A Study on the Adsorption of Rhodamine B onto Adsorbents Prepared from Low-Carbon Fossils: Kinetic, Isotherm, and Thermodynamic Analyses

The aim of this study was to obtain a series of activated carbon samples by the chemical activation of low-rank coal. The precursor was impregnated with a NaOH solution. Activated carbons were characterized by determining their textural parameters and content of surface oxygen functional groups and by using an elemental analysis. The carbons were tested as potential adsorbents for the removal of liquid pollutants represented by rhodamine B. The effectiveness of rhodamine B removal from water solutions depended on the initial concentration of the dye, the mass of rhodamine B, and the pH and temperature of the reaction. The isotherm examination followed the Langmuir isotherm model. The maximum adsorption capacity of the rhodamine B was 119 mg/g. The kinetic investigation favored the pseudo-second-order model, indicating a chemisorption mechanism. The thermodynamic assessment indicated spontaneous and endothermic adsorption, with decreased randomness at the solid–liquid interface. The experiment revealed that a 0.1 M HCl solution was the most effective regenerative agent.