Characterization of clay and nanoclay extracted from a semi-arid Vertisol and investigation of their carbon sequestration potential.

ABSTRACT

Mitigation of global climate change by means such as soil carbon (C) sequestration has become an important area of research. Soil organic matter (SOM) that is stabilized with clay minerals is the most persistent in soils. Currently, little is known regarding the C sequestration ability of nanoclay extracted from Vertisols in semi-arid regions. Therefore, the aim of this study was to extract and characterize nanoclay and bulk clay from a Vertisol from Iran, in terms of physicochemical surface properties and resistance of SOM to chemical oxidation. The clay fractions were studied before and after H2O2 treatment by total C analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), pyrolysis gas chromatography mass spectrometry (GC-MS), Fourier transform infrared (FTIR) spectroscopy, specific surface area analysis, and zeta potential. TEM and SEM images showed that the diameter of the extracted nanoclays was 16-46 nm and their morphology was more porous than bulk soil clay. The nanoclay had a much greater specific surface area (111.9 m2 g-1) than the bulk clay (67.9 m2 g-1). According to total C, FTIR, and zeta potential results, the nanoclay was enriched with 1.4 times more C than the bulk clay after peroxide treatment, indicating enhanced soil C stabilization in the nanoclay. About 45% of the peroxide-resistant SOM in the nanoclay was associated with N-containing compounds, indicating that these compounds contribute to SOM stability. The results demonstrate important role of nanoclay in soil C sequestration in Vertisols.