Almarei milk is produced in Saudi Arabia from aqueous solutions; this study investigates its adsorption behavior pertaining to three types of anthocyanin pigments that are used as natural food colorants and adsorbents. The three anthocyanin pigments were extracted from red cabbage (RC), grape peel (GP), and pomegranate peel (PP). The initial dye concentrations were 10–50 mg/L and temperature of the solution was 35 °C. For an equilibrium isotherms and kinetic data were evaluated using the adsorption isotherms models such as Freundlich and Langmuir models. The results which were recorded show that the best adsorption model fit with the experimental data was Langmuir model in contrast with the Freundlich model. Also more suitable adsorption kinetics model was pseudo-second order and intraparticle diffusion models than the first-order reactions. An exothermic nature was found form the results of thermodynamic adsorption for each of thermodynamic parameters like entropy (S◦), (H◦) enthalpy, and free energy (G◦).

Fatima A. Al-Qadri, Raiedhah Alsaiari, Mabkhoot Alsaiari, Iman Mohammad Shedaiwa, Mervate Mohamed Mohamed and Esraa Mohamed Musa