-
铬(Cr)及其化合物常用于采矿、电镀等行业中,而在水体中主要以Cr(Ⅲ)和Cr(Ⅵ)存在[1-2]。 相较于Cr(Ⅲ),Cr(Ⅵ)具有可吸附性低、生物毒性强的特点,如未经处理排放到水体中,会严重威胁我国水生态环境和人民生命健康[3-4]。目前,关于Cr(Ⅵ)的处理方法主要包括物理法[5-6]和化学法[7-8]。物理法主要是采用吸附材料(活性炭、生物炭、高分子聚合物)将Cr(Ⅵ)从水相转移至吸附材料中,该方法虽具有操作方便、材料廉价易得等优势,但却存在二次污染风险[9],需进行二次处理。而化学法主要是通过加入一定数量的还原剂,从而将Cr(Ⅵ)还原转化为毒性相对较低的Cr(Ⅲ),再通过调节水体的pH值,使Cr(Ⅲ)生成沉淀物质,实现水体和Cr(Ⅲ)的分离,达到去除Cr(Ⅵ)的目的,该方法是目前应用最为广泛的方法。
零价铁(Fe)具有还原性高、环境友好等优势,常用于水体重金属去除,但也存在颗粒易聚集、表面易氧化等缺点[10-11]。四氧化三铁(Fe3O4)是立方反尖晶石,由O2-与Fe2+、Fe3+亚晶格紧密堆积组成。其中,Fe(Ⅲ)([Fe3+]tetra)占据四面体阳离子位,Fe(Ⅱ)([Fe2+]octa)和Fe(Ⅲ)([Fe3+]octa)占据正八面体阳离子位,这使得Fe3O4电子可自由转移[12]。近几年来,Fe/Fe3O4被广泛应用于污染物催化氧化、机械脱卤过程中。一方面Fe可促进Fe(Ⅱ)/Fe(Ⅲ)的循环;另一方面Fe3O4可促进将电子传递给污染物的过程。在基于过一硫酸盐的催化氧化过程中,与Fe和Fe3O4相比,Fe/Fe3O4具有更高的催化效率和活性物种产率[13]。
机械球磨是利用磨球和物料碰撞摩擦,使得反应活化能降低、有利于固体污染物的降解。在机械球磨脱卤过程中,Fe/Fe3O4作为助磨剂可高效去除六氯苯、全氟辛烷磺酸等污染物[14-16],且在Fe/Fe3O4质量为3:7时效果最佳。由于Fe/Fe3O4具有较高的电子传递效率,将其作为助磨剂时可降低物料比(即降解单位质量污染物所需的助磨剂量),但仍面临着助磨剂尾料资源化利用的难题[16-21]。然而,研磨的Fe/Fe3O4具有良好的Cr(Ⅵ)还原性能。目前,有研究报道手动研磨的Fe和Fe3O4混合物可将Cr(Ⅵ)还原为Cr(Ⅲ),究其原因是Fe和[Fe3+]octa发生反应生成[Fe2+]octa[8]。因此,将机械球磨后的Fe/Fe3O4尾料用于Cr(Ⅵ)的还原去除,是促进尾料资源化利用的有效方式。
因此,本研究基于Fe/Fe3O4尾料资源化利用和高性能Cr(Ⅵ)还原材料开发的双重考虑,通过球磨模拟制备Fe/Fe3O4材料,研究球磨Fe/Fe3O4材料对Cr(Ⅵ)的还原性能以及其强化机理;探究最佳球磨条件(球磨氛围和时间)及还原条件(球磨材料投加量和初始pH),为研究Fe/Fe3O4尾料资源化利用以及机械球磨Fe/Fe3O4对Cr(Ⅵ)还原性能的影响提供重要数据支撑。
机械球磨强化铁/四氧化三铁对Cr(Ⅵ)的还原性能
Performance enhancement of Cr(Ⅵ) reduction for Fe/Fe3O4 by mechanical milling
-
摘要: Fe/Fe3O4作为机械球磨助磨剂可高效去除含卤污染物,但也面临着助磨剂尾料资源化利用的难题。机械球磨后的Fe/Fe3O4尾料具有良好的Cr(Ⅵ)还原性能。本研究基于尾料资源化利用和高性能材料开发的双重考虑,通过球磨模拟制备具有高Cr(Ⅵ)还原性能的Fe/Fe3O4材料。结果表明,机械球磨强化了Fe/Fe3O4材料的Cr(Ⅵ)还原性能,Cr(Ⅵ)去除率由26.1%提升至91.3%。机械球磨主要是通过促进Fe(Ⅱ)的生成和Fe释放电子的传递强化Cr(Ⅵ)还原。采用球磨Fe/Fe3O4还原Cr(Ⅵ)时,Fe(Ⅱ)的高生成量说明机械球磨促进了Fe(Ⅱ)的生成,而Fe(Ⅲ) 的高生成量和pH的大幅上升说明Fe(Ⅱ)转化为Fe(Ⅲ)。利用邻菲啰啉淬灭Fe(Ⅱ),使得球磨Fe/Fe3O4材料对Cr(Ⅵ) 的去除率降至41.8%,这表明Fe(Ⅱ)对Cr(Ⅵ) 还原起主要作用。过量的氧气和过长的球磨时间可削弱球磨Fe/Fe3O4的Cr(Ⅵ)还原性能,最佳球磨条件为氮气氛围、球磨30 min;Cr(Ⅵ)去除效果与球磨Fe/Fe3O4投加量呈正相关,而与初始pH呈负相关。Abstract: Fe/Fe3O4 as an additive for mechanical milling can efficiently degrade halogenated pollutants, but the reutilization of additive tailing is a problem. The Fe/Fe3O4 tailing has a good performance on Cr(Ⅵ) reduction. In this study, the Fe/Fe3O4 material with high performance of Cr(Ⅵ) reduction was prepared by mechanical milling simulation based on the dual consideration of tailing reutilization and material development. The results show that mechanical milling enhanced the reduction performance of Fe/Fe3O4, and the removal ratio of Cr(Ⅵ) increased from 26.1% to 91.3%. The enhancement of mechanical milling was primarily through the promotion of Fe(Ⅱ) generation and transfer of Fe-released electrons. When the milled Fe/Fe3O4 was used for Cr(Ⅵ) reduction, the high formation of Fe(Ⅱ) implies that the mechanical milling promoted its yield, and the high generation of Fe(Ⅲ) and rise of pH indicate the conversion of Fe(Ⅱ) to Fe(Ⅲ). After the quenching of Fe(Ⅱ) by phenanthroline, the removal ratio of Cr(Ⅵ) by the milled Fe/Fe3O4 decreased to 41.8%, indicating that Fe(Ⅱ) played a major role in Cr(Ⅵ) reduction, and the mechanical milling enhanced the transfer of electrons released from Fe. Excessive oxygen and milling time weakened the reduction performance of the milled Fe/Fe3O4, and the optimum conditions were nitrogen atmosphere and a milling time of 30 min. The removal ratio of Cr(Ⅵ) was positively correlated with the dosage of the milled Fe/Fe3O4 material, while was negatively correlated with the initial pH.
-
Key words:
- Fe /
- Fe3O4 /
- mechanical milling /
- Cr(Ⅵ) /
- reduction enhancement
-
-
[1] 万仲豪, 李孟, 张倩. 间苯胺改性磁性壳聚糖对六价铬的还原-吸附协同作用机制研究[J]. 环境科学学报, 2018, 38(8): 3118-3126. [2] 张力, 赵勇胜. 六价铬污染模拟含水层的注入型黄原胶凝胶阻截屏障试验研究[J]. 水文地质工程地质, 2023, 50(2): 171-177. [3] 张进德, 田磊, 裴圣良. 矿山水土污染与防治对策研究[J]. 水文地质工程地质, 2021, 48(2): 157-163. [4] 徐衍忠, 秦绪娜, 刘祥红, 等. 铬污染及其生态效应[J]. 环境科学与技术, 2002, 25: 8-9. [5] LIU Z G, ZHANG F S, WU J Z. Characterization and application of chars produced from pinewood pyrolysis and hydrothermal treatment[J]. Fuel, 2010, 89(2): 510-514. doi: 10.1016/j.fuel.2009.08.042 [6] 陈园园, 井琦, 任仲宇. 改性硅藻土负载纳米零价铁去除六价铬[J]. 应用化工, 2020, 49(3): 541-544. [7] MALLICK S, DASH S S, PARIDA K M. Adsorption of hexavalent chromium on manganese nodule leached residue obtained from NH3-SO2 leaching[J]. Journal of Colloid Interface Science, 2006, 297(2): 419-425. doi: 10.1016/j.jcis.2005.11.001 [8] COELHO F D S, ARDISSON J D, MOURA F C, et al. Potential application of highly reactive Fe(0)/Fe3O4 composites for the reduction of Cr(Ⅵ) environmental contaminants[J]. Chemosphere, 2008, 71: 90-96. doi: 10.1016/j.chemosphere.2007.10.016 [9] 平松, 杨茸茸, 吴雷, 等. 改性多孔兰炭末吸附处理模拟含铬废水[J]. 环境工程, 2023, 41(2): 7-15. [10] LI J X, ZHANG X Y, SUN Y K, et al. Advances in sulfidation of zerovalent iron for water decontamination[J]. Environmental Science & Technology, 2017, 51(23): 13533-13544. [11] WEI K, LI H, GU H, et al. Strained zero-valent iron for highly efficient heavy metal removal[J]. Advanced Functional Materials, 2022, 32(26): 2200498. doi: 10.1002/adfm.202200498 [12] RITTER M, WEISS W. Fe3O4(Ⅲ) surface structure determined by LEED crystallography[J]. Surface Science, 1999, 432: 81-94. doi: 10.1016/S0039-6028(99)00518-X [13] HU J, CHEN H, DONG H Y, et al. Transformation of iopamidol and atrazine by peroxymonosulfate under catalysis of a composite iron corrosion product (Fe/Fe3O4): Electron transfer, active species and reaction pathways[J]. Journal of Hazardous Materials, 2021, 403: 123553. doi: 10.1016/j.jhazmat.2020.123553 [14] HU J, HUANG Z Y, YU J M, Highly-effective mechanochemical destruction of hexachloroethane and hexachlorobenzene with Fe/Fe3O4 mixture as a novel additive. Science of the Total Environment. 2019, 659: 578−586. [15] 张震, 陈飞勇, 刘汝鹏, 等. 基于响应曲面法优化的臭氧/过硫酸盐/四氧化三铁工艺对结晶紫的降解[J]. 环境工程学报, 2023, 17(7): 2192-2204. [16] HU J, QIU Y F, GU B, et al. Enhancement mechanism of magnetite on the ball-milling destruction of perfluoro- octane sulfonate by iron [J]. Environmental Pollution, 2023: 121014. [17] ZHANG W, WANG H Z, HUANG J, et al. Acceleration and mechanistic studies of the mechanochemical dechlorination of HCB with iron powder and quartz sand[J]. Chemical Engineering Journal, 2014, 239: 185-191. doi: 10.1016/j.cej.2013.11.018 [18] DENG S S, KANG S G, FENG N N, et al. Mechanochemical mechanism of rapid dechlorination of hexachloro -benzene[J]. Journal of Hazardous Materials, 2017, 333: 116-127. doi: 10.1016/j.jhazmat.2017.03.022 [19] 王文豪. 零价金属及其复合物去除废水中Cr(Ⅵ)的效能与机理[D]. 重庆: 重庆大学, 2022. [20] 张文秋, 史晓国, 刘伟鑫. 湿式球磨法机械化学合成FeS2工艺[J]. 材料科学与工程学报, 2023, 41(3): 502-508. [21] 胡俊, 章献钊, 姚蕾, 等. 活性炭共球磨强化铁/四氧化三铁的六价铬还原性能[J]. 环境科学学报, 2023, 43(10): 116-122. [22] AMBIKA S, DEVASENA M. , NAMBI I M, Synthesis, characterization and performance of high energy ball milled meso-scale zero valent iron in Fenton reaction[J]. Journal of Environmental Management, 2016, 181: 84-855. [23] GU Y, WANG B, HE F, Mechanochemically sulfidated microscale zero valent iron: pathways, kinetics, mechanism, and efficiency of trichloroethylene dechlorination [J]. Environmental Science & Technology, 2017, 51(21): 12653-12662. [24] SHAO Q Q, XU C H, WANG Y H, et al. Dynamic interactions between sulfidated zerovalent iron and dissolved oxygen: Mechanistic insights for enhanced chromate removal[J]. Water Research, 2018, 135: 322-330. doi: 10.1016/j.watres.2018.02.030 [25] WANG W H, HU B B, WANG C, et al. Cr(Ⅵ) removal by micron-scale iron-carbon composite induced by ball milling: The role of activated carbon[J]. Chemical Engineering Journal, 2020, 389: 122633. doi: 10.1016/j.cej.2019.122633 [26] GAN C, LIU Y G, TAN X F, et al. Effect of porous zinc-biochar nanocomposites on Cr(Ⅵ) adsorption from aqueous solution[J]. RSC Advances, 2015, 5(44): 35107-35115. doi: 10.1039/C5RA04416B