INFEWS N/P/H2O: Chemical and structural transformations at low solubility magnesium mineral-wastewater interface during struvite formation and growth

在这个由化学系环境化学科学项目资助的项目中，Jonas Baltrusaitis教授和他的学生研究了含镁的低溶解度矿物表面与来自模拟废水流的水铵和磷酸盐离子的反应。目标是开发新的，高效的氮(N)和磷(P)固定路线，利用这些矿物质作为缓释肥料。该项目利用现成的含镁矿物（如氧化镁、碳酸镁、白云石和蛇纹岩）作为目前使用的低丰度、高溶解度的氯化镁和硫酸镁的替代品。这项工作的结果有望通过提供对矿物表面化学的基本理解来指导养分回收和再循环系统的发展。因此，该项目解决了在食物、能源和水的关系中充分管理营养物质的关键挑战。该项目为表面科学和环境催化领域的研究生和本科生提供培训机会。此外，首席研究员通过利哈伊大学暑期工程学院和暑期选择工程营积极参与促进当地社区对环境科学研究的理解。本项目使用光谱技术研究单晶表面上扩散受限条件下的反应性表面中间体和产物。这提供了详细的反应动力学，固体表面转化和生长机制的信息，以及对反应位点性质的见解。在实验室合成了铁和钙掺杂的氧化镁纳米颗粒。在界面限制条件下，从水溶液中吸附铵盐和磷酸盐离子，以监测鸟粪石或羟基磷灰石等养分缓释肥料矿物的生长。利用拉曼光谱和漫反射红外光谱对模型镁矿物表面及其生长和吸附进行了表征。利用x射线光电子能谱和高分辨率透射电子显微镜对合成的MgO纳米颗粒的结构表面细节进行了研究。用离子色谱法测定了含铵、磷酸盐模型废水中养分缓释肥料材料的生长动力学。

In this project funded by the Environmental Chemical Sciences program in the Division of Chemistry, Professor Jonas Baltrusaitis and his students study reactions of magnesium-containing, low solubility mineral surfaces with aqueous ammonium and phosphate ions from model wastewater streams. The goal is to develop new, highly efficient nitrogen (N) and phosphorus (P) immobilization routes for use of these minerals as slow release fertilizers. The project utilizes readily available magnesium-containing minerals (e.g., magnesium oxide, magnesium carbonate, dolomite and serpentinite) as substitutes for low abundance, high solubility magnesium chlorides and sulfates that are currently used. Outcomes of this work are expected to guide the development of nutrient recovery and recycling systems by providing fundamental understanding of mineral surface chemistry. Thus, this project addresses critical challenges of adequately managing nutrients at the nexus of food, energy and water. The project provides training opportunities for graduate and undergraduate students in the areas of surface science and environmental catalysis. Furthermore, the principal investigator actively participates in efforts to promote understanding of environmental science research in the local community via the Lehigh University Summer Engineering Institute and Summer CHOICES Engineering Camp.This project uses spectroscopic techniques to investigate reactive surface intermediates and products under diffusion-limited conditions on single crystal surfaces. This provides information on the detailed reaction kinetics, solid surface transformation and growth mechanisms, and insights into the nature of reactive sites. Iron- and calcium-doped MgO nanoparticles are synthesized in the laboratory. Ammonium and phosphate ion adsorption from aqueous solutions is performed to monitor the growth of slow nutrient release fertilizer mineral, such as struvite or hydroxyapatite, under interface limited conditions. Model magnesium mineral surfaces, their growth, and adsorption are characterized using Raman and diffuse reflectance infrared spectroscopy. Structural surface details of the synthesized MgO nanoparticles are interrogated using X-ray photoelectron spectroscopy and high resolution transmission electron microscopy. Growth kinetics of slow nutrient release fertilizer materials from ammonium and phosphate containing model wastewater solutions is measured using ion chromatography.