Abstract—Due to the increasing global demand over the last few decades, low-cost and eco-friendly adsorbents have been intensively sought as alternatives to traditional ones. This study examines the possibility of using raw hazelnut and walnut shells for the removal of Reactive Blue 49 from aqueous solutions. Operational parameters, including initial pH, initial dye concentration, adsorbent dosage, and contact time, were examined in batch adsorption experiments. The surface morphology and textural properties of the shells were characterized using scanning electron microscopy and Brunauer-Emmett-Teller (BET) surface area analysis. The experimental results showed that dye removal was strongly influenced by solution pH, with the highest removal efficiencies observed under acidic conditions (pH 2). At low initial dye concentrations (5–10 mg/L), removal efficiencies between approximately 80% and 97% were obtained. The maximum experimental adsorption capacities reached 1.81 mg/g for hazelnut shells and 2.35 mg/g for walnut shells at an initial dye concentration of 40 mg/L. Hazelnut shells generally exhibited higher removal efficiency than walnut shells under most experimental conditions. Although walnut shells exhibited a higher maximum adsorption capacity, hazelnut shells demonstrated superior removal efficiency under most experimental conditions. Equilibrium data were analyzed using Freundlich, Temkin, and Hill isotherm models, while the adsorption kinetics were evaluated using the pseudo-second-order model and a reversible adsorption–desorption model with an oscillatory correction term. The results indicate that dye adsorption on both lignocellulosic materials is primarily governed by surface heterogeneity and interactions occurring at the adsorbent surface. These results demonstrate that the studied hazelnut and walnut shells can serve as promising, sustainable alternatives to conventional adsorbents for the treatment of dye-contaminated wastewater.
Keywords—non-conventional adsorbents, hazelnut shell, walnut shell, reactive dye, adsorption, equilibrium isotherms, adsorption kinetics
Cite: Keti R. Ivanova and Silviya I. Lavrova *, "Characterization and Adsorption Performance of Walnut and Hazelnut Shells for the Removal of Reactive Blue 49 Dye from Water," International Journal of Environmental Science and Development vol. 17, no. 5, pp. 454-463, 2026.
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