Thermodynamic and kinetic studies of Eriochrome black adsorption on activated charcoal prepared from lemon leaves

The research included the preparation of activated carbon with nanoscale from the fallen leaves of lemon trees. The activated carbon was characterized using the following techniques: FT-IR, XRD, AFM, EDX and SEM. The results showed that the activated charcoal does not contain any active group, (i.e. chemically inert), has nanoscale particle and excellent porosity. Some of its physical properties, such as humidity (8%), ash (0.1 g), density (0.4 g cm(-3)) and pH(7.2) were studied. The results of the adsorption process showed that the appropriate concentration of the Eriochrom black was 30 mg l(-1) and the appropriate weight of the new activated carbon was 0.07 g under equilibrium time of 25 min. The adsorption process is subjected to the psedusecond-order equation according to the R2 correlation coefficient of 0.9999. The thermodynamic functions of the adsorption process were calculated at different temperatures (10 degrees C-50 degrees C), where the adsorption process was found to be an exothermic process (Delta H = -) thusly, the adsorption is physically occurred because it is less than 40 KJ/mole and the free energy is negative (G = -). These thermodynamic results mean that the adsorption process occurs spontaneously with negative entropy value (Delta S = -). Moreover, adsorption isotherms were calculated and the results showed that Freundlich and Langmuir were suitable to represent the adsorption process of the dye.