The use of biomass as a low-cost sorbent is considered an effective and eco-friendly approach for removing pollutants from water and wastewater. In this study, the adsorption behavior of nitrate was investigated using both unmodified and acid-treated Salix alba leaves, ground to a particle size of 85 mesh, as biosorbents. Nitrate, a common contaminant, poses significant health risks and contributes to eutrophication when present at high concentrations.
Adsorption kinetics and isotherm analyses were conducted at neutral pH. The acid-modified biosorbent demonstrated significantly higher nitrate adsorption compared to the unmodified form, primarily due to the introduction of a positive surface charge on the sorbent. Adsorption capacity varied under different operational conditions. The Langmuir maximum adsorption capacity (Q<sub>max</sub>) for the modified sorbent was found to be 16.806 mg/g at pH 7.
The presence of competing anions—sulfate, phosphate, and chloride—reduced nitrate adsorption efficiency, with sulfate exhibiting the highest competitive interference. Experimental data were analyzed using adsorption models, including Langmuir and Freundlich isotherms, as well as pseudo-first-order and pseudo-second-order kinetic models. Among these, the adsorption process was best described by the Freundlich isotherm and pseudo-second-order kinetics.