Abstract

Red Ponceau (RP) is a dye used in various applications such as food coloring agent. In recent years it has been removed from the list of food dyes because it is suspected to be toxic and carcinogenic [1]. In this work, two alumina adsorbents, one chemically synthesized [2] and the second modified by phosphate ions (modified alumina), were used for the removal of RP from an aqueous solution. The effects of various parameters such as pH, adsorbent concentration, contact time and temperature on adsorption capacity were studied. The results show that the removal of RP is very fast and equilibrium is reached after 17 minutes. The adsorption kinetics follows a pseudo-second order model with a correlation coefficient R² = 0.99 and the theoretical adsorption capacity is very close to experimental results. The adsorption isotherm gives an experimental maximum adsorption capacity of 0.0539 mmol/g (40.99 mg/g) of RP on the phosphate modified alumina. The adsorption isotherm shows that the Sips model is more suitable for input than Langmuir model and Freundlich model with a correlation coefficient R² = 0.99 and a maximum adsorption capacity of 0.0635 mmol/g (45.65 mg/g). The study of the effect of temperature shows that adsorption increases weakly with this setting. The regeneration of the modified alumina has been successfully performed by calcination at 600C. The results show that the regenerated modified alumina is more efficient than the original alumina to remove RP with an adsorption capacity in equilibrium at initial concentration of 0.09 mM passed for 0.0216 mmol/g on alumina to 0.0224 mmol/g on modified alumina.

Key words: Adsorption; Desorption; Alumina; Modified alumina; Ponceau S

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