Efficient preconcentration and determination of dye molecules from aqueous solutions via solid phase extraction using malus domestica leave based bioadsorbent

The extensive use of azo dyes in industrial processes poses a significant threat to aquatic environments due to their toxicity and persistence. In this study, Malus domestica leaves were evaluated as an environmentally friendly, low-cost, and natural bio-adsorbent for the separation, preconcentration, and determination of the azo dye Drimaren Red CL-5B using a column solid-phase extraction (SPE) method. Parameters affecting the extraction efficiency, such as solution pH, initial dye concentration, sample volume, eluent type, and the interfering ions and dyes were optimized. Quantitative dye recovery (up to 98%) was achieved at pH 2. Surface charges resulted a strong electrostatic interaction between the bio-adsorbent surface and dye molecules above the pHₚzc value of 3.35. The adsorption tendency of dye on the adsorbent surface was linear in the concentration range of 5–35 ppm, while the saturation of active adsorption sites was observed after this level. Dye molecules effectively desorbed from surface by using 5 mL of 1 M HCl in ethanol. High selectivity of the method was demonstrated in the presence of common inorganic ions and co-existing dyes. Owing to its simplicity, low cost, and high extraction efficiency, the developed technique offers a promising analytical approach for the preconcentration and spectrophotometric determination of azo dyes in aquatic sample monitoring applications.