Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong.
Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
Sci Total Environ. 2023 Jun 15;877:162871. doi: 10.1016/j.scitotenv.2023.162871. Epub 2023 Mar 16.
The disposal of wastewater sludge is one of the most challenging environmental problems for large cities. Wastewater sludge may be utilized as a feasible substitute for clay to sinter ceramics, given their similar mineralogical composition. However, the organics in sludge will be wasted, while their release during sintering will leave cracks in the ceramic products. In this research, after the thermal treatment for effective organic recovery, the thermally hydrolyzed sludge (THS) is incorporated with clay for the sintering of construction ceramics. The experimental results showed that a THS dosing ratio up to 40 % can be achieved for mixing with montmorillonite clay to make ceramic tiles. The sintered tiles (THS-40) had an intact shape and structure, and the tile performance was close to that made from single montmorillonite (THS-0), with water absorption of 0.4 % vs. 0.2 %, compressive strength of 136.8 vs. 140.7 MPa, and undetected heavy metal leaching. Further addition of THS would lead to a considerable deterioration of the quality of the tiles to a compressive strength of as low as 5.0 MPa for the THS only product (THS-100). Comparing with the tiles incorporated with raw sludge (RS-40), the THS-40 tiles had a more intact and denser structure with a 10 % improved compressive strength. Cristobalite, aluminum phosphate, mullite, and hematite dominated in the THS-born ceramics, which are typical components of ceramics, and the amount of hematite increased with the THS dosing ratio. Sintering at a high temperature of 1200 °C enabled efficient phase transformation from quartz to cristobalite and from muscovite to mullite, which ensured the toughness and compactness of the THS-born ceramic tiles.
城市污泥的处理是大型城市面临的最具挑战性的环境问题之一。鉴于污泥和粘土具有相似的矿物成分，将污泥用作烧结陶瓷的可行替代粘土是可行的。然而，污泥中的有机物将被浪费掉，而它们在烧结过程中的释放会在陶瓷制品中留下裂缝。在这项研究中，在进行有效的有机物回收的热处理后，将热解污泥（THS）与粘土混合用于建筑陶瓷的烧结。实验结果表明，THS 与蒙脱石粘土混合的剂量比高达 40%可用于制造瓷砖。烧结的瓷砖（THS-40）具有完整的形状和结构，瓷砖性能与仅使用蒙脱石的瓷砖（THS-0）接近，吸水率为 0.4%对 0.2%，抗压强度为 136.8 对 140.7 MPa，未检测到重金属浸出。进一步添加 THS 会导致瓷砖质量严重恶化，仅 THS 产品（THS-100）的抗压强度低至 5.0 MPa。与掺入原始污泥（RS-40）的瓷砖相比，THS-40 瓷砖具有更完整和致密的结构，抗压强度提高了 10%。THS 衍生陶瓷中主要存在方石英、磷酸铝、莫来石和赤铁矿，这些都是陶瓷的典型成分，并且赤铁矿的量随着 THS 剂量比的增加而增加。在 1200°C 的高温下烧结可实现石英向方石英和云母向莫来石的高效相变，从而确保了 THS 衍生陶瓷砖的韧性和致密性。
