Cent. Eur. J. Eng. • 4(1) • 2014 • 90-99 DOI: 10.2478/s13531-013-0148-z Central European Journal of Engineering Valorization of agricultural waste into activated carbons and its adsorption characteristics for heavy metals Research Article Bachar Koubaissy 1∗ Joumana Toufaily 1 Safaa Cheikh 1 Malak Sayed Hassan 1 Tayssir Hamieh 12 1 Laboratory of Materials, Catalysis, Environment and Analytical Methods, Faculty of Sciences I, Lebanese University, Campus Rafic Hariri, Beyrouth, Lebanon 2 Faculty of Agricultural Engineering and Veterinary Medicine, Lebanese University, Dekwaneh, Lebanon Received 11 October 2013; accepted 03 January 2014 Abstract: Activated carbon derived from pine cones waste was prepared by carbonization at 450 ◦ C, activated by different activating agents: ZnCl 2 , H 2 SO 4 and NaOH, and then pyrolyzed at 600 ◦ C. Adsorption of Cr VI and other heavy metals (Mn II, Fe II, Cu II) on activated carbons was investigated to evaluate the adsorption properties. Special attention was paid to the effects of carbon surface functionalities that were analyzed by FT-IR and zeta potential study. Moreover, XRD study of activated carbon was also carried out. Results had shown that activated carbon by NaOH was the best adsorbent for removal of chromium VI from wastewater. The solid-solution interaction was determined by analyzing the adsorption isotherms at room temperature at different pH. When pH is above 4, the removal fraction of Cr (VI) ions decreased with the increase of pH. The removal fraction of Cr (VI) ions decreased below pH 4. The preferable removal of Cu (II) over Mn(II) and Fe (II) could be due to its lower affinity to solvent.Pseudo-second order equation provided the better correlation for the adsorption kinetics data. Equilibrium isotherms were determined by Fowler-Guggenheim model. Keywords: Activated carbon • Chemical treatment • Surface properties • wastewater treatment • heavy metals © Versita sp. z o.o. 1. Introduction Heavy metal pollution is a global issue, although severity and levels of pollution differs from place to place. At least 20 metals are classified as toxic with half of them emitted into environment in concentrations that cause great risks to human health. Severe effects include reduced growth and development, cancer, organ damage, nervous system ∗ E-mail: bachar.kobaissy@ul.edu.lb damage, and in extreme cases death [1]. This is mainly due to their persistency and tendency for bioaccumula- tion in several of the components of the ecosystem [2]. To prevent heavy metal pollution, it is important to apply effective purification processes of wastewaters. Conven- tional methods like precipitation are unfavorable espe- cially when dealing with large volumes of matter which contains heavy metal ions in low concentration. Typically these ions are precipitated as hydrated metal oxides or hydroxides. Precipitation is accompanied by flocculation or coagulation, and one major problem is the formation of large amounts of sediments containing heavy metal ions 90