Collaborative Research: Thermodynamic Properties of Solutions Generated by Acid Rock Drainage: Fe2O3-SO3-H2O systems

金属硫化物矿物的氧化可以产生pH值低至-3.6的溶液，每升溶液中含有的水少于190克。在任何硫化物暴露于风化过程的地方，包括矿山作业和废物、暴露的沿海沉积物和暴露的古代海相沉积岩，都可能产生这种酸性岩石排水。这些解决方案对环境的影响很大，仅在北美就造成了数十亿美元的损失。酸性岩石排水也产生了大型矿床，使铜和其他金属从浸染矿化中经济回收成为可能，并孕育了一些不寻常的微生物群落。对这些系统的化学成分进行精确建模的能力将极大地有助于修复环境敏感地点的努力，提高湿法冶金工艺对金属的回收，并更好地了解控制酸性岩石排水化学成分日变化和季节变化的过程。这种详细的建模目前对许多系统是不可能的：强酸性硫酸铁盐水缺乏活度系数，以及有效模拟水和矿物物种所需的一些基本平衡常数。这个项目将采取三个步骤来消除其中的一些障碍。1)测定硫酸铁和混合硫酸铁-亚铁盐水的渗透系数。将对数据进行建模，以检索使用特定离子相互作用模型计算活度系数所需的相互作用参数。2)硫酸铁配合物的缔合常数将使用汞/硫酸亚汞浓度池测量。这些关联常数对于完成活动建模是必需的。黄钾铁矾的溶解度将在一定温度和离子强度范围内以及在不同的离子介质中测量。该研究将显著提高天然硫酸酸性水体的准确建模能力。

0230172Ridley The oxidation of metal sulfide minerals can generate solutions that have pH values as low as -3.6 and contain less than 190 g H2O per liter of solution. Such acid rock drainage can be generated in any locality where sulfides are exposed to the weathering process, including mine workings and wastes, exposed coastal sediments, and exposures of ancient marine sedimentary rocks. These solutions have a high environmental impact that is estimated to be in the billions of dollars in North America alone. Acid rock drainage has also generated large ore deposits, makes possible the economic recovery of copper and other metals from disseminated mineralization, and hosts some unusual microbial communities. The ability to model the chemistry of these systems accurately would aid greatly in efforts to remediate environmentally sensitive sites, improve the recovery of metals by hydrometallurgic processes, and better understand the processes that control diurnal and seasonal variations in the chemistry of acid rock drainage. Such detailed modeling is currently impossible for many systems: activity coefficients are lacking for strongly acidic ferric sulfate brines as are some basic equilibrium constants needed to model the aqueous and mineral species effectively. This project will take three steps to remove some of those obstacles. 1)Osmotic coefficients of ferric sulfate and mixed ferric-ferrous sulfate brines will be measured. The data will be modeled to retrieve interaction parameters necessary to calculate activity coefficients using the specific ion interaction model. 2)The association constants for ferric sulfate complexes will be measured using a mercury/mercurous sulfate concentration cell. These association constants will be necessary to complete the activity modeling. 3)The solubility of jarosite will be measured over a range of temperatures and ionic strength and in different ionic media. This research will improve significantly the ability to accurately model natural acid-sulfate waters.