School of Land Resources and Environment, Key Laboratory of Agricultural Resource and Ecology in the Poyang Lake Basin of Jiangxi Province, Jiangxi Agricultural University, Nanchang 330045, PR China.
School of Land Resources and Environment, Key Laboratory of Agricultural Resource and Ecology in the Poyang Lake Basin of Jiangxi Province, Jiangxi Agricultural University, Nanchang 330045, PR China.
Sci Total Environ. 2022 Jan 10;803:149874. doi: 10.1016/j.scitotenv.2021.149874. Epub 2021 Sep 1.
The treatment of sewage sludge (SS) is an environmental problem worldwide. In recent years, hydrothermal carbonization (HTC) of SS for hydrochar (HC) has attracted extensive attention. This study preliminarily explored the microwave-assisted HTC of SS for the first time. Increasing the reaction temperature (150-250 °C) and reaction time (0-120 min) resulted in a decrease in the HC yield, and it gradually increased with the rising solid-liquid ratio (0.03-0.25 g/mL). Compared with raw SS, the HC products possessed higher aromaticity, carbonization degree, porosity, and polarity, and lower content of soluble nutrients (N/P/K) and leachable heavy metals (Cu, Zn, Pb, Cd, Cr, and Ni), indicating a lower risk of nutrient and heavy metal loss. Attention should be paid to the total contents of Zn and Cd in HC exceeded the permitted value for use in cultivated land with edible crops. The use of CaO as a catalyst improved the yield of HC, made the HC and process water (PW) weakly alkaline, and further passivated the heavy metals in the HC. In the case of HPO, although the conversion of SS was enhanced (lower content of volatile organic matter in HC), the contents of soluble nutrients (N/P/K) in HC/PW increased, and the migration of Zn and Cd into process water was enhanced. The HCs obtained in this study had poor combustion properties, but higher ignition temperatures than raw SS. PW must be properly treated or recycled because it still contained high contents of organic matter and nutrients. This fundamental study provides basic insights into the microwave-assisted HTC of SS.
污水污泥（SS）的处理是一个全球性的环境问题。近年来，SS 的水热碳化（HTC）制备水热炭（HC）受到广泛关注。本研究首次初步探索了 SS 的微波辅助 HTC。升高反应温度（150-250°C）和反应时间（0-120 分钟）导致 HC 产率降低，而随着固液比（0.03-0.25 g/mL）的升高逐渐增加。与原始 SS 相比，HC 产物具有更高的芳香度、碳化度、孔隙率和极性，以及更低的可溶性养分（N/P/K）和可浸出重金属（Cu、Zn、Pb、Cd、Cr 和 Ni）含量，表明养分和重金属损失的风险较低。应注意 HC 中 Zn 和 Cd 的总量超过了可用于种植食用作物耕地的允许值。使用 CaO 作为催化剂提高了 HC 的产率，使 HC 和工艺水（PW）呈弱碱性，并进一步使 HC 中的重金属钝化。在 HPO 的情况下，尽管 SS 的转化率提高（HC 中挥发性有机物含量较低），但 HC 中的可溶性养分（N/P/K）含量增加，Zn 和 Cd 向工艺水的迁移增强。本研究中获得的 HC 具有较差的燃烧性能，但比原始 SS 具有更高的着火温度。PW 必须进行适当的处理或回收，因为它仍然含有高含量的有机物和养分。这项基础研究为 SS 的微波辅助 HTC 提供了基本的见解。
