Effect of pH on the adsorption of Sunset Yellow FCF food dye into a layered double hydroxide (CaAl-LDH-NO3)

Effluents that are discarded by food industries are important sources of water pollution because they can contain large concentrations of organic matter and have intense color. The “batch” method for evaluating the adsorption of Sunset Yellow FCF food dye into a CaAl-LDH-NO3 layered double hydroxide (LDH) system was investigated. The CaAl-LDH-NO3 was coprecipitated at variable pH and characterized by X-ray diffraction, infrared spectroscopy and scan electron microscopy. Adsorption experiments were carried out as a function of pH, contact time and dye concentration. The results showed that pH affects the adsorbent surface charge and the degree of anionic dye dissociation. The effective pH range for dye removal was between 4.0 and 10. Lower pH potentially causes dissolution of CaAl-LDH-NO3. The Langmuir equation adequately describes the equilibrium data. The best-fits showed a maximum adsorption of 398.41 mg/g or 0.88 mmol/g.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights• pH affects the adsorbent surface charge and the degree of anionic dye dissociation. • CaAl-LDH-NO3 is an effective adsorbent for the removal of Sunset Yellow FCF food dye from aqueous solutions. • Lower pH potentially causes dissolution of the CaAl-LDH-NO3.