**3.2 Performance of methylene blue removal**

The removal of MB was carried out under UV illumination for 150 min, the photocatalytic efficiency of the composite photocatalyst was determined and the result is shown in **Figure 4**. When the cockle and mussel shell was used as an adsorbent, there was no photocatalytic degradation of the MB solution, which was as expected (**Figure 4a**). By comparison of the composite photocatalyst, mussel shell/TiO2 exhibited the highest adsorption and achieved 25.92% of MB photocatalytic degradation compared to cockle shell/TiO2 (**Figure 4b** and **c**). It is interesting to note that the particle size of the mussel shell/TiO2 composite photocatalyst is smaller than cockle shell/TiO2, which gives a higher surface area for adsorption and photocatalytic activity takes place.
