Weathering of Silver Hill Illite by Li-Oxalate at pH 8.

Clay minerals in the rhizosphere are subject to the presence of organic exudates from plant roots and microorganisms.  Silver Hill illite particles (sized 0.1 to 1µm) were treated with 0.01 and 0.1 M Li-oxalate at pH 8 and 60º C to create an accelerated weathering environment. Lithium chloride treatments as well as untreated illite were used as controls. Chemical analysis of the supernatant did not show selective weathering of aluminum from the illite and did not show a difference between chloride-treated and oxalate-treated samples. X-ray diffraction (XRD) analysis patterns of all samples were analyzed with MudMaster, software that utilizes the Bertaut-Warren-Averbach method to determine crystalline strain and sizes of mineral particles.  The fundamental illite particle thickness decreased, indicating fewer numbers of 2:1 layers per particle.  Increased strain after reaction with oxalate indicated that weathering was not uniform throughout the particle. Image analysis of atomic force micrographs with GIS showed higher surface area, volume, thickness, and diameter for the untreated particles compared to both LiCl and Li-oxalate (LiOx) treated illite.  The AFM analysis also showed a reduction in the average number of layers per particle for both LiCl and LiOx treated samples compared to the untreated illite.