Adsorption of phenylalanine on layered double hydroxides: effect of temperature and ionic strength

• Published in: Journal of materials science 2008, Vol.43 (2), p.434-439
• Main Authors: Silvério, Fabiano, dos Reis, Márcio José, Tronto, Jairo, Valim, João Barros
• Format: Article
• Language: English
• Subjects: adsorbents; Adsorption; Aluminum; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Electrokinetics; Exact sciences and technology; Fourier transform infrared spectroscopy; General and physical chemistry; Hydrophobicity; Hydroxides; ionic strength; Ions; Isotherms; Magnesium; Materials Science; Phenylalanine; Polymer Sciences; sodium chloride; Solid Mechanics; Solid-liquid interface; sorption isotherms; Strength; Surface chemistry; Surface physical chemistry; temperature; Temperature effects; Waste water; Wastewater; zeta potential
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-007-2202-9

In this work we report the adsorption of phenylalanine (Phe) on Magnesium Aluminum Layered Double Hydroxides (Mg–Al–CO₃-LDH) at two different temperatures (298 and 310 K) and under two distinct ionic strength conditions (with and without the addition 0.1 M of NaCl). The adsorption isotherms exhibit the same profile in all conditions, and they only differ in the amount of removed Phe. At lower ionic strength, the isotherms are almost identical at both temperatures, except for the last points, where the increase in temperature causes a decrease in the amount of adsorbed Phe. An increase in ionic strength results in a decrease in Phe adsorption. The electrokinetic potential decreases as the amount of adsorbed Phe increases, and only positive values are observed. This indicates that the surface of the adsorbent is not totally neutralized and suggests that more Phe could be removed by adsorption. The presence of Phe on the solid is confirmed by FTIR spectra, which present the specific bands assigned to Phe. The hydrophobicity of the amino acid probably contributes to its extraction, thus enabling the removal of a great amount of Phe. In conclusion, LDH is potentially applicable in the removal of Phe from wastewater.