-
垃圾焚烧飞灰(以下简称“飞灰”)和纳滤膜浓缩液均是生活垃圾无害化处理过程中产生的二次污染物,两者的无害化处置和资源化利用已成为当前环境主管部门需要迫切解决的难题. 飞灰通常含有高浸出浓度的重金属及痕量二噁英等污染物[1],已被列为危险废物. 飞灰若处置不当,会对环境和人体健康造成潜在危害[2-3]. 目前,我国飞灰主要处置方式是经过固化稳定化进入生活垃圾填埋场填埋,但重金属仍存在再度浸出的风险[4-5],而且北京、上海、江苏、浙江等经济发达省市诸多填埋场将面临封场,飞灰填埋面临着比较严峻的形势[6]. 而国内比较成熟的利用方式是水泥窑协同处置[7-8],但处置量有限,满足不了大量飞灰的消纳需求.
纳滤膜浓缩液是生活垃圾渗滤液膜法处理产生的高浓废水,其具有含盐量高、难降解有机物多、可生化性差等特点,难以生化处理[9-10]. 目前,纳滤膜浓缩液主要回灌生活垃圾填埋场[11],而深度处理技术包括高级氧化法[12]和蒸发[13]等,但这些技术的工业化应用多不能稳定运行,且产生二次固体废物也较难得到妥善处置,环境安全隐患仍较大. 鉴于此,本课题组利用飞灰比表面积大、吸附截留性能好的特性,结合热处理方法,提出了飞灰与纳滤膜浓缩液淋滤飞灰协同处置模式,通过协同处置去除纳滤膜浓缩液的色度、难生化降解有机污染物等特征污染物,实现了纳滤膜浓缩液从目前技术工艺“难处置的高浓度有机废水”变成“可处置的高盐废水”,同时去除了飞灰中可溶性氯盐,淋滤灰渣可经热处理后实现无害化与资源化利用[14]. 目前,国内外关于飞灰高温热处理过程中重金属的固化与挥发机制的研究报道很多[15-16],但关于纳滤膜浓缩液淋滤灰渣热处理过程中重金属的迁移特性尚无报道. 由于飞灰经纳滤膜浓缩液淋滤后去除了其中的Cl−,但增加了SO42−和PO43−等,可能影响后续热处理过程中重金属的迁移化特性.
飞灰中Pb含量通常较高,是一种典型的重金属,对人体会造成致癌健康风险[17]. 本课题组[18]前期研究表明,飞灰中Pb主要为PbO,少量以PbCl2形式存在,这些Pb在后续的热处理过程较易挥发. 孟棒棒[19]对膜浓缩液淋滤飞灰后灰渣进行热处理时发现,温度是影响重金属挥发率的重要因素,热处理温度高于800℃时,Pb的浸出浓度达到生活垃圾填埋场污染控制标准(GB16889-2008)标准限值要求,但未对热处理过程中Pb的迁移转化机理进行深入探究. 为了解纳滤膜浓缩液淋滤对飞灰中重金属存在以及后续热处理过程中迁移转化的影响,本研究以Pb为例,探讨了淋滤过程、以及后续热处理不同温度下Pb的存在形态以及迁移转化特性,以期为探究飞灰协同处置纳滤膜浓缩液的可行性提供科学依据.
焚烧飞灰在纳滤膜浓缩液淋滤及后续热处理中Pb的迁移转化
Migration and transformation of Pb in nanofiltration membrane leaching and incineration fly ash during heat treatment
-
摘要: 探究了纳滤膜浓缩液淋滤焚烧飞灰过程及淋滤灰渣在400—1000 ℃热处理过程中Pb的迁移转化特性. 结果表明,淋滤过程中飞灰中大部分氯盐被溶出,有新的矿物相Pb2(SO4)O出现. 后续的热处理中,在400—1000 ℃过程中Pb2(SO4)O分解成PbSO4,然后同Pb的磷酸盐稳定存在于灰渣中,碱式碳酸盐在400 ℃下完全分解. 当温度达到800 ℃以上,PbSiO3含量随着温度升高逐渐降低,生成了Ca2PbO4且生成量随着温度的升高而逐渐增大.Abstract: The leaching and incineration of fly ash from concentrated solution of nanofiltration membrane and the migration and transformation characteristics of Pb in leached ash during 400-1000℃ heat treatment were studied. The results showed that most of the chlorine salts in the fly ash were leached out during the leaching process, and a new mineral phase Pb2(SO4)O appeared. In the subsequent heat treatment, Pb2(SO4)O decomposed into PbSO4 at the temperature of 400—1000℃, and then the phosphate with Pb existed stably in the ash , and the alkali carbonate decomposed completely at 400℃. When the temperature reached above 800℃, the PbSiO3 content gradually decreased with the increase of temperature, and Ca2PbO4 was generated, and the amount generated gradually increased with the increase of temperature.
-
表 1 飞灰主要化学成分
Table 1. Main chemical compositions of MSWI fly ash and leached fly ash
主要成分
Ingredient含量/ %
Content主要成分
Ingredient含量/ %
ContentCaO 45.68±1.26 SiO2 2.72±0.19 Cl 22.75±0.28 ZnO 0.85±0.02 Na2O 12.17±0.12 Al2O3 0.81±0.10 SO3 6.16±0.11 P2O5 0.40±0.12 K2O 5.20±0.37 PbO 0.12±0.02 表 2 纳滤膜浓缩液水质参数(mg·L−1)
Table 2. Water quality parameters of nanofiltration membrane (mg·L−1)
污染物指标
Pollutant index化学需氧量
Chemical oxygen demand生化需氧量
Biochemical oxygen demand氨氮
Ammonia nitrogenCl− SO42− PO42− 纳滤膜浓缩液 2490±60 473±28 191±12 3420±38 249±18 5.88±0.37 表 3 淋滤前后飞灰主要化学成分(%)
Table 3. Main chemical constituents of fly ash before and after leaching
固体样品
Solid samplesCaO Cl SO3 SiO2 PbO P2O5 飞灰(加入PbO) 45.14±0.86 22.48±0.30 6.09±0.20 2.69±0.24 1.30±0.03 0.40±0.07 淋滤灰渣 33.63±0.56 0.40±0.08 2.39±0.23 1.52±0.05 27.36±0.22 0.19±0.08 表 4 淋滤前后纳滤膜浓缩液中主要离子指标
Table 4. Main ion indexes in nanofiltration membrane before and after leaching
液体样品
Liquid samplespH Cl-/(mg·L−1) SO42-/(mg·L−1) PO42-/(mg·L−1) 纳滤膜浓缩液 7.1±0.1 3.4×103±38.2 2.5×102±18.5 5.9±0.4 淋出液 13.5±0.1 3.2×105±1980.3 3.4×103±153.6 0.6×10−2±0.0 表 5 吉布斯反应自由能ΔG(kJ·mol−1)
Table 5. Gibbs reaction free energy energyΔG (kJ·mol−1)
温度/℃
Temperature式(3) 式(4) 式(5) 式(6) 400 446.4 −12.6 454.0 −16.1 600 340.8 −39.6 447.5 −16.2 800 238.2 −64.4 435.8 −17.5 1000 138.5 −89.3 412.5 −21.3 -
[1] 杨凤玲, 李鹏飞, 叶泽甫, 等. 城市生活垃圾焚烧飞灰组成特性及重金属熔融固化处理技术研究进展 [J]. 洁净煤技术, 2021, 27(1): 169-180. doi: 10.13226/j.issn.1006-6772.20052801 YANG F L, LI P F, YE Z F, et al. Study progress on the composition characteristics of fly ash from municipal solid waste incineration and treatment technology of heavy metal melting and solidification [J]. Clean Coal Technology, 2021, 27(1): 169-180(in Chinese). doi: 10.13226/j.issn.1006-6772.20052801
[2] HUBER F, LANER D, FELLNER J. Comparative life cycle assessment of MSWI fly ash treatment and disposal [J]. Waste Management, 2018, 73: 392-403. doi: 10.1016/j.wasman.2017.06.004 [3] SHARIFIKOLOUEI E, BAINO F, SALVO M, et al. Vitrification of municipal solid waste incineration fly ash: An approach to find the successful batch compositions [J]. Ceramics International, 2021, 47(6): 7738-7744. doi: 10.1016/j.ceramint.2020.11.118 [4] LIU Z Y, YUE Y, LU M, et al. Comprehension of heavy metal stability in municipal solid waste incineration fly ash with its compositional variety: A quick prediction case of leaching potential [J]. Waste Management, 2019, 84: 329-339. doi: 10.1016/j.wasman.2018.11.049 [5] 何品晶, 吴长淋, 章骅, 等. 生活垃圾焚烧飞灰及其稳定化产物的长期浸出行为 [J]. 环境化学, 2008, 27(6): 786-790. doi: 10.3321/j.issn:0254-6108.2008.06.018 HE P J, WU C L, ZHANG H, et al. The long-term leaching behavior of air pollution control residues and its treatment products [J]. Environmental Chemistry, 2008, 27(6): 786-790(in Chinese). doi: 10.3321/j.issn:0254-6108.2008.06.018
[6] HE H J, WU T, WANG X G, et al. Study on compressibility and settlement of a landfill with aged municipal solid waste: A case study in Taizhou [J]. Sustainability, 2021, 13(9): 4831. doi: 10.3390/su13094831 [7] 田书磊, 王琪, 汪群慧, 等. 垃圾焚烧飞灰熔融过程中重金属固化特性 [J]. 哈尔滨工业大学学报, 2008, 40(10): 1576-1580. doi: 10.3321/j.issn:0367-6234.2008.10.014 TIAN S L, WANG Q, WANG Q H, et al. Characterics of heavy metals during melting and solidification of MSWI fly ash [J]. Journal of Harbin Institute of Technology, 2008, 40(10): 1576-1580(in Chinese). doi: 10.3321/j.issn:0367-6234.2008.10.014
[8] WU K, SHI H S, de SCHUTTER G, et al. Preparation of alinite cement from municipal solid waste incineration fly ash [J]. Cement and Concrete Composites, 2012, 34(3): 322-327. doi: 10.1016/j.cemconcomp.2011.11.016 [9] 徐昌文, 王声东. 垃圾渗滤液及膜滤浓缩液处理技术探讨与分析 [J]. 环境与可持续发展, 2020, 45(5): 72-75. doi: 10.19758/j.cnki.issn1673-288x.202005072 XU C W, WANG S D. Discussion and analysis on treatment technology of leachate and membrane filtration concentrated solution [J]. Environment and Sustainable Development, 2020, 45(5): 72-75(in Chinese). doi: 10.19758/j.cnki.issn1673-288x.202005072
[10] 张睿涵. 阴极电Fenton法处理垃圾渗滤液浓缩液的研究及能耗评估[D]. 南宁: 广西大学, 2016: 2-11. ZHANG R H. Energy consumption evaluation of landfill leachate disposal using electro-Fenton[D]. Nanning: Guangxi University, 2016: 2-11(in Chinese).
[11] 王晓青, 赵成云, 罗竞红. 回灌法处理反渗透浓缩液的试验研究 [J]. 环境科技, 2015, 28(4): 18-21. doi: 10.3969/j.issn.1674-4829.2015.04.004 WANG X Q, ZHAO C Y, LUO J H. Study on pilot experiment of recirculation treatment of concentrated liquor produced by reverse osmosis [J]. Environmental Science and Technology, 2015, 28(4): 18-21(in Chinese). doi: 10.3969/j.issn.1674-4829.2015.04.004
[12] JIA C Z, WANG Y X, ZHANG C X, et al. UV-TiO2 photocatalytic degradation of landfill leachate [J]. Water, Air, & Soil Pollution, 2011, 217(1/2/3/4): 375-385. [13] 王东梅, 刘丹, 龚正君, 等. Fenton氧化-絮凝-吸附法处理垃圾渗滤液反渗透浓缩液 [J]. 科学技术与工程, 2013, 13(18): 5423-5426. doi: 10.3969/j.issn.1671-1815.2013.18.065 WANG D M, LIU D, GONG Z J, et al. Treatment of landfill leachate reverse osmosis concentrate by Fenton oxidation-coagulation-adsorption [J]. Science Technology and Engineering, 2013, 13(18): 5423-5426(in Chinese). doi: 10.3969/j.issn.1671-1815.2013.18.065
[14] 孟棒棒, 田书磊, 刘宏博, 等. 膜浓缩液淋滤飞灰后灰渣重金属热处理特性分析 [J]. 环境工程学报, 2019, 13(4): 992-999. MENG B B, TIAN S L, LIU H B, et al. Analysis on heat treatment of heavy metal in residues from fly ash leaching process by membrane concentrated leachate [J]. Chinese Journal of Environmental Engineering, 2019, 13(4): 992-999(in Chinese).
[15] 王琛, 许继云, 邵宁宁, 等. 危废焚烧过程中二噁英和颗粒物的生成机理以及重金属迁移特征探究 [J]. 环境卫生工程, 2020, 28(4): 111-112. WANG C, XU J Y, SHAO N N, et al. A field study of polychlorinated dibenzo-p-dioxins and dibenzofurans formation mechanism in a hazardous waste incinerator: Emission reduction strategies [J]. Environmental Sanitation Engineering, 2020, 28(4): 111-112(in Chinese).
[16] TIAN X, RAO F, LI C X, et al. Solidification of municipal solid waste incineration fly ash and immobilization of heavy metals using waste glass in alkaline activation system [J]. Chemosphere, 2021, 283: 131240. doi: 10.1016/j.chemosphere.2021.131240 [17] 刘丽君, 韩静磊, 钱益斌, 等. 利用靶器官毒性剂量法(TTD)和证据权重分析法(WOE)评估固化飞灰中重金属非致癌健康风险 [J]. 环境化学, 2019, 38(5): 1014-1020. doi: 10.7524/j.issn.0254-6108.2018062002 LIU L J, HAN J L, QIAN Y B, et al. Assessment of heavy metal non-carcinogenic health risk in solidified fly ash using TTD and WOE methods [J]. Environmental Chemistry, 2019, 38(5): 1014-1020(in Chinese). doi: 10.7524/j.issn.0254-6108.2018062002
[18] TIAN S L, ZHU Y C, MENG B B, et al. Chemical speciation of lead in secondary fly ash using X-ray absorption spectroscopy [J]. Chemosphere, 2018, 197: 362-366. doi: 10.1016/j.chemosphere.2018.01.026 [19] 孟棒棒. 利用生活垃圾焚烧飞灰协同处理膜浓缩液的研究[D]. 哈尔滨: 哈尔滨理工大学, 2018: 55-57. MENG B B. Study on the synergistic treatment of membrane concentrated leachate by MSWI fly ash[D]. Harbin: Harbin University of Science and Technology, 2018: 55-57 (in Chinese)
[20] 中华人民共和国环境保护部. 固体废物 金属元素的测定 电感耦合等离子体质谱法: HJ 766—2015[S]. 北京: 中国环境科学出版社, 2015. Ministry of Environmental Protection of the People's Republic of China. Solid Waste-Determination of metals-Inductively coupled plasma mass spectrometry (ICP-MS): HJ 766—2015[S]. Beijing: China Environment Science Press, 2015(in Chinese).
[21] 龚勋. 典型西部粉煤灰中重金属元素淋滤特性研究[D]. 武汉: 华中科技大学, 2010: 82. GONG X. Leaching characteristics of heavy metal in the coal ash from West China[D]. Wuhan: Huazhong University of Science and Technology, 2010: 82 (in Chinese)
[22] 田书磊. 垃圾焚烧飞灰重金属热分离工艺及挥发特性研究[D]. 哈尔滨: 哈尔滨工业大学, 2007: 68-71. TIAN S L. Thermal-separation process and evaporation mechanism of heavy metal from MSWI fly ash[D]. Harbin: Harbin Institute of Technology, 2007: 68-71 (in Chinese)
[23] LU Q, ZHOU X Y, WU Y W, et al. Migration and transformation of lead species over CaO surface in municipal solid waste incineration fly Ash: A DFT study [J]. Waste Management, 2021, 120: 59-67. doi: 10.1016/j.wasman.2020.11.011 [24] 孙立, 吴新, 刘道洁, 等. 基于硅基的垃圾焚烧飞灰中温热处理重金属稳固化实验 [J]. 化工进展, 2017, 36(9): 3514-3522. doi: 10.16085/j.issn.1000-6613.2017-0141 SUN L, WU X, LIU D J, et al. Stabilization of heavy metals in municipal solid waste incineration fly ash using thermal treatment with silica-based material [J]. Chemical Industry and Engineering Progress, 2017, 36(9): 3514-3522(in Chinese). doi: 10.16085/j.issn.1000-6613.2017-0141
[25] 张芝昆. 油页岩复合灰制备微晶玻璃及其固化垃圾焚烧飞灰的研究[D]. 大连: 大连理工大学, 2016: 37-40. ZHANG Z K. Preparation of glass-ceramics and solidification of solid waste incineration fly ash using oil shale fly ash-based composite ashes[D]. Dalian: Dalian University of Technology, 2016: 37-40 (in Chinese)
[26] YANG Z H, LIN Q, LU S C, et al. Effect of CaO/SiO2 ratio on the preparation and crystallization of glass-ceramics from copper slag [J]. Ceramics International, 2014, 40(5): 7297-7305. doi: 10.1016/j.ceramint.2013.12.071 [27] LI Y, TASKINEN P, WANG Y J, et al. PbSO4 reduction mechanism and gas composition at 600–1000℃ [J]. JOM, 2021, 73(3): 881-891. doi: 10.1007/s11837-020-04551-4 [28] 刘敬勇, 孙水裕, 陈涛, 等. 污泥焚烧a过程中Pb的迁移行为及吸附脱除 [J]. 中国环境科学, 2014, 34(2): 466-477. LIU J Y, SUN S Y, CHEN T, et al. Migration behavior of Pb and its vaporization control during sewage sludge incineration process [J]. China Environmental Science, 2014, 34(2): 466-477(in Chinese).