EXPERIMENTAL AND THEORETICAL STUDY ON STYRAX OFFICINALIS ACTIVATED CARBON ADSORPTION OF LEAD AND ZINC FROM AQUEOUS SOLUTION Tolga Depci 1,a , Ali Riza Kul 2 , Keith A. Prisbrey 1 , Yunus Onal 3 , Jan D. Miller 1 1. University of Utah, Department of Metallurgical Engineering, Salt Lake City, UT, USA 2. Yuzuncu Yil University, Department of Chemistry, Van, Turkey 3. Inonu University, Department of Chemical Engineering, Malatya, Turkey a. Corresponding author (tdepci@gmail.com) ABSTRACT: Activated carbon derived from Styrax Officinalis seeds (Balikesir, Turkey) was investigated as an alternative low-cost adsorbent for the removal of lead and zinc from aqueous solution. Activated carbon (AC) was produced chemically with a reasonable yield (38 %) and was found to have a remarkable surface area (1212 m 2 /g) with a well-developed pore structure. To determine the nature of the adsorption process, the effects of initial metal concentration (20 – 50 mg/L) was investigated using a batch adsorption technique. The adsorption isotherm data were best fitted by Langmuir model and the adsorption capacity for Pb (II) was found to be higher than adsorption capacity for Zn (II) at 298 K. Preliminary ab-initio simulations (using Gaussian 09) were also performed for both Pb and Zn adsorption. The reactivity calculations from molecular orbital theory reveal that lead has a higher reactivity towards the graphite surface in comparison to zinc. Independent Gibb’s free energy calculations (using MOPAC) further reinforce the fact that lead has a higher tendency to adsorb at the graphite surface than zinc at 298K. 1. INTRODUCTION Lead and zinc are the most utilized important heavy metals and used by many industries in large amounts. However, these heavy metals are not biodegradable and tend to accumulate in living organisms and cause several acute and chronic toxic effects on human health [Gaballah and Kilbertus, 1998; Veli and Alyuz, 2007]. A wide range of various treatment methods (namely, ion exchange, chemical precipitation, membrane system, coagulation and adsorption) have been reported to be used for removal of heavy metals [Fu and Wang, 2011]. Among the methods, adsorption has been universally accepted as one of the most effective pollutant removal processes. Adsorption for removal of Pb and Zn from industrial effluents is mostly confined to the use of granular/powdered activated carbon as adsorbent. However, commercial activated carbon is expensive and to overcome this disadvantage, considerable attention has been given to the preparation of activated carbons derived from readily available and low cost materials and waste materials, like lignite and apple pulp etc. [Depci 2012; Depci et al., 2012]. The current research focuses on finding a plausible explanation to understand the adsorption Pb and Zn by commercial activated carbon and activated carbon prepared from local biomass, as an alternative low-cost adsorbent. The emphasis of this research is to address the explanation by experimentation and with the aid of computational chemistry tools. In this regard, laboratory adsorption experiments for removal of Pb and Zn from aqueous solution were carried out using activated carbon (AC) derived from