Sorption of Synthetic Anionic Amaranth Dye from an Aqueous Solution on Hydrophobized Silica and Alumina

Sorption of the synthetic anionic dye Amaranth on silica chemically modified by hexadecyl groups (Diasorb-130-C16 and γ-Al₂O₃) is studied. It is found that Amaranth sorption on Diasorb-130-C16 is maximal in the acidic medium (0.5 M НСl) and totals 72%. With γ-Al₂O₃, the degree of sorption is maximal at pH 1–5 and totals 92%. Possible schemes of the dye's interaction with surfaces of the sorbent are proposed. Sorption isotherms are derived under the optimum conditions of sorption, and changes in the standard Gibbs energy are calculated. The possibility of detecting the dye on surfaces of the sorbent via diffuse reflectance spectroscopy is demonstrated.