## 3 Results and Discussion  
### FESEM/EDX and BET Analyses of CaCO\({}_{3}\) Particles Using Different Parameters  
Figure 2 indicates the effect of different volumes of DDW on the morphology of the CaCO\({}_{3}\) derived from cockle shells. Samples of CaCO\({}_{3}\) prepared by diluting CaCl\({}_{2}\) with 50 mL of DDW, as shown in Figure 2d, exhibited spherical-like, well-dispersed crystals with even size. However, other samples of CaCO\({}_{3}\) prepared with different DDW volumes exhibited clumped and agglomerated masses of crystals with irregular shapes and sizes. It may be explained that an increased amount of DDW resulted in greater dilution of samples, which provided more space for the movement of nanoparticles. However, as the volume of DDW increased, these molecules tended to be more solvated due to excess absorption of water, thus increasing in size and leading to agglomeration. Calcium carbonate prepared using 50 mL of DDW dilution had an average particle size of 39 nm, which was smaller in comparison to other samples. BET surface area analysis also revealed that using 50 mL of DDW gave the largest surface area and the smallest pore diameter of CaCO\({}_{3}\) in comparison to other samples, as shown in Table 1. The smaller particle size is related to a larger surface area and smaller pore diameter. CaCO\({}_{3}\), with various morphologies, have been fabricated previously. This has included cubic and needle shaped particles [36] where polyacrylamide was used, and rod-shaped particles [6] where a microemulsion system was used. Figure 1: Schematic diagram of CaCO\({}_{3}\) and CaO synthetic procedure. The morphology of CaCO\({}_{3}\) using the different polar solvents methanol, ethanol, and propanol is illustrated in Figure 3. The particle size and average pore diameter of CaCO\({}_{3}\) are tabulated in Table 2, where CaCO\({}_{3}\) particles, in all solvent systems except ethanol, possessed macroporous structure with a range of more than 50 nm, which is in accordance with [PERSON] et al. [37]. From the FESEM images, the samples prepared with ethanol displayed spherical calcite crystals, which were evenly dispersed and more symmetrical in structure when compared to methanol and propanol. The use of ethanol slowed down the chemical reaction, and hence the particles acquired a spherical shape with no agglomeration. Ethanol was used in other studies [38; 39] and showed similar results with the current study. This phenomenon is probably due to the presence of smaller and more active -OH and -C\({}_{2}\)H\({}_{5}\) groups in ethanol, which is reported to be effective in eliminating water molecules [40] that cause more agglomeration to form larger molecules [39]. The enhancement of the particle size upon the addition of ethanol was reported to be due to the reduction of the energy of atomization as a consequence of the decrease in the vapour pressure of the solution, owing to their slow evaporation [41; 42]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Volume of DDW (mL)** & **Surface Area (m\({}^{2}\)/g)** & **Average Pore Diameter (Å)** \\ \hline
0 & 8.53 & 386 \\
10 & 14.9 & 235 \\
20 & 16.8 & 281 \\
50 & 26.0 & 180 \\
60 & 25.0 & 183 \\
70 & 25.8 & 192 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Brunauer–Emmett–Teller (BET) average surface area, pore diameter of CaCO\({}_{3}\) in different volumes of double-distilled water (DDW). Figure 2: FESEM images of CaCO\({}_{3}\) at different volumes of distilled water: (**a**) 0 mL; (**b**) 10 mL; (**c**) 20 mL; (**d**) 50 mL; (**e**) 60 mL; and (**f**) 70 mL. The effect of the K\({}_{2}\)CO\({}_{3}\) feeding rate on the morphology of CaCO\({}_{3}\) nanoparticles in ethanolic solution is shown in Figure 4. It can be seen that the 1 h feeding rate of K\({}_{2}\)CO\({}_{3}\) had led to the formation of spherical CaCO\({}_{3}\) with clear surface and high sphericity. However, as the feeding rate was increased, the shape of the particles was distorted and their form changed with more agglomeration of the particles.