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Activated carbon from olive kernels in a two-stage process: Industrial improvement

Zabaniotou, A., Stavropoulos, G., Skoulou, V.
Bioresource technology 2008 v.99 no.2 pp. 320-326
activated carbon, adsorption, atmosphere, carbon dioxide, methylene blue, micropores, olives, processing stages, pyrolysis, seeds, steam, surface area, temperature, Belgium, United Kingdom
Activated carbons have been prepared from olive kernels and their adsorptive characteristics were investigated. A two stage process of pyrolysis-activation has been tested in two scales: (a) laboratory scale pyrolysis and chemical activation with KOH and (b) pilot/bench scale pyrolysis and physical activation with H₂O-CO₂. In the second case, olive kernels were first pyrolysed at 800°C, during 45min under an inert atmosphere in an industrial pyrolyser with a throughput of 1t/h (Compact Power Ltd., Bristol, UK). The resulting chars were subsequently activated with steam and carbon dioxide mixtures at 970°C in a batch pilot monohearth reactor at NESA facility (Louvain-la Neuve, Belgium). The active carbons obtained from both scales were characterized by N₂ adsorption at 77K, methyl-blue adsorption (MB adsorption) at room temperature and SEM analysis. Surface area and MB adsorption were found to increase with the degree of burn-off. The maximum BET surface area was found to be around 1000-1200m²/g for active carbons produced at industrial scale with physical activation, and 3049m²/g for active carbons produced at laboratory with KOH activation. The pores of the produced carbons were composed of micropores at the early stages of activation and both micropores and mesopores at the late stages. Methylene blue removal capacity appeared to be comparable to that of commercial carbons and even higher at high degrees of activation.