Wang Xingdong, Wei-Chung Chang Victor, Li Zhiwei, Song Yang, Li Chunxing, Wang Yin
CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Department of Civil Engineering, 23 College Walk, Monash University, Victoria 3800, Australia.
Department of Civil Engineering, 23 College Walk, Monash University, Victoria 3800, Australia.
Waste Manag. 2022 Mar 15;141:231-239. doi: 10.1016/j.wasman.2022.02.001. Epub 2022 Feb 9.
Food waste digestate (FWD) is a desirable additive in sewage sludge (SS)-based biochar preparation owing to its high contents of intrinsic inorganic minerals and lignocellulosic compounds. In this study, we investigated the co-pyrolysis of SS with FWD at different mixing ratios (4:0, 3:1, 2:2, 1:3, and 0:4; SS:FWD w/w) at 550 °C to synergistically improve the biochar characteristics and immobilize the heavy metals in the SS. The results showed that co-pyrolysis of SS with FWD greatly increased the aromaticity and pH (by 13.22-26.56%) of the blended biochar, and significantly reduced the contents of total and bioavailable heavy metals. The addition of FWD effectively enhanced the conversion of heavy metals from less stable fractions to more stable forms, but led to the transformation of Cr from the residual fraction (F4) to the oxidizable fraction (F3) when the FWD:SS ratio was ≥ 3:1. Overall, the formation of co-crystal compounds, stable kaolinite, and metal oxides together with the enhancement of biochar characteristics during co-pyrolysis significantly reduced the heavy metal-associated ecological risk (potential ecological risk index lower than 15.51) and phytotoxicity (germination index higher than 139.41%) of the blended biochar. These findings suggest that high levels of mineral components in FWD greatly immobilize more heavy metals in biochar.
由于食物垃圾消化物（FWD）含有高含量的固有无机矿物质和木质纤维素化合物，因此它是基于污水污泥（SS）制备生物炭时理想的添加剂。在本研究中，我们研究了在550℃下，SS与FWD以不同混合比例（4:0、3:1、2:2、1:3和0:4；SS:FWD质量比）进行共热解，以协同改善生物炭特性并固定SS中的重金属。结果表明，SS与FWD共热解极大地提高了混合生物炭的芳香性和pH值（提高了13.22 - 26.56%），并显著降低了总重金属和生物可利用重金属的含量。添加FWD有效地促进了重金属从较不稳定组分向更稳定形态的转化，但当FWD:SS比例≥3:1时，会导致Cr从残留组分（F4）转化为可氧化组分（F3）。总体而言，共热解过程中共晶化合物、稳定高岭土和金属氧化物的形成以及生物炭特性的增强显著降低了混合生物炭的重金属相关生态风险（潜在生态风险指数低于15.51）和植物毒性（发芽指数高于139.41%）。这些发现表明，FWD中的高含量矿物成分能极大地固定生物炭中的更多重金属。
