Removal of Brilliant Green Dye from Aqueous Solutions Using Home Made Activated Carbons

Abstract

Activated carbon materials were prepared from the Brazilian pine-fruit shell (Araucaria angustifolia) by chemically activated carbon (CAC) and chemically and physically activated carbon (CPAC), and tested as adsorbents for the removal of brilliant green (BG) dye from aqueous effluents. The mixed activation process leads to increases in the specific surface area, average porous volume, and average porous diameter of the adsorbent CPAC when compared to CAC. The effects of shaking time, adsorbent dosage and pH on the adsorption capacity were studied. BG uptake was favorable at pH values ranging from 2.0 to 10.0 for both CAC and CPAC. The contact time required to obtain the equilibrium using CAC and CPAC as adsorbents was 4 h at 298 K, respectively. The fractionary-order kinetic model provided the best fit to experimental data compared with other models. Equilibrium data were better fit to the Sips and Redlich-Peterson isotherm models using CAC and CPAC as adsorbents. The enthalpy and entropy of adsorption of BG were obtained from adsorption experiments ranging from 298 to 323 K. IntroductionDyes are a kind of organic compound with a complex aromatic molecular structure that can bring bright and firm color to other substances. However, the complex aromatic molecular structures of dyes make them more stable and more difficult to biodegrade [1,2]. The extensive use of dyes in different kinds of industries often poses pollution problems in the form of colored wastewater discharged into environmental water bodies [3].The most efficient method for the removal of synthetic dyes from aqueous effluents is the adsorption procedure [4][5][6]. This process transfers the dye species from the water effluent to a solid phase thereby keeping the effluent volume to a minimum [7][8][9]. Subsequently, the adsorbent can be regenerated or stored in a dry place without direct contact with the environment [5][6][7][8][9].Activated carbon is the most employed adsorbent for toxic species removal from aqueous effluents because of well-developed pore structures and a high internal surface area that leads to its excellent adsorption properties [10,11]. Besides these physical characteristics, the adsorption capacity is also dependent on the source of organic material employed for the production of the activated carbon [10][11][12][13], as well as the experimental conditions employed in the activation processes [11].Activated carbon can be prepared using a variety of chemical [14] and physical [15] activation methods and in some cases using a combination of both types of methods [16]. Chemical activation is the process where the carbon precursor material is firstly treated with aqueous solutions of dehydrating agents such as H 3 PO 4 , ZnCl 2 , H 2 SO 4 , and KOH. Afterward, the carbon material is dried at 373-393 K to eliminate the water. In a subsequent step, the chemically treated carbon material is heated between 673 and 1073 K under nitrogen atmosphere [11,17]. The physical activation consists of a thermal treatment of previously carbonize...

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