Mechanism of interaction of hydrocalumites (Ca/Al-LDH) with methyl orange and acidic scarlet GR

The development of new materials for water purification is of universal importance. Among these types of materials are layered double hydroxides (LDHs). Non-ionic materials pose a significant problem as pollutants. The interaction of methyl orange (MO) and acidic scarlet GR (GR) adsorption on hydrocalumite (Ca/Al-LDH-Cl) was studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), scanning electron microscope (SEM), and near-infrared spectroscopy (NIR). The XRD results revealed that the basal spacing of Ca/Al-LDH-MO was expanded to 2.45 nm, and the MO molecules were intercalated with a interpenetrating bilayer model in the gallery of LDH, with 49° tilting angle. Yet, Ca/Al-LDH-GR was kept the same d-value as Ca/Al-LDH-Cl. The NIR spectrum for Ca/Al-LDH-MO showed a prominent band around 5994 cm−1, assigned to the combination result of the NH stretching vibrations, which was considered as a mark to assess MO− ion intercalation into Ca/Al-LDH-Cl interlayers. From SEM images, the particle morphology of Ca/Al-LDH-MO mainly changed to irregular platelets, with a “honey-comb” like structure. Yet, the Ca/Al-LDH-GR maintained regular hexagon platelets, which was similar to that of Ca/Al-LDH-Cl. All results indicated that MO− ion was intercalated into Ca/Al-LDH-Cl interlayers, and acidic scarlet GR was only adsorbed upon Ca/Al-LDH-Cl surfaces.

Graphical abstractMethyl orange and acidic scarlet GR have different routes reacted with Ca/Al-LDH-Cl. Methyl orange is through intercalation into Ca/Al-LDH-Cl, while acidic scarlet GR is only adsorbed on with Ca/Al-LDH-Cl.Figure optionsDownload full-size imageDownload high-quality image (99 K)Download as PowerPoint slideHighlights► Hydrocalumites (Ca/Al-LDH) were synthesized and characterized. ► Methyl orange and acidic scarlet GR modified the Ca/Al-LDH-Cl. ► This work has shown that methyl orange was intercalated with Ca/Al-LDH-Cl. ► Acidic scarlet GR was adsorbed onto Ca/Al-LDH-Cl surfaces.