Optimisation of phosphate loading on graphene oxide-Fe(iii) composites-possibilities for engineering slow release fertilisers

Current commercially available phosphorus (P) fertilisers, which are highly soluble salts, are susceptible to surface runoff to waterways, and leaching to groundwaters where soils are light/medium textured. Here, we report the synthesis of a graphene oxide (GO)/iron (GO–Fe) composite, a promising carrier for loading P. The GO–Fe carriers loaded with P acted as slow release fertilisers with tunable loading/release properties. The amount of P loaded onto the GO–Fe composite was 15%, similar to commercial products. Investigation of the morphology and spectroscopic and chemical analysis revealed a complex loading mechanism of Fe onto GO. Iron, as an active center for P sorption, could interact with the oxygen functional groups at the edge of GO sheets as well as the π-electron system of the aromatic part of GO. Column perfusion studies, visualisation of P diffusion in soils and chemical analysis of soils after diffusion showed the composites to have slow-release properties. Pot experiments using wheat and our composites resulted in the same yield as using highly soluble commercial fertiliser.Ivan B. Andelkovic, Shervin Kabiri, Rodrigo C. da Silva, Ehsan Tavakkoli, Jason K. Kirby, Dusan Losic and Michael J. McLaughli

Hydrogen-Helium Mixtures at High Pressure

The properties of hydrogen-helium mixtures at high pressure are crucial to address important questions about the interior of Giant planets e.g. whether Jupiter has a rocky core and did it emerge via core accretion? Using path integral Monte Carlo simulations, we study the properties of these mixtures as a function of temperature, density and composition. The equation of state is calculated and compared to chemical models. We probe the accuracy of the ideal mixing approximation commonly used in such models. Finally, we discuss the structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004