Potential Application of Oyster Shell as Adsorbent in Vegetable Oil Refining

Aim: The shell of invertebrate such as oyster has a very high potential in removing color pigments and other impurities in water and vegetable oils. However, application of such materials is receiving low attention both in industry and academia. This work studied the effectiveness of oyster shell as adsorbent in vegetable oil refining, in order to utilize its adsorption potential and to control the disposal effects of oyster shell on the environment.

Methodology: Activated and un-activated oyster shells were produced and used as adsorbent in the bleaching process of Palm Kernel Oil (PKO). The micro-structural images of the adsorbents produced were studied using Scanning Electron Microscope (SEM). The physicochemical properties of PKO before and after the bleaching process were monitored and compared. The performance evaluation of the adsorbents was further evaluated using Freundlich and Langmuir adsorptions isotherms.

Results: SEM images showed a clear difference in their morphology, on visual observation. The physicochemical properties after adsorption bleaching showed that the calcined oyster shell has more adsorptive power in its natural form than when activated with H2SO4. A maximum of 96.97 and 94.44 percentage color reductions were achieved for un-activated and activated oyster shells, respectively. K and n values of 0.397 and 0.567 were obtained for the un-activated adsorbents while 12.373 & -0.459 were obtained for the activated adsorbents respectively. The free fatty acid (3.38% of the PKO reduced to 3.37%, 2.21% and 3.22% with the use of crude, uanactivated and activated oyster shells, respectively. Similarly, the iodine value (16.6 mg/g) of the PKO reduced to 16.5, 13.69 and 16.49 mg/g with the use of crude, uanactivated and activated oyster shells, respectively Reduction were also observed in the percentage free fatty acid and iodine value after the adsorption process with both adsorbents but more reduction were noted in the PKO refined with un-activated oyster shell.

Conclusion: Oyster shell can be effectively used as adsorbent in vegetable oil refining. These results confirmed the effectiveness of the oyster shell in color and particulate removal.