Chen Min, Zhang Qiwu, Jiang Lin, Hu Huimin, Wang Chao, Li Zhao
School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China.
School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China.
J Hazard Mater. 2022 Feb 15;424(Pt A):127272. doi: 10.1016/j.jhazmat.2021.127272. Epub 2021 Sep 20.
Utilization of natural clay minerals for the treatment of heavy metal cadmium contamination is appealing as the affordable and readily accessible raw materials. However, the low reactivity of natural serpentine limits its practical application for Cd removal. In the present study, mechanochemical activation of antigorite-type serpentine (SP) as example was introduced to enhance its removal capacity for heavy metal of cadmium high enough for practical use. It was found ball-milling at 600 rpm for 60 min for antigorite resulted in the increased release of hydroxyl group to facilitate the precipitation of Cd, giving a capacity of 27.4 mg/g for the treatment of 100 mg/L Cd for 120 min at room temperature, which was 10 times higher than that of the pristine antigorite (2.5 mg/g). More significantly, magnesium sulfate (MgSO, MS) was introduced for the first time to process antigorite, thus to form MgSO-incorporated antigorite. As a result, the removal capacity for Cd was dramatically increased to 239.7 mg/g with the equal antigorite dosage (the molar ratio of SP/MS = 1:0.5), which is also much higher than the other reported clay minerals. Results showed that, MgSO incorporation promoted the reactivity of antigorite and provided numerous SO active sites, which allowed the heterogeneous nucleation of basic cadmium sulfate (CdSO·3.5 Cd(OH)·xHO) precipitate on antigorite, therefore not requiring high alkalinity support as the conventional formation of cadmium hydroxide does. Correspondingly, under the new mechanism, the Cd precipitation could take place in a wide pH range, even from pH 3.0, which was a rarely reported phenomenon happening on natural minerals. Based on these findings, this study demonstrated the effectiveness of mechanochemical incorporation of sulfate for enhancing the Cd removal capacity of serpentine, as well as the high efficiency of new pathway for Cd precipitation. Moreover, the potential of low-cost serpentine as alternative stabilizers for the highly-effective remediation of heavy metal contamination may be expected.
利用天然粘土矿物处理重金属镉污染具有吸引力，因为其原料价格低廉且易于获取。然而，天然蛇纹石的低反应活性限制了其在去除镉方面的实际应用。在本研究中，以叶蛇纹石型蛇纹石（SP）为例，引入机械化学活化方法以提高其对重金属镉的去除能力，使其高到足以实际应用。研究发现，叶蛇纹石在600转/分钟下球磨60分钟会导致羟基释放增加，从而促进镉的沉淀，在室温下处理100毫克/升的镉120分钟时，其去除能力为27.4毫克/克，这比原始叶蛇纹石（2.5毫克/克）高出10倍。更重要的是，首次引入硫酸镁（MgSO₄，MS）对叶蛇纹石进行处理，从而形成含硫酸镁的叶蛇纹石。结果，在叶蛇纹石用量相同的情况下（SP/MS的摩尔比 = 1:0.5），镉的去除能力大幅提高到239.7毫克/克，这也远高于其他报道的粘土矿物。结果表明，硫酸镁的掺入促进了叶蛇纹石的反应活性并提供了大量的SO₄²⁻活性位点，这使得碱式硫酸镉（CdSO₄·3.5Cd(OH)₂·xH₂O）沉淀在叶蛇纹石上发生非均相成核，因此不像传统氢氧化镉形成那样需要高碱度支持。相应地，在新机制下，镉沉淀可以在很宽的pH范围内发生，甚至从pH 3.0开始，这是在天然矿物上很少报道的现象。基于这些发现，本研究证明了通过机械化学掺入硫酸盐来提高蛇纹石去除镉能力的有效性，以及镉沉淀新途径的高效性。此外，可以预期低成本蛇纹石作为高效修复重金属污染替代稳定剂的潜力。
