2.2. Preparation of the hydrophobic spherical CaCO3 particles
The procedure employed for the preparation of CaCO3 was as follows.
10 g calcium oxide (CaO) was digested in 100 mL distilled water
to form a calcium hydroxide (Ca(OH)2) slurry, which was kept for
12 h at least. The slurry was filtered through a 150 mesh sieve in
order to get rid of the impurity and large particles. The ethanol solution
of DDPwas added into the slurry. The mixturewas stirred vigorously for
1 h at 40 °C. Then the premixed CO2 and N2 with molar ratio of 3:10
were bubbled into the slurry through a column. The reaction should
be stopped as soon as the pH value of the suspension decreased to 7.0.
The obtained CaCO3 precipitates were rinsed firstlywith anhydrous ethanol
and hot distilledwater three times, respectively. Lastly, the product
was dried for at least 24 h in an oven at approximate 80 °C.