Eco-Friendly Adsorption of Rhodamine B Dye Using Dragon Fruit Seeds From Foodstuffs

The study aims to remove Rhodamine B (RhB) dye from environmental samples using dragon fruit seeds (DFS) as a potential and efficient biosorbent. Several batch experiments were systematically performed over set intervals to assess how variables such as contact time, temperature, pH, adsorbent dosage, and initial dye concentration influence dye removal performance. To better understand the characteristics of DFS, its surface morphology and chemical composition were investigated using analytical tools like FTIR, EDX, and SEM. The results indicated the adsorption happened quickly within 10 minutes of contact as equilibrium was achieved. The most effective extraction of dye was achieved at pH 5. Moreover, the highest dye uptake of 0.3375 mg/g at 25°C was calculated by applying the Langmuir isotherm model. The kinetic studies showed that the adsorption conformed pseudo-second-order kinetics, with k2 = 4 × 10–4 g/mg.min and R2 = 0.998, indicating a high adsorption rate. Additionally, the process was also investigated by thermodynamic parameters, where the negative enthalpy change ΔH = –46.73 J/mol, confirms its exothermic nature, and the positive entropy change ΔS = 143.89 J/K reflects increased molecular freedom at the solid–liquid interface. At 298 K, the negative Gibbs free energy ΔG = –42.93 kJ/mol further indicates the spontaneity of the process. Based on that, the results confirmed that dragon fruit seeds provide an effective and sustainable sorbent for RhB dye removal from wastewater.