Abstract A stepwise microwave synergistic pyrolysis (SMSP) approach is proposed as a new way to relieve disposal problems of the sewage sludge. Here the sludge is first pre-pyrolyzed by a conventional heating stage, and then rapidly pyrolyzed by a microwave-induced heating stage without any extra microwave absorbers or blending needed. Under simulated process pyrolysis conditions, the dried sludge, intermediate and final sludge-based biochar samples were prepared in the laboratory. Their chemical composition, microstructure and morphology, and leaching toxicity of heavy metals were carefully characterized and analyzed by various techniques such as proximate and ultimate analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and scanning electron microscope equipped with energy-dispersive x-ray spectroscopy (SEM-EDX). Results showed that the pre-pyrolytic biochar can be rapidly heated up to 1100 °C within 5 min under microwave irradiation. The pre-pyrolytic stage increased the carbonization and ash enrichment degree of the sludge which itself acted as a good microwave absorber while achieving a quick temperature rise under microwave irradiation. The ash remaining ratio and the specific surface area of the biochar derived from the SMSP approach (labelled as SBC2) are increased by 6.46% and 16.17% respectively, compared with the conventional biochar sample (SBC1). And SBC2 still had diverse surface functional groups kept after SMSP. The residual ratios of Ni, Cu, Zn, Pb, Cr and Cd in SBC2 was more noticeable than in SBC1 but the leaching ratios quite the contrary. Vitrification is also well proved by the increment of quartz peak detected by XRD tests, and the formation of melted glassy spheres with elemental composition of Si, Ca, Al observed by SEM-EDX. It can favorably increase solidification level and decrease leaching toxicity of heavy metals in the SBC2. The feasibility of this proposed SMSP concept has been positively supported by our experimental results. The properties of the sludge-based biochar produced from the SMSP approach also show great potential to be utilized as precursors to produce various adsorbents.

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一种生产污泥基生物炭的逐步微波协同热解方法：实验室模拟的可行性研究

摘要 逐步微波协同热解（SMSP）方法是解决污水污泥处理问题的一种新方法。在这里，污泥首先通过常规加热阶段预热解，然后通过微波诱导加热阶段快速热解，无需任何额外的微波吸收剂或混合。在模拟过程热解条件下，干燥污泥、中间体和最终污泥基生物炭样品在实验室制备。它们的化学成分、微观结构和形貌以及重金属的浸出毒性通过各种技术进行了仔细的表征和分析，例如近似分析和最终分析、X 射线衍射 (XRD)、傅里叶变换红外 (FTIR) 光谱、Brunauer-Emmett-Teller （赌注），和配备能量色散 X 射线光谱仪 (SEM-EDX) 的扫描电子显微镜。结果表明，预热解生物炭在微波照射下可以在 5 分钟内迅速加热至 1100 ℃。预热解阶段提高了污泥的碳化和富灰度，污泥本身起到了良好的微波吸收剂的作用，同时在微波照射下实现了快速升温。与常规生物炭样品（SBC1）相比，SMSP 方法（标记为 SBC2）得到的生物炭的灰分剩余率和比表面积分别增加了 6.46% 和 16.17%。SBC2在SMSP之后仍然保留着不同的表面官能团。SBC2 中 Ni、Cu、Zn、Pb、Cr 和 Cd 的残留比例比 SBC1 中更显着，但浸出率恰恰相反。通过 XRD 测试检测到的石英峰的增加以及通过 SEM-EDX 观察到的元素组成为 Si、Ca、Al 的熔融玻璃球的形成也很好地证明了玻璃化。它可以有利地提高 SBC2 中重金属的凝固水平并降低重金属的浸出毒性。我们的实验结果积极支持了这一提议的 SMSP 概念的可行性。通过 SMSP 方法生产的污泥基生物炭的特性也显示出巨大的潜力，可用作生产各种吸附剂的前体。它可以有利地提高 SBC2 中重金属的凝固水平并降低重金属的浸出毒性。我们的实验结果积极支持了这一提议的 SMSP 概念的可行性。通过 SMSP 方法生产的污泥基生物炭的特性也显示出巨大的潜力，可用作生产各种吸附剂的前体。它可以有利地提高 SBC2 中重金属的凝固水平并降低重金属的浸出毒性。我们的实验结果积极支持了这一提议的 SMSP 概念的可行性。通过 SMSP 方法生产的污泥基生物炭的特性也显示出巨大的潜力，可用作生产各种吸附剂的前体。