Release rates of phosphate from coated fertilizer through nano CaCO3-wax mixtures

Calcium phosphate fertilizer pellets coated with mixtures of wax and nano calcium oxide were studied for release rates of phosphate through the coating. The composition of the coating mixture has been of 0%, 20% and 30% nano-CaCO₃ by weight in the wax solution. The pellets were exposed to solutions of pH 4, pH 7 and pH 9.2 in a reactor in an experimental set-up. Trends of release rates with pH were investigated. Results show that increasing composition of nano-CaCO₃ in wax coating layer and decreasing of pH condition increased the nutrient transfer rate to the surrounding. The combination of different compositions of nano-CaCO₃ in wax coating layer showed possibilities to control the nutrient release rate and thus reducing the environmental pollution effect and enhance economic efficiency. Parameters with respect to a model fitting the experimental data were evaluated.