Preparation of Activated Carbon From Olive Stone Waste: Optimization Study on the Removal of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from Aqueous Solution Using Response Surface Methodology

Abstract

The removal efficiencies of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from aqueous solution with olive stone activated carbon (OSAC) were investigated in this paper. Central composite design method was used to optimize the preparation of OSAC by chemical activation using potassium hydroxide (KOH) as chemical agent. The optimum conditions obtained were 715°C activation temperature, 2 hours activation time, and 1.53 impregnation ratio. This resulted in removal of 99.25% Cu2+, 94.98% Cd2+, 99.08% Ni2+, 99.33% Pb2+, 99.41% Fe2+, and 99.17% Zn2+, as well as 73.94% OSAC yield. The surface characteristics of the activated carbon (AC) prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer–Emmett–Teller (BET) surface area, total pore volume, and average pore diameter of the prepared activated carbon were 886.72 m2/g, 0.507 cm3/g, and 4.22 nm, respectively. The equilibrium data of the adsorption was well fitted to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Fe2+ (57.47 mg/g), followed by Pb2+ (22.37 mg/g), Cu2+ (17.83 mg/g), Zn2+ (11.14 mg/g), Ni2+ (8.42 mg/g), and Cd2+ (7.80 mg/g). The prepared OSAC can be used for efficient removal of metals from contaminated wastewater.