1.2.2. Characteristics of Buccinum tenuissimum shell biomass

X-ray powder diffraction (XRD) patterns of the four kinds of Buccinum tenuissimum shell biomass samples are shown in Fig. 7. The crystal structure of the shell biomass was transformed from aragonite (CaCO3) into calcite (CaCO3) phase by heat-treatment (480°C, 6h). Moreover, the crystal structure of the shell biomass was mainly transformed into calcium oxide (CaO) by heat-treatment (950°C, 6h); and was mainly into calcium hydroxide (Ca(OH)2) by adding water after heat-treatment (950°C, 6h). SEM pictures of the four kinds of sieved shell biomass samples are shown in Fig. 8. Comparing Fig. 8(b) with Fig. 8(a), comparatively clear crystal with a lot of big particles may be observed by heat-traetment (480°C, 6h). It is suggested that ground original sample contains a lot of organic materials such as protein, and most of organic matter seem to disappear by heat-traetment. Moreover, fine crystal particle is not observed in Fig. 8 (c). This may be attributable to the phenomena that many crystals were connected largely with each other due to high-temperature sintering. Meanwhile, relative clear crystal (sizes are mostly 1.0-4.0pm) is observed in Fig. 8 (d).

(a)

(b)

(c)

(a) (b)

Furthermore, the measurement of specific surface area of the four kinds of sieved samples was performed in this study; and the results are shown in Table 6 along with the main crystal structure of these samples. Remarkably decrease of specific surface area (i. e., from 3.32m2/g to 0.390m2/g for BET, or from 5.35 m2/g to 0.612 m2/g for Langmuir) was found after heat-treatment (480°C, 6h). It is suggested that the crystal structure transformation (i. e., from aragonite (CaCO3) into calcite (CaCO3) phase) and also the difference of the surface morphology can be closely related to the remarkable decrease of specific surface area of the shell biomass. On the other hand, the surface area of "heat-treatment (950°C, 6h) sample" was 1.88m2/g for BET or 3.10m2/g for Langmuir respectively; and that of "heat-treatment (950°C, 6h) and water added sample" was 6.37m2/g for BET or 9.91m2/g for Langmuir, respectively.