Synthesis of activated carbon from the waste of raisin production companies and evaluation of its use in the removal of methylene blue in comparison with commercial sorbents

Raisin factories face a problem called waste and unusable waste in their industry. Due to the richness of industrial waste in this industry from carbon, in this work, we synthesized activated carbon by chemical method from raisin waste. For the synthesis of activated carbon, a chemical method with a zinc chloride activating agent was used in one to one mass ratio. After the optimization of various parameters such as type of activation agent, the ratio of activating agent, carbonization temperature and carbonization time, the best conditions for activated carbon were obtained. Then, in order to evaluate the efficiency of the synthesized activated carbon, a methylene blue dye removal test as a model was performed. Optimal conditions for the removal of methylene blue dye using the activated carbon including neutral pH, ambient temperature and the amount of adsorbent 0.01 g in 10 mL of solution with a concentration of 20 mg L-1 were obtained. In these conditions, the removal efficiency is more than 99%. The adsorption capacity is about 20 mg g-1 and the reaction kinetics is quasi-second order and according to thermodynamic studies the endothermic reaction is spontaneous and with increasing entropy. The dye adsorption mechanism on the adsorbent also follows the Langmuir isotherm, which indicates the uniformity of the adsorbent surface and the monolayer adsorption. Finally, in order to compare the performance of synthetic activated carbon, the amount of dye removal under optimal conditions was compared with the commercial activated carbon including Merck, Jacobi and activated carbon obtained from the almond shell. The results showed that synthetic activated carbon can compete with commercial samples.