Sulfur/sodium bentonite mixtures as sulfur fertilizers. 1. The effects of S/Na-bentonite ratios on the rate of dispersion and particle size distribution of elemental sulfur dispersed from laboratory-produced prills

Sulfur/sodium bentonite fertilizer prills were made by blending between 5 and 40% by weight of a swelling sodium bentonite clay with molten sulfur (S) and chilling droplets of the mixtures in oil. The resulting prills were hard and dust free and thus offered a suitable form for elemental sulfur (S°) transportation and application. The prills were stable at normal room temperature and RH. Prill strength was much reduced by prolonged storage at 80% RH. With 15% or more bentonite the bulk resistivity was sufficiently low that no electrostatic charge build-up was likely and consequently there was little risk of spontaneous combustion.Prills containing 10% or more bentonite disintegrated when placed in water and both the rate of dispersion and the fineness of the dispersed S° particles increased bentonite content. Bentonite contents of 15–20% appeared to offer the best combination of rapid prill dispersion, fine dispersed S° particle size, and high S° content.