Adsorption of Aniline Derivatives on Modified Activated Carbon

Among the physicochemical and biological methods of water purification from organic and inorganic contaminants, adsorption is the most suitable and advanced technique due to the high removal efficiency, easy operation, economic availability, and reusability of adsorbents. The removal of organic contaminants from water sources can be improved by using appropriate target adsorbents. Currently, much attention is paid to the production of carbon-containing sorbents from biorenewable raw materials (agro-industrial residues, wood processing products, wastes from various industries). The structural and sorption properties of fruitstone activated carbon from apricot kernels (FAC) and its modified sample obtained by impregnation with iron salts (Fe-FAC) have been studied. It has been shown that FAC modification leads to an increase in the total specific surface area, the surface of meso- and micropores, and the volume of pores. An increase in the static cation- and anion-exchange capacities was observed. The adsorption of p-chloroaniline, p-nitroaniline, and m-nitroaniline was studied under steady-state conditions at temperatures of 5, 20, and 40°C. In all the cases, adsorption is better on the modified adsorbent. The obtained results were described by the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. Thermal studies allowed us to calculate thermodynamic parameters, such as the Gibbs free energy change and process enthalpy and entropy. It has been revealed that the adsorption of the studied compounds occurs as a spontaneous exothermal process.