Synthesis and characterization of ZnO/activated carbon nanocomposite for the removal of cationic dye from aqueous solutions

In this work, we focused on the modification and characterization of activated carbon supported by ZnO nanoparticles. Our study was based on the modification process involving the synthesis of two types of modified activated carbon using metallic nanoparticles, each following different protocols. Secondly, we concentrated on characterization methods such as the methylene blue index, the iodine value, the determination of the point of zero charge, infrared analysis, and the application of adsorption for methylene blue. The adsorbent with the highest iodine number has the largest specific surface area; in this case, it is the ZnO-AC from protocol 2, with an iodine number of 1145.11 mg.g-1 for activated carbon modified with ZnO nanoparticles. The total amount of surface acidic groups of the modified activated carbon increased after modification, contrary to the commercial activated carbon. These results are confirmed by pHzpc and FT-IR analyses of the activated carbon studied. The pHzpc for all the activated carbons studied is lower than the pH of the aqueous solution, indicating they have more acidic surfaces. The adsorption results of methylene blue showed that the activated carbon modified in protocol two was the more efficient one but couldn’t exceed the commercial efficiency. The non-linear regression analysis method showed that the methylnene blue adsorption data followed Temkin's isothermal model rather than that of Langmuir and Freundlich.. The adsorption capacities for nanocomposite from protocol 1 and the Merck activated carbon are 610.23 mg.g-1 and 553.03 mg.g-1, respectively. These values indicate that our activated carbon produced in the laboratory has a strong adsorption of methylene blue on Merck and modified activated carbon is probably due to increased porosity. The study confirms that activated carbon doped with ZnO nanoparticles can be useful for eliminating methylene blue in aqueous solution.