Application of Waste Basil Seed for Removal of Methylene Blue from Aqueous Solutions

In this study, waste basil seed (BS) was prepared and evaluated for the removal of methylene blue (MB) dye from aqueous media. BS was characterized using scanning electron microscopy, specific surface area, surface functional groups, and the point of zero charge (pH_pzc). Spherical particles were observed in virgin BS. The specific surface area and pH_pzc value were 0.265 m²/g and 5.59, respectively. In addition, acidic and basic surface functional groups were measured as 0.050 and 0.605 mmol/g, respectively. The MB adsorption study demonstrated that the adsorption capacity increased with increasing initial concentration (10-100 mg/L) and with decreasing temperature (45 -7°C). The pH of the MB solution significantly affected adsorption, with the highest uptake observed at the neutral and basic pH levels. The data fitted well to the Langmuir isotherm model and the pseudo-2nd-order model, with correlation coefficients of 0.899-0.993 and 0.996, respectively, under the tested conditions. Furthermore, elemental distribution analysis, binding energy evaluation, and adsorption capability revealed that MB adsorption on the BS surface was closely related to the cellulosic hydrocolloid components. Overall, BS exhibited a promising adsorption capacity and could serve as an effective material for MB removal from aqueous media.