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我国工业生产以及日常生活中产生危险废物的量逐年增加,已对环境造成了极大影响[1-3]。我国半导体行业和集成电路行业每年都会产生大量污泥,这些污泥含有大量铜、镍等重金属[4]。含铜污泥的简单堆积会造成资源浪费,且其含有的重金属和有毒有害物质会随着雨水渗入到地下,对土壤和水体造成污染,继而对人群健康造成威胁[5-7]。研究发现,当人体内的铜过度积累后,会出现生理病变、发育停滞,甚至死亡的后果[8]。为响应危险废物资源化利用和国家碳达峰碳中和的发展要求,含铜污泥的合理处置问题愈发受到重视。
目前,我国对含铜污泥通常采用火法熔炼和集中填埋的处置方式。火法熔炼是通过还原法使污泥中的铜富集回收[9]。但是,含铜污泥铜含量太低,这与传统炼铜原料有较大差距,铜的提炼价值有限;同时,火法熔炼的工艺较为复杂,成本较高,提取重金属之后剩余的杂质还需要进一步处理。集中填埋的缺点是土地占有面积大,有较高的场地和施工成本,且污泥填埋并不能最终避免环境污染[10]。与上述2种方法比较,水泥窑协同处置技术因具有处置对象广、处置规模大、改造成本低、环保指标好等优点,是一种高效经济的处理固体废物的工艺方法[11-15]。水泥回转窑内温度最高可达1 600 ℃,物料在其中停留30 min,可以充分地焚烧固体废物[16-20]。同时,由于我国对水泥、混凝土等基建材料需求巨大,故水泥窑协同处置技术有很好的发展前景。目前,水泥窑协同处置重金属已经被广泛研究。NAVARRO等[21]对普通硅酸盐水泥固化Cu2+进行探索研究,发现Cu2+可被稳定的固化在熟料中。王培铭等[22]研究外掺CuO对熟料矿物相和水化性能的影响,发现掺入适量Cu2+促进C3S形成和C3S晶粒的成长,过量的Cu2+会延缓水化进程。兰明章[23]采用含重金属的危险工业废弃物配制生料烧制水泥熟料,发现掺入的重金属元素绝大部分可以固溶在熟料矿物中。伴随着我国半导体、集成电路行业的飞速发展,含铜污泥的产量增速加快,但目前还没有对含铜污泥行之有效的处置措施。
本研究拟利用水泥窑协同处置含铜污泥,开展含铜污泥的掺入对熟料性能及其中所含重金属对环境安全性的影响的研究。本研究在原始生料中掺入不同量含铜污泥烧制水泥熟料,通过X射线衍射分析(XRD)、电感耦合等离子体质谱(ICP-MS)、f-CaO测定、扫描电镜(SEM-EDS)和分相萃取等测试手段,探索含铜污泥的掺入对水泥熟料的煅烧温度和性能的影响、熟料中重金属的固化及在熟料中的分布情况,以及含铜污泥中重金属浸出浓度的影响。以期在水泥生产过程中更好处置含铜污泥提供参考。
水泥窑协同处置含铜污泥对水泥熟料性能及环境安全性的影响
Effect of Copper-containing sludge co-disposed by cement kiln on properties of cement clinker and its environmental safety
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摘要: 针对目前没有合理方法处置含铜污泥的问题,利用水泥窑协同处置技术对含铜污泥进行处置,以达到废物资源化的目的。通过掺入不同量的含铜污泥煅烧成水泥熟料,探讨了含铜污泥对硅酸盐水泥熟料性能及其中所含重金属的浸出对环境安全性的影响。结果表明,含铜污泥的加入明显降低了熟料的f-CaO质量分数,改善了水泥生料的易烧性。当含铜污泥掺量为4%及以下时,含铜污泥掺入会有效促进硅酸盐水泥的水化,使3、7和28 d抗压强度最高分别可达到49.85、46.85和65.8 MPa;当其掺量超过4%后,会明显抑制水泥的水化,劣化水泥水化程度,使其力学强度迅速降低。熟料各矿物相对重金属元素的固化具有选择性,含铜污泥中含量最多的Cu主要存在于中间相中,少数分布于硅酸盐相中;含铜污泥中的Cu离子可以有效固化在水泥熟料中,固化率最高可达87%。Cu离子在水泥净浆中的浸出浓度低于工业固体废弃物浸出毒性鉴别标准的规定指标,水泥窑协同处置含铜污泥在使用中不会对环境造成二次污染。本研究结果可为水泥窑协同处置含铜污泥应用提供参考。Abstract: An experimental study to handle Copper-containing sludge by cement kiln technology was presented in the paper. Cement clinker was produced with raw meal after adding various amount of Copper-containing sludge. The effects of copper-containing sludge on the properties of silicate cement clinker and the leaching of heavy metals within the sludge on the environmental safety were discussed. Results indicated that an appreciate amount of Copper-containing sludge as mixed into raw meals would improve its burnability. An proper proportion sludge would not cause clinker’s mineral compositions change, while significantly reducing its f-CaO contents. Depending on the amount of sludge as mixed into the raw meals, Copper-containing sludge had a significant effect on hydration and mechanical strength of the silicate cement. It was found that the Copper-containing sludge would effectively promote the hydration of silicate cement when amount of sludge in raw meal was 4%, resulting in an increase of its compressive strengths, however, cement hydration would deteriorate if amount of sludge exceeded 4.0%, as a result, mechanical strength of silicate cement decreased. Curing of clinker minerals was prone to heavy metal elements, both SEM-EDS images and the split-phase extraction method confirmed that Cu elements were mainly cured as intermediate phase in the cement clinker - this curing rate could reach as high as 87%. The amount of copper ions leached in cement slurry was usually small, lower than the limit as allowed in Standard for industrial solid waste, indicating that Copper ion cured in clink is stable, and would not cause secondary pollution to the environment. This study can provide a reference for cement kiln co-disposal of Copper-containing sludge.
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Key words:
- copper-containing sludge /
- cement kiln co-disposal /
- solidification /
- compressive strength /
- leaching
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表 1 生料化学组成
Table 1. Chemical compositions a of cement raw material (calculated by mass fraction)
% CaO SiO2 Fe2O3 Al2O3 MgO K2O P2O5 Na2O 42.75 13.96 2.35 3.33 0.97 0.932 2.46 1.42 表 2 含铜污泥化学组成
Table 2. Contents of chemical components in copper-containing sludge (calculated by mass fraction)
% CuO SO3 SiO2 Al2O3 CaO Fe2O3 K2O TiO2 其他杂质 39.69 25.45 12.57 10.8 1.82 0.796 0.057 0.054 8.76 表 3 掺含铜污泥熟料的中间相和硅酸盐相的质量分数
Table 3. Content of intermediate and silicate phases of clinker mixed with copper-containing sludge
样品编号 含铜污泥掺量/% Cu的质量/g Cu的质量分数/% 熟料 中间相 硅酸盐相 中间相 硅酸盐相 R-I 0 2.016 0.424 — 21.05 — R-S 0 3.022 — 2.344 77.56 C1-I 2.0 2.014 0.427 — 21.24 — C2-I 4.0 2.025 0.432 — 21.52 — C3-I 6.0 2.032 0.439 — 22.11 — C4-I 8.0 2.018 0.433 — 22.46 — C5-I 10.0 2.023 0.430 — 22.55 — C1-S 2.0 3.015 — 2.330 — 77.28 C2-S 4.0 3.014 — 2.332 — 77.37 C3-S 6.0 3.020 — 2.336 — 77.20 C4-S 8.0 3.011 — 2.338 — 77.65 C5-S 10.0 3.022 — 2.338 — 77.37 注:样品编号中,R为空白组、C为掺加含铜污泥的样品组、I为中间相、S为硅酸盐相。 表 4 中间相和硅酸盐相中Cu离子的质量分数
Table 4. Content of heavy metal in different phases of clinker
样品编号 含铜污泥掺量/% Cu离子固化质量分数/ (mg·kg-1) 中间相 硅酸盐相 C1 2.0 18 124.22 1 582.72 C2 4.0 39 655.38 3 246.35 C3 6.0 62 571.89 4 986.77 C4 8.0 78 542.90 6 650.88 C5 10.0 99 852.05 8 462.26 表 5 Cu离子在熟料中的固化率
Table 5. Solidification rate of Cu ion in cement clinker
样品编号 含铜污泥掺量/% Cu离子质量分数/(mg·kg−1) 固化率/% 原料中 熟料中 C1 2% 3 456.68 4 184.97 77 C2 4% 5 015.62 6 860.99 87 C3 6% 8 420.77 9 135.75 69 C4 8% 12 062.60 12 517.79 66 C5 10% 13 430.99 13 726.64 65 -
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