Comparison of Adsorption Behaviour of Activated Carbons From Low-Rank Coals for Rhodamine B

In this study, six activated carbons were synthesised using low-rank coal from Labin and Spitsbergen through single- and two-step KOH activation methods. The materials were evaluated for their ability to adsorb rhodamine B from aqueous solutions. The method of activation and impregnation ratio significantly affected the structural and sorption properties of the carbons. BET surface areas ranged from 602 to 855 m²/g. Surface functional groups varied depending on the precursor used. Adsorption experiments explored the effects of initial dye concentration, contact time, adsorbent mass, shaking speed and pH. Kinetic and isotherm models were applied to understand the adsorption mechanism. The linear Langmuir isotherm best fit the data, indicating uniform adsorption sites, while the process followed a pseudo-second-order kinetic model. Maximum adsorption capacities ranged from 100 to 294 mg/g. One adsorbent demonstrated excellent reusability, achieving up to 90% desorption efficiency after three cycles. These results highlight the material's strong potential for removing organic pollutants from water.