Optimizing textile dye removal by activated carbon prepared from olive stones

Abstract

Activated carbon prepared from black and green olive stones were successfully used as an adsorbing agent to remove methylene blue from water. Scanning electron microscopy showed how the deep abundant cavities were occupied after adsorption. Fourier- transform infrared spectroscopy showed various functional groups on both adsorbents before and after adsorption. It was also noted that the highest N%, H% and C% prior to adsorption was found in black activated carbon olive stones. Furthermore, results showed that the maximum adsorption of methylene blue was at the optimum pH value of 10. The maximum adsorption capacity of methylene blue was 714 and 769 mg/g for black and green activated carbon olive stones, respectively. Methylene blue removal efficiency reached its maximum capacity at approximately 79%. The equilibrium data were best fitted by Freundlich isotherm reaching R2 value of 98%. In addition, thermodynamic studies resulted in negative ∆G◦ value indicating that the adsorption process was spontaneous and feasible, negative ∆H◦ value confirming the exothermic reaction of the adsorption process, and positive ∆S◦ value for green activated carbon olive stones was higher than that for black activated carbon olive stones indicating the good affinity of methylene blue towards the adsorbent.