Fernández-Olmo Ignacio, Lasa Cristina, Irabien Angel
Departamento Ingeniería Química y Química Inorgánica, Universidad de Cantabria, Avda Los Castros s/n 39005, Santander, Spain.
J Hazard Mater. 2007 Jun 18;144(3):720-4. doi: 10.1016/j.jhazmat.2007.01.102. Epub 2007 Jan 30.
Equilibrium models which attempt for the influence of pH on the solubility of metals can improve the dynamic leaching models developed to describe the long-term behavior of waste-derived forms. In addition, such models can be used to predict the concentration of metals in equilibrium leaching tests at a given pH. The aim of this work is to model the equilibrium concentration of Zn from untreated and stabilized/solidified (S/S) electric arc furnace dust (EAFD) using experimental data obtained from a pH-dependence leaching test (acid neutralization capacity, ANC). EAFD is a hazardous waste generated in electric arc furnace steel factories; it contains significant amounts of heavy metals such as Zn, Pb, Cr or Cd. EAFD from a local factory was characterized by X-ray fluorescence (XRF), acid digestion and X-ray diffraction (XRD). Zn and Fe were the main components while the XRD analysis revealed that zincite, zinc ferrite and hematite were the main crystalline phases. Different cement/EAFD formulations ranging from 7 to 20% dry weight of cement were prepared and subjected to the ANC leaching test. An amphoteric behavior of Zn was found from the pH dependence test. To model this behavior, the geochemical model Visual MINTEQ (VMINTEQ) was used. In addition to the geochemical model, an empirical model based on the dissolution of Zn in the acidic zone and the re-dissolution of zinc compounds in the alkaline zone was considered showing a similar prediction than that obtained with VMINTEQ. This empirical model seems to be more appropriate when the metal speciation is unknown, or when if known, the theoretical solid phases included in the database of VMINTEQ do not allow to describe the experimental data.
考虑pH对金属溶解度影响的平衡模型可以改进为描述废物衍生形态长期行为而开发的动态浸出模型。此外，此类模型可用于预测给定pH下平衡浸出试验中金属的浓度。本工作的目的是利用从pH依赖性浸出试验（酸中和能力，ANC）获得的实验数据，对未处理和稳定化/固化（S/S）电弧炉粉尘（EAFD）中锌的平衡浓度进行建模。EAFD是电弧炉钢铁厂产生的危险废物；它含有大量重金属，如锌、铅、铬或镉。对当地一家工厂的EAFD进行了X射线荧光（XRF）、酸消解和X射线衍射（XRD）表征。锌和铁是主要成分，XRD分析表明，氧化锌、铁酸锌和赤铁矿是主要晶相。制备了水泥/EAFD干重从7%到20%不等的不同配方，并进行了ANC浸出试验。从pH依赖性试验中发现了锌的两性行为。为了对这种行为进行建模，使用了地球化学模型Visual MINTEQ（VMINTEQ）。除了地球化学模型外，还考虑了一个基于锌在酸性区域溶解和锌化合物在碱性区域再溶解的经验模型，该模型显示出与VMINTEQ获得的预测相似的结果。当金属形态未知时，或者当已知时，VMINTEQ数据库中包含的理论固相无法描述实验数据时，这个经验模型似乎更合适。
