The application of activated carbon produced from used newspaper in the removal of methylene blue dye from aqueous solution: isotherm, kinetic and thermodynamic study

Activated carbon is widely used at various industrial processes such as water and wastewater industries. Activated Carbon (AC) is an adsorbent which is mostly employed for removing dye from aqueous solutions because of its excellent adsorption properties. Therefore, AC is used in the adsorption process in order to remove different pollutants from the wastewater, especially colored contaminants. however; the use of commercial grade of activated carbon is faced with difficulties due to the high price of raw materials. The used newspaper found as a main component of solid wastes can be used for producing of activated carbon. One of the most important industrial pollutants, especially in textile industries, is the dyes that even at low concentrations of one parts per million (ppm) are recognizable by naked eyes. One of the mostly consumed materials in the dye industry is Methylene Blue (MB) which is used for cotton and silk dyeing. Up to now, a great number of methods have been proposed in order to remove dyes from the industrial waste water, among which adsorption is the most acceptable due to its cost effectiveness and the possibility of usage in large scales. The aim of this study is to evaluate the performance of activated carbon produced from the used newspaper for the removal of methylene blue dye in aqueous solution. KOH solution (weighted ratio of 1:3) was used to activation. The carbonization process was applied at 500˚C with the rate of 17˚C/min. After carbonization, the sample was cooled down to room temperature and then washed with distilled water until the pH of the filtered water was stabilized at 7.5. N2 adsorption at 77K is used to characterize the produced activated carbon using BET isotherm. To evaluate the performance of methylene blue dye removal, the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms with pseudo-first and pseudo-second order and inter-particle diffusion kinetic models were used. Thermodynamic parameters such as enthalpy (ΔΗ˚), entropy (ΔS˚) Gibbs free energy (ΔG˚) were also calculated. Based on the results, the values of SBET and VTOTAL were obtained 66.01 m2/g and 0.063 ml/g, respectively. According to the R2 and sum of squares for error (SSE%) values and regression curves, the optimum isotherm and kinetic model were determined Freundlich and pseudo-second order ones, respectively. In addition, qmax constant was obtained 68.03 mg/g for Langmuir isotherm. Kinetic parameters showed the adsorption of methylene blue dye on the activated carbon is endothermic and spontaneous. Also, (ΔG˚) in physical adsorption was changed from 0 to -20 kJ/mol, while the amount of the chemical adsorption will changed between -80 to -400. Finally, the activated carbon obtained from used newspaper in this study showed a better specific surface area and adsorption capacity for methylene blue dye adsorption in compared with other grades. Thus, the production of activated carbon from used newspaper should be considered as a cheaper and more effective alternative.