An investigation into the equilibrium, isotherm,and thermodynamic characteristics of Mn(II) ion biosorption using pine cones

It is now evident that the utilization of agricultural waste materials represents one of the most effective approaches for the remediation of heavy metal-contaminated water. In this study, Kosovo pine cones were used as a natural, low-cost biosorbent to remove Mn(II) ions from aqueous solutions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the biosorbent before and after Mn(II) treatment. The observed peak shifts after Mn(II) biosorption suggest interactions between manganese ions and functional groups, particularly hydroxyl and amino groups, rather than carboxyl and carbonyl groups. The main parameters affecting the biosorption process, such as pH, biosorbent dose, initial solvent concentration, contact time, and temperature, were investigated to determine optimal conditions. The efficiency of manganese biosorption was strongly influenced by the pH of the aqueous solution, with optimal removal typically observed at a neutral pH of approximately 7. Isotherm parameters corresponding to the Langmuir and the Freundlich models were derived from the experimental data. The Langmuir isotherm model (R2 0.997) provided the best fit to the equilibrium data, with a maximum biosorption capacity of 36.90 mg/g at 288 K. Thermodynamic parameters (ΔHo, ΔSo, and ΔGo) were determined, indicating that the biosorption process is exothermic, favorable, and spontaneous. The study confirms that pine cones are an efficient biomaterial for the treatment of Mn(II)-contaminated water