Ekubatsion Lulit H, Thriveni Thenepalli, Ahn Ji W
Resources Recycling Department, University of Science and Technology (UST), 217, Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea.
School of Civil and Environmental Engineering Department, Addis Ababa Institute of Technology (AAiT), Addis Ababa University, Addis Ababa 1000, Ethiopia.
ACS Omega. 2021 Oct 13;6(42):27600-27609. doi: 10.1021/acsomega.1c00946. eCollection 2021 Oct 26.
The effect of heavy metals in aqueous solutions has been addressed by several methods. Precipitation using lime, slaked or quick, is one of the commonly used techniques. In this work, KR-slag was used in addition to Ca(OH) that served as a seeding material. Furthermore, CO has been injected into the suspensions for pH stabilization, which further increases the removal efficiency. Accordingly, results have shown a great performance regarding both removal efficiency and reduced sludge production. More than 99% of Cd and Pb was removed with 1 g/L of KR-slag, 0.5 g/L of Ca(OH), and CO injection at a rate of 1 L/min. The effect of carbonation has been evaluated by examining the removal efficiency before and after carbonation. Following the injection of CO, removal efficiency has increased from 58.7 to 99.8 and 71.2 to 99.3% for Cd and Pb, respectively. Moreover, sludge volume from this treatment method was obtained as 103 mL/L, which is much less than the sludge volume obtained from the carbonation of only Ca(OH), that is, 361 mL/L. Leaching of residues was also conducted to evaluate the environmental performance of the removal process. After carbonation, there was a lower concentration of metals when leached out in a wide range of pH solutions. Contrarily, it was observed that a relatively higher concentration of metals was released in acidic solutions due to the substitution of metal ions (Cd and Pb) with H ions. Residues were then characterized by X-ray diffraction and differential thermal analysis/thermogravimetric analysis for phase identification. Both characterizations detected the presence of CaCO, which was an indication of the transformation of Ca(OH) to CaCO.
水溶液中重金属的影响已通过多种方法进行了研究。使用熟石灰或生石灰进行沉淀是常用技术之一。在这项工作中，除了用作晶种材料的Ca(OH)₂外，还使用了KR矿渣。此外，已将CO注入悬浮液中以稳定pH值，这进一步提高了去除效率。因此，结果表明在去除效率和减少污泥产量方面都有出色表现。使用1 g/L的KR矿渣、0.5 g/L的Ca(OH)₂并以1 L/min的速率注入CO时，Cd和Pb的去除率超过99%。通过检查碳化前后的去除效率来评估碳化的影响。注入CO后，Cd和Pb的去除效率分别从58.7%提高到99.8%和从71.2%提高到99.3%。此外，这种处理方法产生的污泥体积为103 mL/L，远低于仅对Ca(OH)₂进行碳化时产生的污泥体积，即361 mL/L。还对残渣进行了浸出试验以评估去除过程的环境性能。碳化后，在广泛的pH值溶液中浸出时金属浓度较低。相反，观察到在酸性溶液中由于H⁺离子取代金属离子（Cd和Pb）而释放出相对较高浓度的金属。然后通过X射线衍射和差示热分析/热重分析对残渣进行表征以鉴定相。两种表征都检测到了CaCO₃的存在，这表明Ca(OH)₂转化为了CaCO₃。
