The formation of trace metal rich minerals in soils is one pathway by which contaminants can be removed from the soil solution to inhibit further metal transport. The newly formed precipitates are important for remediation efforts of contaminated soils and in the modeling of natural geochemical cycling in sediments. Trace metal rich layered double hydroxides (LDHs) serve as an environmentally important example in contaminated soils, and they also have a variety of applications in materials science. Their formation in soils occurs at the mineral-water interface, can be kinetically rapid, and the reaction products can have solubility product constants lower than pure metal hydroxides. Though, there are few kinetic data obtained in real-time and at the molecular scale which identify precipitate formation. Our objective is to determine in real-time and at the molecular scale the kinetics and speciation of nickel (Ni) sorption on aluminium (Al)-rich clay minerals utilizing Quick-EXAFS spectroscopy. We hypothesized that LDHs would form in less than several hours in a phyllosilicate mineral system using a custom-built flow cell. Additionally, we employed wavelet transformation (WT) to help distinguish between LDH phases and single metal hydroxide phases. Using WT we provide evidence that nitrate or carbonate groups may remain adsorbed to the hydroxide interlayer, and those groups may appear as lighter backscattering components in the EXAFS spectra, producing a similar effect as Al in the WT plot. We report real-time

Quick-EXAFS data which illustrate the rapid formation of Ni-Al LDH precipitates at the phyllosilicate mineral–water interface in a flow environment in as little as 31–40 min. These real-time data enhance our understanding of the kinetics of mineral–water interface processes, such as adsorption, dissolution, and precipitation, by illustrating their rapid and simultaneous occurrence in a dynamic environment and showing that precipitation and adsorption can occur on the same rapid timescale.