石灰石耦合AMD内源铁氧化物去除重金属的机制

Study on the Removal Mechanism of Heavy Metals in AMD by Calcite with Interior Iron Oxides

该文通过添加石灰石中和分别来源铜矿和煤矿的3种酸性矿山废水(AMD),研究石灰石耦合AMD-Ⅰ(铜矿)、AMD-Ⅱ(煤矿)和AMD-Ⅲ(煤矿)中内源Fe对Cu、As、Zn的去除效果。选取富含Fe^(2+)和Fe^(2+)的同一地区废水(AMD-Ⅱ和AMD-Ⅲ),设计温度、时间和温度+时间因素,阐明时间条件对不同Fe^(2+)/Fe^(2+)AMD沉积物中铁氧化物形貌与晶型的变化,同时用高温加速反应进程,推演石灰石耦合内源铁氧化物对Cu、As、Zn去除的稳定化机制。结果表明,室温条件下,石灰石处理后3种AMD中Cu和As随着Fe的沉降同步去除,在2 h时去除率已经达到94.53%~99.99%,而Zn的去除均相对滞后,2 h的去除率仅为5.06%、54.09%和26.71%,说明Zn的去除方式受来源、水质特性影响较大。随着时间的增加(90 d),AMD-Ⅲ(Fe^(2+)含量85.24%)产生的沉积物中铁氧化物由最初的水铁矿向纤铁矿转变,AMD-Ⅰ中铁氧化物向纤铁矿和针铁矿转变,而AMD-Ⅱ(Fe^(2+)含量47.75%)中在整个培养期内仍为最初的水铁矿。因此,AMD的初始pH、内源Fe^(2+)/Fe^(2+)的比例是决定石灰石处理后沉积物中铁氧化物的组成与形貌的主要因素。随着温度、时间或温度+时间的增加,在AMD-Ⅲ(Fe^(2+)含量85.24%)的最终沉积物中铁氧化物主要表现为针铁矿和磁铁矿,AMD-Ⅱ(Fe^(2+)含量21.62%)主要为赤铁矿。而且,整体变化过程中供试的AMD-Ⅱ和AMD-Ⅲ中Cu、As、Zn均没有重新释放至液相,且其变化规律与室温一致。研究结果对正确处理和处置石灰石中和AMD后产生的沉积物有一定的指导意义。

By adding limestone to neutralize three kinds of acid mine drainage(AMD) from copper mine and coal mine,the removal efficiency of Cu, As and Zn by limestone coupled with endogenous Fe in AMD-Ⅰ(copper mine), AMD-Ⅱ(coal mine) and AMD-Ⅲ(coal mine) was studied. The wastewater from the same area(AMD-Ⅱ and AMD-Ⅲ) rich in Fe^(2+)and Fe^(2+)was selected. The factors of temperature, time and temperature + time were designed to clarify the effect of time on the morphology and crystal form of iron oxides in different Fe^(2+)/Fe^(2+)AMD sediments. Meanwhile, the reaction process was accelerated by high temperature, and the stabilization mechanism of Cu, As and Zn removal by limestone coupled with endogenous iron oxides was deduced. The results showed that at room temperature, Cu and As in the three kinds of AMD were removed simultaneously with the deposition of Fe, and the removal rate reached 94.53%~99.99% at 2 h, while Zn removal was relatively lagging behind, and the removal rate was only 5.06%, 54.09% and 26.71% at 2 h. With the increase of time(90 days), the iron oxides in the sediments produced by AMD-Ⅲ(Fe^(2+)content 85.24%) changed from the initial ferrihydrite to the lepidocrocite, AMD-Ⅰ changed to the lepidocrocite and goethite, while AMD-Ⅱ(Fe^(2+)content 47.75%) was still the initial ferrihydrite in the whole culture period. Therefore, the initial pH of AMD and the ratio of endogenous Fe^(2+)/Fe^(2+)are the main factors that determine the composition and morphology of iron oxides in limestone treated sediments. With the increase of temperature, time or temperature + time, the iron oxides in AMD-Ⅲ(Fe^(2+)content 85.24%) final sediments are mainly goethite and magnetite, and AMD-Ⅱ(Fe^(2+)content 21.62%) is mainly hematite. In addition, Cu, As and Zn in AMD-Ⅱand AMD-Ⅲ did not re-release to the liquid phase during the whole change process, and the change rule was consistent with that at room temperature. The research results have certain guiding significance for the correct treatment and disposal of the sediment produced by limestone neutralization AMD.