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Adsorption of copper on olive pomace activated biochar

Deligianni Christina

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Summary

The main objective of the dissertation is the adsorption of copper Cu (II) from an aqueous solution to biochar from olive pit. Experiments were conducted using not only the entire olive pit, but also using separately its kernel and pulp, all of which were pyrolyzed at 400 oC. In addition, the adsorption of copper on biochar (whole, kernel, pulp) after treatment with potassium hydroxide (KOH) and zinc chloride (ZnCl2) at 800 oC was studied. All pyrolyzed samples were characterized in terms of pH, ash content, elemental composition, metal determination, specific surface area (BET) and spectroscopy (FTIR). The unprocessed materials were also characterized in reference to their moisture content, volatile mater content and permanent carbon content. A series of adsorption experiments were then performed, which showed that the materials treated with KOH and ZnCl2 were not effective in adsorbing Cu (II). Subsequently, kinetic adsorption experiments of copper Cu (II) were performed only on non-chemically treated biochars. The results showed that the olive pulp biochar worked significantly better for copper adsorption and thus, the Cu (II) copper adsorption equilibrium experiments were only conducted for the pulp biochar. In total, the effect of four factors was studied, namely pH, contact time, temperature and Cu (II) concentration in the solution.The biochars showed both positive and negative influence on all the examined factors, as well as slightly different behavior, due to their different composition. In addition, 6 models were applied to process the results of the kinetic and the adsorption equilibrium experiments. More specifically, pseudo-first order, pseudo-second order and intraparticle diffusion models were applied for the kinetic experiments and linear isotherm, Freundlich isotherm and Langmuir isotherm models were applied for the absorption equilibrium experiments. The models that most satisfactorily describe the materials studied are the pseudo-second order model for the kinetic experiments and the Freundlich and Langmuir isotherm models in combination for the adsorption equilibrium.In conclusion, the material that showed the best results was the pulp, which was pyrolyzed at 400 oC without further chemical treatment and specifically treated at pH 6, with a contact time of 4 hours, temperature 45 ° C and for 10 mg / L copper CU (II) concentration in the solution.

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