_________________________________________________________________________________________________________________________________ Full Paper A STUDY ON THE OPTIMIZATION AND ADSORPTION CAPACITY OF ACTIVATED CARBON PRODUCED FROM POLYVINYL CHLORIDE (PVC) WASTES O.D. Alabi-Babalola Department of Chemical Engineering, Obafemi Awolowo University, Ile-Ife, Osun-State, Nigeria. E.F. Aransiola Department of Chemical Engineering, Obafemi Awolowo University, Ile-Ife, Osun-State, Nigeria. aransiolaef@gmail.com T.D. Shittu Department of Chemical Engineering, Obafemi Awolowo University, Ile-Ife, Osun-State, Nigeria. ABSTRACT Activated carbon (AC) was prepared by the pyrolysis of polyvinyl chloride (PVC) wastes. This was with a view to optimize and study its adsorption capacity through various activation processes. The optimization study was carried out using the central composite design of the response surface methodology (RSM). The effects of the reaction conditions: carbonization temperature (400 – 500 oC), concentration of chemical activating agents (0.50 – 2.00 M H2SO4 and KOH) and activation time (45 – 60 min) on the yield and other physicochemical properties were investigated. The study revealed that an optimum yield of 80 % was achieved at an average activation time of 48-50 min, and average temperature of 425-450 oC. Maximum adsorption capacity was obtained at optimized reaction conditions of 0.50 M, and 500 oC. However, the optimum time for both PVC-H2SO4 and PVC-KOH are 46.46 and 55.35 min respectively. Fourier transform infrared (FT-IR) analysis revealed the presence of oxygen-surface complexes such as the carbonyls and O-H groups on the surface of the AC which was due to chemical activation. Scanning electron microscope (SEM) analysis shows the presence of pores and cave-type openings on the carbon surface sites, thus, confirming the porosity in the carbons. The adsorption data was found to perfectly fit the Freundlich model at an adsorbent dosage of 0.75 g/100 mL of adsorbate. Equilibrium was reached between 60 and 75 min. The kinetic studies showed that the pseudo-second-order model provides the best correlation for the dynamic behaviour for the sorption of inorganic ions onto AC with a kinetic rate constant of 0.0178 min-1 and correlation coefficient of 0.9988. Keywords: Activated carbon, Pyrolysis, Chemical Activation, Polyvinyl chloride, Optimization and Adsorption. 1. INTRODUCTION Activated carbons (AC) are carbon-based materials that are synthesized via the oxidation of the carbon atoms that are found on both the inner and outer surfaces. They are usually prepared by the pyrolysis of materials containing a high percentage of carbon and low content of inorganic substances. This is followed by activation either by physical or chemical means. The activation of the carbonized products helps to oxidize the pores of the carbon and further develop their internal pore structures. Activated carbon are often characterized by large surface areas, highly-developed porosity, and tunable functional groups (Bansode et al., 2003, Zongxuam et al., 2003). The choice of precursors for the preparation of activated carbon depends on factors such as cost, availability and renewability of the material, amount of nutrient, and organic content of the material. In a bid to reduce the production cost, effort has been made by researchers all over the world towards utilizing renewable and relatively cheaper precursors. Such precursors include wood, agricultural byproducts (Wang et al., 2007), coal, synthetic resins, forest and industrial wastes (Cunliffe and Williams,1999, Lua and Yang, 2005, Ademiluyi et al., 2009). However, previous studies have mainly focused on the preparation of the activated carbon from agricultural byproducts and forest wastes as an alternative for the commercial activated carbon (Buasri et al., 2013). Examples of such byproducts/wastes are plywood and chipboard wastes, grain sorghum (Diao et al., 2002), molasses (Legrouri et al., 2005), coconut shells (Radhika and Palanivelu, 2006), waste apricot (Basar, 2006), rubber wood sawdust (Prakash Kumar et al., 2006), oil palm fiber (Tan et al., 2007),, sugar beet bagasse (Onal et al., 2007), bamboo, rattan sawdust (Hameed et al., 2007). The process of producing activated carbon involves two steps (Baker et al., 1992). The first step involves the carbonization of raw carbonaceous materials in an inert atmosphere. In this case, the carbon-containing materials are pyrolysed under inert conditions at temperatures ranging from 600 - 900 °C. The second step involves the activation of the carbon product. The carbonized material undergoes further treatment in order to enhance the porosity and adsorption performance for commercial application (Girgis et al., 2002). Activation could either be by chemical or physical means (Marsh and Rodríguez-Reinoso, 2006a; Inamullah et al., 2008). Physical activation involves conversion of the precursor or carbonized carbon into activated carbons using gases or oxidizing atmospheres, and the activation temperature range of 600–1200 °C (Inamullah et al., 2008). Chemical activation involves the impregnation of the precursor raw material with some chemicals prior to carbonization, which may be typically an acid, a strong 34 Ife Journal of Technology, Vol. 26(1), 34 – 46, 2019 1115-9782 © 2019 Ife Journal of Technology http://www.ijtonline.org