摘要
大量的脱墨污泥是目前废纸制浆企业面临的重要环境问题之一。脱墨污泥的合理资源化利用是解决当前困境的有效途径。本文分析了脱墨污泥的基本性质,包括不同废纸制浆脱墨污泥的主要成分、金属离子含量和有机污染物等;基于近几年国内外的相关研究成果,综述了脱墨污泥资源化利用在生物炭、生物油、回收有机物和无机物、堆肥与厌氧消化、营养基和生物复合材料等方面的最新研究进展和应用前景。
近年来,我国废纸回收率逐年上升;2019年,我国废纸回收率为49
脱墨污泥由纤维、填料、涂料、油墨和脱墨剂等组
注 —未报道;* 900℃测定值,其他均为550℃测定值。
脱墨污泥中的有机物以纤维为主,其占比约为44.1 wt%~96.9 wt
脱墨污泥中的无机物主要来自填料,如碳酸钙(CaCO3)、高岭土(Al2O3·2SiO2·2H2O)、滑石粉(Mg3Si4O10(OH)2)和钛白粉(TiO2
注 —未报道;*基于灰分计算,其他基于绝干污泥质量计算。
绝干脱墨污泥中占比最高的6种金属元素分别为Ca、Al、Mg、Na、Fe和Ti,其含量分别为11.5 wt%~27.0 wt%、1.47 wt%~3.57 wt%、0.29 wt%~0.93 wt%、0.12 wt%~0.28 wt%、0.13 wt%~0.21wt% 和0~0.13 wt
Beauchamp
脱墨污泥中纤维和油墨等有机物含量高,具有制备碳基吸附材料的潜力。采用脱墨污泥制备的生物炭或碳基吸附材料,能有效去除废水中的有机污染物和吸附固着在土壤中的重金属。闫中亚
Paz-Ferreiro
生物油(热解油)作为一种可再生能源,具有很大的应用潜力。生物油是生物质在热解过程中产生的、由水与各种复杂的含氧有机化合物及大量的低聚物组成的物质。脱墨污泥可作为原料,通过热解反应直接生产高附加值的生物油。Ouadi
然而,传统木质原料热解产生的生物油普遍存在含氧量(35 wt%~40 wt%)、含水量较高(15 wt%~30 wt%)和耐热性能较差等问题,导致其热值较传统燃料油低、黏度高且稳定性较差,无法直接被发动机或涡轮使用;因此,需要进一步提质(如催化加氢脱氧)和精炼改
通过热解脱墨污泥可以得到高附加值的有机物(气相产物和生物油)和无机固体残渣。气相产物在合成气领域、生物油在燃料与精细化学品领域都具有巨大应用潜力,固体残渣可以作为造纸工业用填料进行回收利用。因此,对废纸制浆厂而言,这种回收脱墨污泥中有机物和无机物的方式,既能减轻经济负担,又能增加环境效益。
Lou
脱墨污泥具有高碳低氮的性质(见
厌氧消化不仅可以降低脱墨污泥中有机物的含量,还可以获得甲烷气,回收能量。Amare
脱墨污泥的高纤维含量不仅提高了其作为营养基的有机质含量,而且使其非常适合用于改善苗圃生长基质的物理性质(如孔隙率、持水能力和通气性)。Vannucchi
脱墨污泥中的纤维素成分可以作为直接碳源或间接碳源用于培养工业所需的微生物,可以用低成本培养出具有高活性的工业酶,且酶对纤维素的降解作用还可以大幅降低脱墨污泥的体积,有利于降低后续填埋等处理成本。由于脱墨污泥成分复杂,可能含有对微生物生长繁殖不利的毒性物质,需要对脱墨污泥进行必要的预处理。Weiss
脱墨污泥中的纤维和灰分含量高,其中,灰分可以作为塑料制品的填料,采用脱墨污泥作为填料或增强剂与高密度聚乙烯复合制备生物复合材料,可以改善塑料的机械性能,如拉伸强度和杨氏模量等。
Elloumi
除上述应用外,脱墨污泥在替代再生纤维、制砖、水泥加填剂和燃料乙醇等方面也有着广泛的应用前景。
Yin
Singh
脱墨污泥中有机物和残留的纤维一般被认为可以改变水泥砂浆的物理与机械特性(如流动性能、凝结时间和吸水率)。Yan
脱墨污泥中含有大量的细小纤维,也是一种很有吸引力的生物质资源,其成本低且无需严格的预处理即可进行酶解发酵并制备燃料乙醇。Chen
在脱墨污泥产量大及污泥处理处置国家政策新导向的背景下,脱墨污泥资源化利用是解决再生纤维制浆企业环境问题的关键。脱墨污泥中纤维含量和灰分都较高,是一种有较高利用价值的潜在资源。近年来,国内外对脱墨污泥资源化进行了大量的研究,特别在脱墨污泥热解(制备生物炭和生物油等)、堆肥和营养基等方面已取得一定成果。目前,国内对脱墨污泥的资源化利用项目集中在利用脱墨污泥进行再造纸(2019年岳阳林纸股份有限公司的脱墨污泥综合利用项目,2018年浙江山鹰纸业有限公司的造纸脱墨污泥回用生产瓦楞原纸技改项目)。由于受造纸原料波动和生产工艺影响,脱墨污泥成分复杂且变化大,造成其在资源化利用过程中产品质量或工艺条件控制困难,限制了脱墨污泥的资源化利用转向产业化应用。因此,今后脱墨污泥的产业化应用,需要从脱墨污泥生命周期的角度对产品价值与应用成本进行综合考虑。
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