Metz Rouven, Kumar Naresh, Schenkeveld Walter D C, Obst Martin, Voegelin Andreas, Mangold Stefan, Kraemer Stephan M
Centre for Microbiology and Environmental Systems Science, Department for Environmental Geosciences, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria.
Soil Chemistry, Wageningen University and Research, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands.
Environ Sci Technol. 2024 Aug 16;58(34):15321-32. doi: 10.1021/acs.est.4c04809.
The interest in the mineral vivianite (Fe(PO)·8HO) as a more sustainable P resource has grown significantly in recent years owing to its efficient recovery from wastewater and its potential use as a P fertilizer. Vivianite is metastable in oxic environments and readily oxidizes. As dissolution and oxidation occur concurrently, the impact of oxidation on the dissolution rate and mechanism is not fully understood. In this study, we disentangled the oxidation and dissolution of vivianite to develop a quantitative and mechanistic understanding of dissolution rates and mechanisms under oxic conditions. Controlled batch and flow-through experiments with pristine and preoxidized vivianite were conducted to systematically investigate the effect of oxidation on vivianite dissolution at various pH-values and temperatures. Using X-ray absorption spectroscopy and scanning transmission X-ray microscopy techniques, we demonstrated that oxidation of vivianite generated a core-shell structure with a passivating oxidized amorphous Fe(III)-PO surface layer and a pristine vivianite core, leading to diffusion-controlled oxidation kinetics. Initial (<1 h) dissolution rates and concomitant P and Fe release (∼48 h) decreased strongly with increasing degree of oxidation (0-≤ 100%). Both increasing temperature (5-75 °C) and pH (5-9) accelerated oxidation, and, consequently, slowed down dissolution kinetics.
近年来，由于可以从废水中有效回收且有作为磷肥的潜在用途，对矿物蓝铁矿（Fe₃(PO₄)₂·8H₂O）作为一种更具可持续性的磷资源的关注度显著提高。蓝铁矿在有氧环境中是亚稳态的，容易氧化。由于溶解和氧化同时发生，氧化对溶解速率和机制的影响尚未完全了解。在本研究中，我们将蓝铁矿的氧化和溶解过程分开，以定量和机理的方式理解有氧条件下的溶解速率和机制。对原始和预氧化的蓝铁矿进行了控制批次和流通实验，以系统研究在不同pH值和温度下氧化对蓝铁矿溶解的影响。使用X射线吸收光谱和扫描透射X射线显微镜技术，我们证明蓝铁矿的氧化产生了一种核壳结构，其钝化的氧化非晶态Fe(III)-PO表面层和原始的蓝铁矿核心，导致扩散控制的氧化动力学。随着氧化程度的增加（0 - ≤100%），初始（<1小时）溶解速率以及伴随的磷和铁释放（约48小时）都大幅下降。温度（5 - 75°C）和pH值（5 - 9）的升高都加速了氧化，因此减缓了溶解动力学。
