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The use of Greek low rank coals for mitigating environmental problems

Pasadakis Nikos, Triantafyllou Georgios, Papanikolaou C. , Foskolos Antonis

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Summary

Twenty eight Greek low rank coals (peat, peaty lignites, lignites of both matrix and xylite-rich lithotypes, and subbituminous coals) were physically activated by pyrolysis in order to in-crease their adsorptive surface area. Results show that the surface area of acti-vated Greek low rank coal (lignite) samples in-creased substantially and in some cases more than that of commercial products. The increase in surface area was higher for higher carbon content and for lower the ash content. The adsorption capacity of activated coals for NO, SO2 C3H3 and a mixture of light hydrocar-bons (CH4, C2H6, C3H8 and C4H10) at various temperatures, as well as the adsorption of phe-nols and the decrease of COD (Chemical Oxy-gen Demand) in olive oil mill waste disposals was measured in selected samples. For the gases the results show a positive cor-relation between the surface area and the gas ad-sorption. In contrast, the gas adsorption is in-versely correlated with temperature. The maxi-mum recorded adsorbed values are: NO = 8.22 x 10-5 mol/g at 35 oC; SO2 = 38.65 x 10-5 mol/g at 60 oC; C3H6 = 38.9 x 10-5 mol/g at 35 oC: and light hydrocarbons = 19.24 x 10-5 mol/g at 35 oC; The long chain hydrocarbons are prefer-entially adsorbed on activated lignites as com-pared to the short chain hydrocarbons. The maximum recorded adsorption of phenol was 30.6 mg/g of activated lignite, while the commercial one (HOK) adsorbed 16mg/g of ac-tivated lignite. The COD reduction was 1262 mg of COD/g of activated lignite while in the commercial one the reduction was 439 mg of COD/g of activated lignite. The results also suggest a positive correlation between the surface area and the content of the telohuminite maceral subgroup above the level of 45%.

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