Kinetics of the Growth of Sulfur Nanoparticles during Their Precipitation from Aqueous Solutions of Calcium Polysulfide

Calcium polysulfide solutions prepared from mechanically activated sulfur are used for the chemical precipitation of sulfur nanoparticles (nanosulfur) in an aqueous environment and on various substrates. The precipitated nanoparticles are characterized using a laser particle size analyzer by X-ray diffraction, optical microscopy, and infrared and ultraviolet spectrometry. It is found that an orthorhombic nanosulfur phase of a spherical morphology with an average size of 20 nm is synthesized from calcium polysulfide in an aqueous environment; over time, it enlarges to micrometer sizes at a rate that increases with increasing temperature. The kinetic laws governing the growth of nanosulfur are first determined. It is found that the precipitation of a calcium polysulfide solution on a glass substrate leads to a uniform distribution of nanosulfur in the form of droplets with an average size of 2 μm, which are transformed into crystals during drying. The passing of carbon dioxide through a calcium polysulfide solution leads to the coprecipitation of a sulfur nanocomposite with calcium carbonate in the calcite and witherite phases. The treatment of the porous surface of aerated concrete with nanosulfur leads to the formation of a stable coating of hydrophobic sulfur, which hinders the penetration of water deep into the material.