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土壤是人类生存与发展不可或缺的自然资源[1]。2014年发布的《全国土壤污染状况调查公报》显示,全国土壤污染总超标率为16.1%。其中,镉(Cd)的超标点位数达到7.0%,是超标率最高的金属污染物[2]。Cd的生物毒性强,积累容易但难去除,是毒性较大的重金属之一[3],亦为诸多研究者重点关注的土壤污染物。目前,土壤重金属污染的修复技术包括化学淋洗、生物修复、稳定化等[4]。稳定化是一种较为成熟的污染土壤修复技术,一般指通过物理/化学吸附、水化、沉淀等作用固定土壤中的有毒元素[5]。稳定化修复也是较为广泛的Cd污染土壤修复方法之一,具有处理时间短、应用范围广、成本相对较低等优点[6]。硅酸盐材料是常用的稳定化材料,其水化反应能显著提高系统pH,并有利于重金属转化为溶解度较低的氢氧化物或碳酸盐,其水化产物也能较好地吸附重金属离子[7]。然而,因其对污染物的包容量差、易膨胀[8],硅酸盐材料对某些污染物的稳定化效果欠佳,亟需探索新的稳定化材料。
铝酸盐材料是一种胶凝材料,具有硬化速度快、抗腐蚀能力强、耐高温等特点[9]。在环境领域,已有关于铝酸盐材料用于固体废物固化处理的研究,并取得了满意的效果[10]。如LIANG等[11]使用铝酸盐材料固化处理城市垃圾焚烧飞灰,使飞灰中铅和锌的浸出质量浓度分别降低了96.2%和85.6%。但目前尚无铝酸盐材料用于稳定化修复重金属污染土壤的研究。本研究以Cd为目标污染物,通过室内模拟土壤稳定化实验,评估铝酸盐材料对Cd污染土壤的修复效果,并通过技术分析探讨铝酸盐材料稳定化Cd的机制,以期为土壤Cd污染修复提供参考。
铝酸盐材料对镉污染土壤的稳定化修复及其机理
Stabilization and remediation of Cadmium contaminated soil by Aluminate and its mechanisms
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摘要: 为研究铝酸盐材料对于修复Cd污染土壤的可行性,以常见的硅酸盐材料为参照,比较了两者对土壤中Cd的稳定化效果,并对相关反应机制进行了讨论。结果表明:当土壤中Cd的质量分数为54.6 mg·kg−1时,铝酸盐和硅酸盐材料使Cd的7 d浸出质量浓度分别降低58.07%~77.75%和63.46%~93.02%,180 d浸出质量浓度分别降低28.72%~79.23%和41.08%~86.63%;当土壤中Cd的质量分数为2 940.03 mg·kg−1时,铝酸盐和硅酸盐材料使Cd的7 d浸出质量浓度分别降低76.97%~93.15%和19.05%~94.38%,180 d浸出质量浓度分别降低56.56%~88.87%和-32.68%~49.79%。这说明铝酸盐材料对土壤中Cd的稳定化效果优于硅酸盐材料。在CdCl2溶液中(94.02 mg·L−1),铝酸盐和硅酸盐材料分别使Cd质量浓度降低了99.92%~99.93%和99.68%~99.92%,并使pH分别增大了6.56~6.81和7.01~7.69。通过SEM-EDS、FTIR、XRD和XPS等分析手段发现,铝酸盐材料可通过水化反应生成Ca—Si—H和Ca—Al—Si—H凝胶,以实现对Cd的物理包裹和吸附,并可通过使pH增大而生成Cd(OH)2、CdO或CdCO3沉淀,进而实现了对Cd的稳定化。本研究表明铝酸盐材料较硅酸盐材料对Cd的稳定化更为高效且长效,可为Cd污染土壤修复提供参考。Abstract: In order to explore the feasibility of aluminate in cadmium contaminated soil remediation, the stabilization effects of aluminate material on cadmium polluted soil were compared with traditional silicate material, and the related reacion mechanism was expounded. The results showed that when the mass fraction of Cd was 54.6 mg·kg−1, the leaching mass concentration of Cd at 7 d decreased by 58.07%~77.75% and 63.46%~93.02% with aluminate and silicate materails, respectively, and the leaching mass concentration at 180 decreased by 28.72%~79.23% and 41.08%~86.63%, respectively.. When the mass fraction of Cd was 2 940.03 mg·kg−1, the leaching mass concentration of Cd at 7 d decreased by 76.97%~93.15% and 19.05%~94.38% with aluminate and silicate materails, respectively, and the leaching mass concentration of Cd at 180d decreased by 56.56%~88.87% and −32.68%~49.79%, respectively. These results indicated that aluminate material was more efficient in stabilization of cadmium in soil than silicate material. In CdCl2 solution (94.02 mg·L−1), aluminate and silicate reduced Cd concentration by 99.92%~99.93% and 99.68%~99.92%, respectively, and increased pH by 6.56~6.81 and 7.01~7.69, respectively. Through SEM-EDS, FTIR, XRD and XPS analysis, it was found that aluminate could form Ca—Si—H and Ca—Al—Si—H gels through hydration reaction to achieve physical encapsulating and adsorption of Cd. In addition, aluminate could also increase pH to generate Cd(OH)2, CdO or CdCO3 to realize the stabization of Cd. In conclusion, aluminate was more efficient and long-term in stabilization of cadmium than silicate, which can provide reference for the remediation of cadmium-contaminated soil.
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Key words:
- aluminate /
- cadmium /
- soil remediation /
- stabilization
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表 1 稳定化材料的元素组成
Table 1. Elemental compositions of stabilized materials
% 材料类型 CaO Al2O3 SiO2 Fe2O3 Na2O K2O 硅酸盐材料 62.1 3.9 22.5 3.21 0.46 0.30 铝酸盐材料 33.5 51.1 6.7 2.4 0.32 0.00 表 2 实验设置
Table 2. Experiment settings
% 处理 硅酸盐材料的质量分数 铝酸盐材料的质量分数 CK 0 0 SN-1 1 0 SN-3 3 0 SN-5 5 0 AN-1 0 1 AN-3 0 3 AN-5 0 5 表 3 实验设置
Table 3. Experiment settings
% 处理 硅酸盐材料的质量分数 铝酸盐材料的质量分数 CK 0 0 SN0.1 0.1 0 SN0.5 0.5 0 SN1 1 0 AN0.1 0 0.1 AN0.5 0 0.5 AN1 0 1 -
[1] 廖晓勇, 崇忠义, 阎秀兰, 等. 城市工业污染场地: 中国环境修复领域的新课题[J]. 环境科学, 2011, 32(3): 784-794. [2] 环境保护部, 国土资源部. 全国土壤污染状况调查公报[R/OL]. 2014. http://www.mee.gov.cn/gkml/sthjbgw/qt/201404/t20140417_270670.htm. [3] FOWLER B A. Monitoring of human populations for early markers of cadmium toxicity: A review[J]. Toxicology and Applied Pharmacology, 2009, 238(3): 294-300. doi: 10.1016/j.taap.2009.05.004 [4] 曹心德, 魏晓欣, 代革联, 等. 土壤重金属复合污染及其化学钝化修复技术研究进展[J]. 环境工程学报, 2011, 5(7): 1441-1453. [5] WANG F, XU J, YIN H L, et al. Sustainable stabilization/solidification of the Pb, Zn, and Cd contaminated soil by red mud-derived binders[J]. Environmental Pollution, 2021, 284: 117-118. [6] SHEN Z T, JIN F, O'CONNOR D, et al. Solidification/Stabilization for Soil Remediation: An Old Technology with New Vitality.[J]. Environmental science & technology, 2019, 53(20): 11615-11617. [7] 张长波, 罗启仕, 付融冰, 等. 污染土壤的固化/稳定化处理技术研究进展[J]. 土壤, 2009, 41(1): 8-15. [8] POON C S, QIAO X C, CHEESEMAN C R. Applications of rejected fly ash in stabilization and solidification processes[J]. London:Taylor and Francis, 2005: 63-68. [9] 王中平, 陈钰婷, 彭相, 等. 高温与碳化对铝酸盐水泥水化产物氯离子结合性能影响[J/OL]. 建筑材料学报: 1-12[2021-08-11]. https://kns.cnki.net/kcms/detail/31.1764.TU.20210802.1747.006.html.请确定是否已经见刊(未) [10] NAVARRO-BLASCO I, DURAN A, SIRERA R, et al. Solidification/stabilization of toxic metals in calcium aluminate cement matrices[J]. Journal of Hazardous Materials, 2013, 260(1): 89-103. [11] LIANG C, WANG Y S, WANG L, et al. Stabilisation/solidification of municipal solid waste incineration fly ash by phosphate-enhanced calcium aluminate cement[J]. Journal of Hazardous Materials, 2020, 408: 124404. [12] 自然资源部, 水利部. 地下水质量标准: GB/T 14848-2017[S/OL]. 2017. http://std.samr.gov.cn/gb/search/gbDetailed?id=71F772D81F67D3A7E05397BE0A0AB82A. [13] LI X Z, JIA R, LU X Z, et al. The use of mercapto-modified palygorskite prevents the bioaccumulation of cadmium in wheat[J]. Journal of Hazardous Materials, 2021, 417: 125917. doi: 10.1016/j.jhazmat.2021.125917 [14] YANG P, CHEN H J, FAN H Y, et al. Phosphorus supply alters the root metabolism of Chinese flowering cabbage ( Brassica campestris L. ssp. chinensis var. utilis Tsenet Lee) and the mobilization of Cd bound to lepidocrocite in soil[J]. Environmental and Experimental Botany, 2019, 167: 1-8. [15] PYLE S M, NOCERINO J M, DEMING S N, et al. Comparison of AAS, ICP-AES, PSA, and XRF in Determining Lead and Cadmium in Soil[J]. Environmental science & technology, 1996, 30(1): 204-213. [16] 生态环境部. 固体废物浸出毒性浸出方法 水平振荡法: HJ 557—2010[S]. 北京: 中国环境科学出版社, 2010. [17] 叶兴银, 张卫, 龙精华, 等. 人工纳米颗粒输入对稻田土壤Cd形态转化及生物有效性的影响[J]. 环境工程学报, 2018, 12(12): 3426-3432. [18] HAN J, XU Y M, LIANG X F, et al. Sorption stability and mechanism exploration of Palygorskite as immobilization agent for Cd in polluted soil[J]. Water, Air, & Soil Pollution, 2014, 225(10): 1-13. [19] HE S R, LI Y T, WENG L P, et al. Competitive adsorption of Cd2+, Pb2+ and N2+ onto F3+-modified argillaceous limestone: Influence of pH, ionic strength and natural organic matters[J]. Science of the Total Environment, 2018, 637-638: 69-78. doi: 10.1016/j.scitotenv.2018.04.300 [20] 朱洪波, 韩亚倩, 张祎璐, 等. 硅酸盐白水泥石面层加速碳化程度与微观结构[J/OL]. 建筑材料学报: 1-8[2022-01-08]. http://kns.cnki.net/kcms/detail/31.1764.TU.20211227.1636.002.html. [21] 蒋宁俊, 杜延军, 刘松玉, 等. 酸雨入渗对水泥固化铅污染土淋滤特性的影响研究[J]. 岩土工程学报, 2013, 35(4): 739-744. [22] MARTı́NEZ C. E, MOTTO H. L. Solubility of lead, zinc and copper added to mineral soils[J]. Environmental Pollution, 2000, 107(1): 153-158. doi: 10.1016/S0269-7491(99)00111-6 [23] MAHAR A, WANG P, ALI A, et al. Impact of CaO, fly ash, sulfur and Na2S on the (im)mobilization and phytoavailability of Cd, Cu and Pb in contaminated soil[J]. Ecotoxicology and Environmental Safety, 2016, 134(Pt 1): 116-123. [24] 齐一谨, 彭熙, 徐中慧, 等. 机械力活化固硫灰固化处理生活垃圾焚烧飞灰[J]. 环境工程学报, 2017, 11(4): 2469-2474. [25] POMIÈS M P, LEQUEUX N, BOCH P. Speciation of cadmium in cement[J]. Cement and Concrete Research, 2001, 31(4): 571-576. doi: 10.1016/S0008-8846(00)00477-4 [26] GINEYS N, AOUAD G, DAMIDOT D. Managing trace elements in Portland cement-Part I: Interactions between cement paste and heavy metals added during mixing as soluble salts[J]. Cement and Concrete Composites, 2010, 32(8): 563-570. doi: 10.1016/j.cemconcomp.2010.06.002 [27] HONG S Y, GLASSER F P. Alkali sorption by C-S-H and C-A-S-H gels[J]. Cement and Concrete Research, 2002, 32(7): 1101-1111. doi: 10.1016/S0008-8846(02)00753-6 [28] 宋学锋, 邓倩倩. 不同养护温度下铝酸盐水泥抑制碱矿渣早期泛霜的研究[J]. 硅酸盐通报, 2018, 37(12): 4018-4021. [29] ZHOU H, LV W X, JIAO J W, et al. Effect of Li+ on the composition and morphology of C-A-S-H[J]. Construction and Building Materials, 2021, 301: 123982. doi: 10.1016/j.conbuildmat.2021.123982 [30] 吕浩阳, 费杨, 王爱勤, 等. 甘肃白银东大沟铅锌镉复合污染场地水泥固化稳定化原位修复[J]. 环境科学, 2017, 38(9): 3897-3906. [31] GOUGAR M L D, SCHEETZ B E, ROY D M. Ettringite and C-S-H Portland cement phases for waste ion immobilization: A review[J]. Waste Management, 1996, 16(4): 295-303. doi: 10.1016/S0956-053X(96)00072-4 [32] 张集发. 片状α-Al2O3粉体的合成与研究[D]. 广州: 华南理工大学, 2016. [33] LIANG X F, HAN J, XU Y M, et al. Sorption of Cd2+on mercapto and amino functionalized palygorskite[J]. Applied Surface Science, 2014, 322: 194-201. doi: 10.1016/j.apsusc.2014.10.092