Preparation of activated carbon from Tunisian olive-waste cakes and its application for adsorption of heavy metal ions

The present work explored the use of Tunisian olive-waste cakes, a by-product of the manufacture process of olive oil in mills, as a potential feedstock for the preparation of activated carbon. Chemical activation of this precursor, using phosphoric acid as dehydrating agent, was adopted. To optimize the preparation method, the effect of the main process parameters (such as acid concentration, impregnation ratio, temperature of pyrolysis step) on the performances of the obtained activated carbons (expressed in terms of iodine and methylene blue numbers and specific surface area) was studied. The optimal activated carbon was fully characterized considering its adsorption properties as well as its chemical structure and morphology. To enhance the adsorption capacity of this carbon for heavy metals, a modification of the chemical characteristics of the sorbent surface was performed, using KMnO4 as oxidant. The efficiency of this treatment was evaluated considering the adsorption of Cu2+ ions as a model for metallic species. Column adsorption tests showed the high capacity of the activated carbon to reduce KMnO4 into insoluble manganese (IV) oxide (MnO2) which impregnated the sorbent surface. The results indicated also that copper uptake capacity was enhanced by a factor of up to 3 for the permanganate-treated activated carbon