Study of lignite as the raw material for adsorption of Pb(II) and Cd(II) ions from aqueous solution

The adsorption of two heavy metal ions, lead and cadmium, from an aqueous solution was investigated using Kosovo's lignite as the raw material. The material's properties, including nature, functional groups, surface shape, and charge, were investigated using FTIR, XRD, SEM, and pHPZC techniques. The objective of determining parameters such as initial concentration, pH, contact time, adsorbent dosage, and temperature was to understand how these variables influence adsorption. Under optimal conditions (0.125g/50cm3, 30 mg/dm3, 30 min, 200 rpm, and pH 6), Tthe removal efficiency of Pb(II) was 97.22 %, and 90.04% for Cd(II) under optimal conditions (0.125g/50cm3, 30 mg/dm3, 30 min, 200 rpm, and pH 6). To investigate the achievement of equilibrium between lignite and metal ions, two key isotherm models - s, Langmuir and Freundlich -, were applied. Based on the Langmuir isotherm model, the maximum adsorption capacities for lead and cadmium were 55.55 mg/g and 48.78 mg/g, respectively, at 288 K. The best medium for removing metal ions from lignite (desorption) is was found to be 0.5M HCl. Standard enthalpy change, standard entropy change, and Gibbs free energy indicated that the adsorption of heavy metals with onto lignite is a favorable, exothermic, and spontaneous process and is spontaneous. This investigation study shows that this lignite from Kosovo is highly effective in adsorbing lead and cadmium these two heavy metalsfrom aqueous solutions.