Synthesis of foliar and Ca‐S‐Si compound fertilizers from titanium‐bearing blast furnace slag

The synthesis of foliar and Ca‐S‐Si compound fertilizers using titanium‐bearing blast furnace slag, potassium bisulfate, citric acid, carbamide, and magnesia as raw materials is reported for the first time. This synthesis enhances the solubility of the slag and transforms the nutritional elements into such forms as to be more readily absorbed by plants. The effects of the process conditions on the dissolution rates of iron, titanium, and magnesium were investigated through the experiment. The results showed that the optimal synthesis process conditions for foliar fertilizer are 560°C for 12 min, with the mass ratio of potassium bisulfate to titanium‐bearing blast furnace slag at 6:1. Under these conditions, more than 85% of the iron, titanium, and magnesium in the slag were converted into water‐soluble species in the foliar fertilizer. Foliar fertilizer with a pH of 6 contained such nutritional elements as nitrogen, sulfur, potassium, iron, titanium, and magnesium, which can all be effectively absorbed by plants. The Ca‐S‐Si compound fertilizer was primarily composed of calcium silicate (soluble in citric acid solution) and calcium sulfate (slightly soluble in water). The application of foliar fertilizer and Ca‐S‐Si fertilizer increased the yield of castor‐oil plants by 35.3% and 21.3%, respectively. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1316–1321, 2014