Hubei Key Laboratory of Ecological Restoration of River-Lakes and Algal Utilization, Hubei University of Technology, Wuhan, China.
Acid and Metalliferous Mine Drainage, Blue Minerals Consultancy, Wattle Grove, Tasmania, Australia.
Water Environ Res. 2021 Dec;93(12):3064-3074. doi: 10.1002/wer.1658. Epub 2021 Dec 4.
Heavy metals and metalloids, in sludge and sediments, are environmental pollutants of concern with long-term negative effects on human and ecological health. In this study, sludge from biological treatment of municipal waste leachate was pyrolyzed into leachate sludge-derived biochar (LSDB) at 300°C to 900°C, comprising complex organic and inorganic (particularly heavy metals) species formed from heterogeneous chemical reactions. Based on different advanced material analyses, that is, Thermogravimetric Analysis (TGA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis, this study revealed that mass loss and microstructural changes of LSDBs occurred primarily due to decomposition of volatiles, aromatic rings, carbonates, and hydroxides. The leaching behaviors of heavy metals from LSDBs were evaluated using the Synthetic Precipitation Leaching Procedure (SPLP). The final pH in SPLP increased from 7.5 to 12.5 with pyrolysis temperature. The pH increase favored the retention of heavy metals in the LSDBs due to the formation of low soluble precipitates at alkaline pH. The heavy metals and metalloids in the LSDBs were present as surface precipitates due to precipitation and cation exchange rather than surface complexation. The leaching contents of metals and metalloids, such as Cr, Cd, Ni, Pb, and As, were all below their respective maximum discharge standards for the first priority pollutants in China.
重金属和类金属是环境污染物，它们在污泥和沉积物中存在，对人类和生态健康有长期的负面影响。在这项研究中，城市垃圾渗滤液生物处理产生的污泥在 300°C 到 900°C 的温度下进行热解，生成了渗滤液污泥衍生生物炭（LSDB），其中包含了由异质化学反应形成的复杂有机和无机（特别是重金属）物质。基于不同的先进材料分析，即热重分析（TGA）、傅里叶变换红外（FTIR）、扫描电子显微镜（SEM）和 X 射线衍射（XRD）分析，本研究表明 LSDB 的质量损失和微观结构变化主要是由于挥发物、芳环、碳酸盐和氢氧化物的分解。采用合成沉淀浸出程序（SPLP）评估了 LSDB 中重金属的浸出行为。随着热解温度的升高，SPLP 中的最终 pH 值从 7.5 增加到 12.5。由于在碱性 pH 值下形成了低溶解度的沉淀，pH 值的增加有利于重金属在 LSDB 中的保留。LSDB 中的重金属和类金属以表面沉淀物的形式存在，这是由于沉淀和阳离子交换而不是表面络合。Cr、Cd、Ni、Pb 和 As 等金属和类金属的浸出含量均低于中国第一类优先污染物的最大排放标准。
