A novel potassium fertilizer material is obtained via hydrothermal processing of K-feldspar ore in alkaline conditions.

Solvent extraction (SX) is an important separation method with countless applications in the chemical industry. The water/oil interface is an essential feature of SX systems. Microfluidic technology is ideally suited for exploitation in SX due to intrinsic advantages of the micro dimensions that result in laminar flow conditions, high surface-to-volume ratio and the reduced chemical quantities needed. This review describes the use of microfluidic devices in SX.

The mining of soluble potassium salts (potash) is essential for manufacturing fertilizers required to ensure continuous production of crops and hence global food security. As of 2014, potash is mined predominantly in the northern hemisphere, where large deposits occur. Production tonnage and prices do not take into account the needs of the farmers of the poorest countries. Consequently, soils of some regions of the southern hemisphere are currently being depleted of potassium due to the expansion and intensification of agriculture coupled with the lack of affordable potash. Moving away from mined salts towards locally available resources of potassium, such as K-bearing silicates, could be one option to improve this situation. Overall, the global potash production system and its sustainability warrant discussion. In this contribution we examine the history of potash production, and discuss the different sources and technologies used throughout the centuries. In particular, we highlight the political and economic conditions that favored the development of one specific technology over another. We identified a pattern of needs driving innovation. We show that as needs evolved throughout history, alternatives to soluble salts have been used to obtain K-fertilizers. Those alternatives may meet the incoming needs of our century, providing the regulatory and advisory practices that prevailed in the 20 th century are revised.

Growth of world population and consequent growth of food demand drives expansion and intensification of agriculture. High-yield agriculture relies on fertilizers that, therefore, become a key focus to address concerns on global food security. Currently, potassium fertilizers are produced in the northern hemisphere. These fertilizers do not suit the deep leached soils of tropical countries, partly due to their high solubility. The use of geological materials (agrominerals) such as K-bearing silicates could be an option to develop slow-release potassium fertilizers from abundant and readily available geologic sources. Thus far, both laboratory and agronomic field tests on such materials have been inconclusive, meaning that a clear relationship between the application of agrominerals to soil and the fertilizing effect could not be established. Novel interdisciplinary approaches are needed to predict the release of nutrients from agrominerals. This study presents one such approach, proposing a detailed analysis of the relationship between petrographic characteristics of twelve samples of ultrapotassic syenite (K-feldspar ore), and the leaching of potassium from their powders. The correlation between petrographic features, comminution and leaching proposed here, is expected to play a major role in the assessment of the fertilizing properties of agrominerals in the field.

One of the key Sustainable Development Goals (SDG) set by the United Nations (UN) aims by 2030 to "end hunger, achieve food security and improved nutrition and promote sustainable agriculture". Fertilizers will play a pivotal role in achieving that goal given that ~90% of crop production growth is expected to come from higher yields and increased cropping intensity. However, materials-science research on fertilizers has received little attention, especially in Africa. In this work we present an overview of the use of fertilizers in Africa to date, and based on that overview we suggest future research directions for material scientists. Developing a new generation of local and affordable fertilizers will launch Africa into a new phase of remunerative agricultural production that in turn will lead to both food self-sufficiency and considerable progress towards goals of food and nutrition security.

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The diffusion behaviour of Co(II) ion in an aqueous homogeneous system and that of 8-hydroxyquinoline (8HQ) in a heterogeneous liquid-liquid system was measured in a Y-Y shaped microfluidic device. We propose a modified version of a previously published equation for a static system to describe the diffusion behaviour of chemical species in this microfluidic device. Specific adaptations of the original equation to the micro environment are illustrated and discussed. The model proposed successfully fitted the diffusion of Co(II) in a homogeneous system (aqueous solutions) and 8HQ across a water/oil interface. We envisage the application of the proposed equation for the discrimination of the diffusion contribution in solvent extraction kinetic studies.

The rate of K+ leaching from soil minerals such as K-feldspar is believed to be too slow to provide agronomic benefit. Currently, theories and methods available to interpret kinetics of mineral processes in soil fail to consider its microfluidic nature. In this study, we measure the leaching rate of K+ ions from a K-feldspar-bearing rock (syenite) in a microfluidic environment, and demonstrate that at the spatial and temporal scales experienced by crop roots, K+ is available at a faster rate than that measured with conventional apparatuses. We present a device to investigate kinetics of mineral leaching at an unprecedented simultaneous resolution of space (~101-102 μm), time (~101-102 min) and fluid volume (~100-101 mL). Results obtained from such a device challenge the notion that silicate minerals cannot be used as alternative fertilizers for tropical soils.