Modification of a silicate xerogel with cetyltrimethylammonium bromide for the adsorption of tartrazine yellow dye

Synthetic dyes present in industrial wastewater cause adverse effects on aquatic organisms and humans. Tartrazine yellow (TY) is an anionic dye used in textiles, cosmetics, and food industries, which has adverse effects on diet consumption. An alternative method for removing residues from wastewater is the adsorption process using silica xerogels. Though the use of silica materials as adsorbents of dyes has already been studied, xerogels used for this purpose have not yet completely known. The work reported here describes the study of the adsorption capacities of two silica xerogels, prepared by the sol-gel method via acid catalysis, for TY from its aqueous solutions. These two silica xerogels were synthesized using tetraethylorthosilicate as a precursor. The first was named silica xerogel unmodified (SiO2-UN), and the second was modified with a surfactant, cetyltrimethylammonium bromide (CTAB), named SiO2-CTAB. The adsorption process was realized using Ultraviolet-visible spectroscopy. The pseudo-second-order model best described the adsorption kinetics. The equilibrium data fit well to the Freundlich adsorption isotherm for SiO2-UN while for SiO2-CTAB, the results best fitted to the Langmuir isotherm model. SiO2-CTAB had a higher maximum adsorption mass value of 9,62 mg g-1 for TY than SiO2-UN, which could be attributed to electrostatic interactions. The results indicate the potential use of SiO2-CTAB as adsorbent for TY.