Preparation of TA-Coated CaCO3 as Slow-Release CO2 Gas Fertilizers

In a typical procedure,¹⁷ 2 g of PSS-doped CaCO₃ microspheres as mentioned above were dispersed in 200 mL of Tris-HCl buffer (50 mM, pH 8.0) containing 1.0 mg mL^–1 TA. After gently stirring at room temperature for 2 h, the microspheres were collected by centrifugation and washed with water three times. The fertilizers were dried to a constant weight under vacuum at 40 °C, and the resulting products were obtained. To get PSS-doped CaCO₃ with different thicknesses of TA-coated, the number of deposition cycles was designed at 1, 2, 3, 5, and 10, respectively. The deposition procedure was repeated in the same way as mentioned above. The resulting products are denoted as PTA-1, PTA-2, PTA-3, PTA-5, and PTA-10 where 1, 2, 3, 5, and 10 refer to the number of deposition cycles.