Resolving the mechanism(s) of iron(III) oxyhydroxide nucleation at pH 2.5 to pH 3.5

Iron(III) oxyhydroxide (FeOx) minerals play important roles in a wide range of natural and engineered aqueous systems. Their properties depend strongly on the chemical mechanisms governing their nucleation and subsequent transformation, however many details of these mechanisms remain unresolved. Recent studies have shown the existence of small oligomers under acidic conditions and suggested that FeOx formation may occur through non-classical nucleation pathways characterised by the formation of so-called prenucleation clusters (PNCs) that subsequently transform to yield FeOx minerals, but critical knowledge gaps remain about the processes involved. The aim of this proposed experiment is to characterise the structural evolution of FeOx from the atomic scale to the particle scale during FeOx nucleation and subsequent transformation at pH 2.5-3.5 using in situ time-resolved WAXS, SAXS and USAXS, thus helping to resolve critical questions about mechanisms of FeOx formation.