模拟海水养殖循环水,研究电压、转速、催化剂负载试剂浓度、pH参数对氨氮去除率的影响并优化实验条件;同时考察电解过程中可能产生的羟基自由基、硫酸根自由基、活性氯等活性氧化物质对氨氮去除的影响,为电化学氧化技术在海水养殖循环水处理中的应用提供技术参考。
CN负载Pt电催化氧化去除海水养殖循环水中氨氮
Ammonia removal in aquaculture recirculating seawater by electrocatalytic oxidation of CN supported Pt modified anode
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摘要: 本研究制备CN负载Pt催化剂(CN-Pt)电催化氧化高效去除海水养殖循环水中的氨氮。结果表明,优化催化剂组分为CN1+15%Pt时,氨氮的电催化活性最高,氧化起始电位为−0.34 V vs. Hg/HgO;通过正交试验得出,最优实验参数为催化剂负载试剂浓度C0 100 mg·mL−1、阳极电势1.7 V vs. SCE、转速300 r·min−1、pH 10;该实验条件下处理模拟海水养殖循环水,20 min氨氮去除率为79.89%。氨氮去除的主要作用因子是活性氯,无羟基自由基或硫酸根自由基的作用。在不改变pH条件下对实际养殖循环水进行处理,40 min氨氮去除率达97.04%。CN-Pt改性阳极电催化氧化去除海水养殖循环水中的氨氮效率高、易于操控,在循环水养殖系统的水处理中具有较大的应用潜力。Abstract: In this study, platinum nanoparticles supported on nitrogen-doped activated charcoal powder (CN-Pt) was prepared for efficient ammonia removal in mariculture recirculating seawater by electrocatalytic oxidation. The catalyst CN1+15%Pt showed the highest electrocatalytic activity of ammonia oxidation. The oxidation onset potential was −0.34 V vs. Hg/HgO. The orthogonal experiment indicated the optimal parameters were C0 100 mg·mL−1, anodic potential 1.7 V vs. SCE, rotational speed 300 r·min−1, and pH 10. Under these conditions, the ammonia removal rate was 79.89% in 20 min for the simulated aquaculture recirculating water treatment. The main functional factor is active chlorine, not hydroxyl radical nor sulfate radical. Treatment of actual aquaculture recirculating water without changing the pH, the ammonia removal rate reached 97.04% in 40 min. The CN-Pt modified anode electrocatalytic oxidation is used to remove ammonia in the recirculating seawater, this method is efficient and easy to operate, and of great application potential in the water treatment of recirculating aquaculture system (RAS).
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Key words:
- ammonia /
- active oxygen species /
- electrochemical oxidation /
- Pt /
- recirculating aquaculture system
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图 4 循环伏安图(CV) (a)不同催化剂在KOH (1 mol·L− 1)中; (b)不同催化剂在KOH (1 mol·L− 1)+ NH3·H2O (0.5 mol·L− 1)中; (c)不同催化剂在KOH (1 mol·L− 1)+ NH4Cl (0.5 mol·L− 1)中; (d)CN1+15%Pt在不同电解液中; (e) (f)不同催化剂在−0.2 V (vs. Hg/HgO)、KOH (1 mol·L− 1)+ NH4Cl (0.5 mol·L− 1)电解质中的计时安培结果及局部放大图
Figure 4. Cyclic voltammogram (CV) (a)of different catalysts in KOH (1 mol·L− 1); (b)of different catalysts in KOH (1 mol·L− 1)+ NH3·H2O (0.5 mol·L− 1); (c)of different catalysts in KOH (1 mol·L− 1)+ NH4Cl (0.5 mol·L− 1); (d)of CN1+15%Pt in different electrolytes; (e)Chronoamperometric results at −0.2 V (vs. Hg/HgO)for different catalysts and (f)partial enlarged detail
表 1 正交实验表
Table 1. Orthogonal experimental Table
水平
LevelA 电压/V
PotentialB 转速/(r·min−1)
SpeedC 催化剂负载试剂浓度/(mg·mL−1)
Catalyst loading reagent concentrationD pH 1 1.3 0 10 6 2 1.5 300 20 8 3 1.7 600 100 10 表 2 正交实验结果及分析表
Table 2. Orthogonal experimental results and analysis table
实验号
Experiment1 2 3 4 出水氨氮浓度/(mg·L− 1)
Ammonia concentration
in effluent电压/V
Potential转速/(r·min− 1)
Speed催化剂负载试剂浓度/(mg·mL− 1)
Catalyst loading reagent concentrationpH 1 1.3 0 10 6 2.74 2 1.3 300 20 8 1.99 3 1.3 600 100 10 0.02 4 1.5 0 20 10 2.55 5 1.5 300 100 6 0.15 6 1.5 600 10 8 2.56 7 1.7 0 100 8 0.98 8 1.7 300 10 10 0.08 9 1.7 600 20 6 0.06 kgp kg1 4.75 6.27 5.38 2.96 kg2 5.26 2.22 4.60 5.53 kg3 1.12 2.63 1.15 2.64 Kgp Kg1 1.58 2.09 1.79 0.99 Kg2 1.75 0.74 1.53 1.84 Kg3 0.37 0.88 0.38 0.88 Rg 1.38 1.35 1.41 0.96 -
[1] 刘鹰. 海水工业化循环水养殖技术研究进展 [J]. 中国农业科技导报, 2011, 13(5): 50-53. doi: 10.3969/j.issn.1008-0864.2011.05.08 LIU Y. Research progress on marine industrial recirculating aquaculture technology [J]. Journal of Agricultural Science and Technology, 2011, 13(5): 50-53(in Chinese). doi: 10.3969/j.issn.1008-0864.2011.05.08
[2] PRZYBYLKO A R M, THOMAS C L P, ANSTICE P J, et al. The determination of aqueous ammonia by ion mobility spectrometry [J]. Analytica Chimica Acta, 1995, 311(1): 77-83. doi: 10.1016/0003-2670(95)00177-2 [3] 张海耿, 张宇雷, 张业韡, 等. 循环水养殖系统中流化床生物滤器净水效果影响因素 [J]. 环境工程学报, 2013, 7(10): 3849-3855. ZHANG H G, ZHANG Y L, ZHANG Y W, et al. Influencing factors of purifying effluent of recirculating aquaculture system by fluidized-sand biofilter [J]. Chinese Journal of Environmental Engineering, 2013, 7(10): 3849-3855(in Chinese).
[4] 姜妍君, 强志民, 董慧峪, 等. 海水循环养殖系统水处理工艺综述 [J]. 环境化学, 2013, 32(3): 410-418. JIANG Y J, QIANG Z M, DONG H Y, et al. Water treatment processes in marine recirculating aquaculture systems: A review [J]. Environmental Chemistry, 2013, 32(3): 410-418(in Chinese).
[5] 宋协法, 边敏, 黄志涛, 等. 电化学氧化法在循环水养殖系统中去除氨氮和亚硝酸盐效果研究 [J]. 中国海洋大学学报(自然科学版), 2016, 46(11): 127-135. SONG X F, BIAN M, HUANG Z T, et al. Studies of the ammonia and nitrite removal by electrochemical oxidation in recirculating aquaculture system [J]. Periodical of Ocean University of China, 2016, 46(11): 127-135(in Chinese).
[6] LAHAV O, BEN ASHER R, GENDEL Y. Potential applications of indirect electrochemical ammonia oxidation within the operation of freshwater and saline-water recirculating aquaculture systems [J]. Aquacultural Engineering, 2015, 65: 55-64. doi: 10.1016/j.aquaeng.2014.10.009 [7] 叶章颖, 裴洛伟, 林孝昶, 等. 微电流电解去除养殖海水中氨氮效果 [J]. 农业工程学报, 2016, 32(1): 212-217. doi: 10.11975/j.issn.1002-6819.2016.01.030 YE Z Y, PEI L W, LIN X C, et al. Ammonia removal effect by using micro-current electrolysis in aquaculture saline water [J]. Transactions of the Chinese Society of Agricultural Engineering, 2016, 32(1): 212-217(in Chinese). doi: 10.11975/j.issn.1002-6819.2016.01.030
[8] de VOOYS A C A, KOPER M T M, van SANTEN R A, et al. The role of adsorbates in the electrochemical oxidation of ammonia on noble and transition metal electrodes [J]. Journal of Electroanalytical Chemistry, 2001, 506(2): 127-137. doi: 10.1016/S0022-0728(01)00491-0 [9] WANG Y H, YANG Z H, YANG J, et al. Towards continuous ammonia electro-oxidation reaction on Pt catalysts with weakened adsorption of atomic nitrogen [J]. International Journal of Hydrogen Energy, 2020, 45(41): 21816-21824. doi: 10.1016/j.ijhydene.2020.05.180 [10] DAEMS N, SHENG X, VANKELECOM I J, et al. Metal-free doped carbon materials as electrocatalysts for the oxygen reduction reaction[J]. Journal of Materials Chemistry A[J]. Journal of Materials Chemistry A, 2014, 2(12): 4085-4110. [11] LIU S H, WU M T, LAI Y H, et al. Fabrication and electrocatalytic performance of highly stable and active platinum nanoparticles supported on nitrogen-doped ordered mesoporous carbons for oxygen reduction reaction [J]. Journal of Materials Chemistry, 2011, 21(33): 12489. doi: 10.1039/c1jm11488c [12] RIBEIRO V A, de FREITAS I C, NETO A O, et al. Platinum nanoparticles supported on nitrogen-doped carbon for ammonia electro-oxidation [J]. Materials Chemistry and Physics, 2017, 200: 354-360. doi: 10.1016/j.matchemphys.2017.07.088 [13] ASSUMPÇÃO M H M T, PIASENTIN R M, HAMMER P, et al. Oxidation of ammonia using PtRh/C electrocatalysts: Fuel cell and electrochemical evaluation [J]. Applied Catalysis B: Environmental, 2015, 174/175: 136-144. doi: 10.1016/j.apcatb.2015.02.021 [14] SILVA J C M, da SILVA S G, de SOUZA R F B, et al. PtAu/C electrocatalysts as anodes for direct ammonia fuel cell [J]. Applied Catalysis A: General, 2015, 490: 133-138. doi: 10.1016/j.apcata.2014.11.015 [15] LOMOCSO T L, BARANOVA E A. Electrochemical oxidation of ammonia on carbon-supported bi-metallic PtM (M = Ir, Pd, SnOx) nanoparticles [J]. Electrochimica Acta, 2011, 56(24): 8551-8558. doi: 10.1016/j.electacta.2011.07.041 [16] ZHANG L, LI F. Helical nanocoiled and microcoiled carbon fibers as effective catalyst supports for electrooxidation of methanol [J]. Electrochimica Acta, 2010, 55(22): 6695-6702. doi: 10.1016/j.electacta.2010.06.002 [17] dos REIS F V E, ANTONIN V S, HAMMER P, et al. Carbon-supported TiO2-Au hybrids as catalysts for the electrogeneration of hydrogen peroxide: Investigating the effect of TiO2 shape [J]. Journal of Catalysis, 2015, 326: 100-106. doi: 10.1016/j.jcat.2015.04.007 [18] SONG J, LIU L F, ZHANG G Q, et al. Oxygen reduction at carbon nanotubes (CNTs)/cobaltous phthalocyanine (CoPc) and MFC electricity generation affected by air-cathode catalyst layer structure [J]. Journal of the Electrochemical Society, 2016, 163(10): F1209-F1216. doi: 10.1149/2.0761610jes [19] ALI M, WITKOWSKA A, ABBAS M, et al. Evolution of the nanostructure of Pt and Pt-Co polymer electrolyte membrane fuel cell electrocatalysts at successive degradation stages probed by X-ray photoemission [J]. Journal of Power Sources, 2014, 271: 548-555. doi: 10.1016/j.jpowsour.2014.08.028 [20] DU X W, LUO S P, DU H Y, et al. Monodisperse and self-assembled Pt-Cu nanoparticles as an efficient electrocatalyst for the methanol oxidation reaction [J]. Journal of Materials Chemistry A, 2016, 4(5): 1579-1585. doi: 10.1039/C5TA09261B [21] JIANG L, HSU A, CHU D, et al. Ethanol electro-oxidation on Pt/C and PtSn/C catalysts in alkaline and acid solutions [J]. International Journal of Hydrogen Energy, 2010, 35(1): 365-372. doi: 10.1016/j.ijhydene.2009.10.058 [22] GOOTZEN J F E, WONDERS A H, VISSCHER W, et al. A DEMS and cyclic voltammetry study of NH3 oxidation on platinized platinum [J]. Electrochimica Acta, 1998, 43(12/13): 1851-1861. [23] ASSUMPÇÃO M H M T, da SILVA S G, de SOUZA R F B, et al. Investigation of PdIr/C electrocatalysts as anode on the performance of direct ammonia fuel cell [J]. Journal of Power Sources, 2014, 268: 129-136. doi: 10.1016/j.jpowsour.2014.06.025 [24] SONG J, YIN Y M, LI Y H, et al. In-situ membrane fouling control by electrooxidation and microbial community in membrane electro-bioreactor treating aquaculture seawater [J]. Bioresource Technology, 2020, 314: 123701. doi: 10.1016/j.biortech.2020.123701 [25] LI L, LIU Y. Ammonia removal in electrochemical oxidation: Mechanism and pseudo-kinetics [J]. Journal of Hazardous Materials, 2009, 161(2/3): 1010-1016. [26] F ARAÚJO K C, P BARRETO J P, CARDOZO J C, et al. Sulfate pollution: Evidence for electrochemical production of persulfate by oxidizing sulfate released by the surfactant sodium dodecyl sulfate [J]. Environmental Chemistry Letters, 2018, 16(2): 647-652. doi: 10.1007/s10311-017-0703-6 [27] 刘敏. 氨氮电氧化技术及其在养猪废水中的应用研究[D]. 上海: 上海大学, 2014. LIU M. Electro-oxidation technology for ammonia removal and its application in swine wastewater[D]. Shanghai: Shanghai University, 2014(in Chinese).
[28] 戴慧旺, 陈建新, 苗笑增, 等. 醇类对UV-Fenton体系羟基自由基淬灭效率的影响 [J]. 中国环境科学, 2018, 38(1): 202-209. doi: 10.3969/j.issn.1000-6923.2018.01.024 DAI H W, CHEN J X, MIAO X Z, et al. Effect of alcohols on scavenging efficiencies to hydroxyl radical in UV-Fenton system [J]. China Environmental Science, 2018, 38(1): 202-209(in Chinese). doi: 10.3969/j.issn.1000-6923.2018.01.024
[29] 林晓璇, 孔青青, 曾泳钦, 等. 酮洛芬在臭氧作用下的降解机制、产物及毒性 [J]. 环境化学, 2018, 37(5): 1063-1070. LIN X X, KONG Q Q, ZENG Y Q, et al. Study on mechanism, intermediates and toxicity of ketoprofen degradation by ozone [J]. Environmental Chemistry, 2018, 37(5): 1063-1070(in Chinese).