Embrapa Soils, Brazilian Agricultural Research Corporation - Embrapa, 22460-000 Rio de Janeiro, RJ, Brazil.
São Carlos Institute of Physics, University of São Paulo, PO Box 369, 13560-970 São Carlos, SP, Brazil; Centre for Membrane Separations, Adsorption, Catalysis and Spectroscopy for Sustainable Solutions (cMACS), Department of Microbial and Molecular Systems (M2S), KU Leuven, Leuven 3001, Belgium.
J Magn Reson. 2022 Sep;342:107264. doi: 10.1016/j.jmr.2022.107264. Epub 2022 Jul 8.
Caking is associated with the consolidation of dry powder and granules, leading to losses of function and/or quality. It has been object of studies in the pharmaceutical, food and fertiliser areas since 1920's because of its significant impact on product quality and value. Caking has been described as a three-step event consisting of sorption-dissolution-recrystallisation phases and constitutes a critical factor in fertilisers losses during storage while also hampering fertiliser application. Current methods for the evaluation of water sorption dynamics are expensive, time-consuming and/or inaccurate. This manuscript describes an unprecedented application of low-field H NMR relaxometry for the kinetic study of humidity uptake, in real-time, by urea mixed with different concentrations of an anti-caking agent (zeolite). The proposed method allows to follow the water uptake in different domains of the mixed fertiliser/zeolite samples. To our knowledge, this dynamic has not been observed and quantified so far in real-time. Furthermore, we presented the use of 2D-ILT for kinetic studies, being the first dimension the usual transverse relaxation and the second dimension the kinetic one. With this approach, the NMR relaxation times T correlated to time constants associated with the uptake kinetics of the water. This method could be extended to several kinetic studies and experiments with temperature variation. Depending on the kinetics of the studied process, the kernel of the Laplace transform must be suitably adapted.
结块与干粉和颗粒的固结有关，导致功能和/或质量损失。自 20 世纪 20 年代以来，由于其对产品质量和价值的重大影响，它一直是制药、食品和肥料领域的研究对象。结块被描述为一个由吸附-溶解-再结晶三个阶段组成的事件，是肥料在储存过程中损失的关键因素，同时也阻碍了肥料的施用。目前评估水分吸湿性动力学的方法既昂贵、耗时又不准确。本文描述了一种前所未有的应用，即低场 H NMR 弛豫法实时研究尿素与不同浓度的防结块剂（沸石）混合时的湿度吸收动力学。该方法允许在混合肥料/沸石样品的不同区域中跟踪水分的吸收。据我们所知，到目前为止，这种动态还没有在实时中被观察和量化。此外，我们还介绍了二维 ILT 在动力学研究中的应用，第一维是通常的横向弛豫，第二维是动力学弛豫。通过这种方法，与水吸收动力学相关的 NMR 弛豫时间 T 与时间常数相关联。该方法可以扩展到几个动力学研究和温度变化的实验中。根据所研究过程的动力学，拉普拉斯变换的核必须进行适当的调整。
