School of Resources and Environmental Engineering, Shanghai Polytechnic University, Shanghai, 201209, China; College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
School of Resources and Environmental Engineering, Shanghai Polytechnic University, Shanghai, 201209, China.
J Environ Manage. 2022 Mar 1;305:114292. doi: 10.1016/j.jenvman.2021.114292. Epub 2022 Jan 5.
The presence of unstable heavy metals in sewage sludge (SS) restricts its resource utilization. In this study, Ca(HPO) and SS were co-pyrolyzed to produce biochar, which contained relatively stable heavy metals. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and inductively coupled plasma atomic emission techniques were used to analyze the physical and chemical properties and heavy metal content of the biochar. The results indicated that co-pyrolysis of SS with Ca(HPO) resulted in the production of more stable heavy metals in the SS. The optimal co-pyrolysis conditions were a blended ratio of 15% Ca(HPO), 650 °C final temperature, 15 °C min, and 60 min retention time. The potential stabilization mechanisms of heavy metals were as follows: (1) organic decomposition and moisture (sourced from Ca(HPO) decomposition) evaporation resulted in greater biochar surface porosity; (2) phosphorous substances were complexed with heavy metals to form metal phosphates; and (3) the mixture reactions among inorganic substances, pyrolysis products of organics, and heavy metals resulted in the formation of highly aromatic metallic compounds. Additionally, the potential environmental risks posed by the heavy metals decreased from 65.73 (in SS) to 4.39 (in biochar derived from co-pyrolysis of SS and 15% of Ca(HPO)). This study reports on a good approach for the disposal of SS and the reduction of its environmental risk.
污水污泥 (SS) 中不稳定重金属的存在限制了其资源利用。在本研究中，采用 Ca(HPO) 和 SS 共热解制备生物炭，使其中相对稳定的重金属得以保留。采用 X 射线衍射光谱、傅里叶变换红外光谱和电感耦合等离子体原子发射技术分析了生物炭的物理化学性质和重金属含量。结果表明，SS 与 Ca(HPO) 的共热解导致 SS 中重金属的稳定性增加。共热解的最佳条件为 Ca(HPO) 比例为 15%，最终温度为 650°C，升温速率为 15°C min，保留时间为 60 min。重金属的潜在稳定机制如下：（1）有机分解和水分（来自 Ca(HPO) 分解）蒸发导致生物炭表面孔隙率增加；（2）磷物质与重金属形成金属磷酸盐；（3）无机物、有机物热解产物和重金属之间的混合反应形成高芳烃金属化合物。此外，重金属的潜在环境风险从 SS 中的 65.73 降低到了 SS 和 15% Ca(HPO) 共热解生物炭中的 4.39。本研究报道了一种处理 SS 和降低其环境风险的有效方法。
