Effect of alginate on the removal of yellow 6 by a biopolymer-ferric zeolite composite

Organic compounds such as azo dyes have been detected in wastewater due to their wide use in different industries. Azo dyes, i.e. yellow 6, cannot be eliminated by conventional methods of wastewater treatments, the dyes cause aesthetic problems and also affect aquatic biota by reducing processes such as photosynthesis and the development of bacteria that participate in the degradation of water impurities, by reducing the penetration of sunlight into water bodies. In this work the adsorption properties of clinoptilolite-type zeolite, modified with FeCl3, HCl and alginate-zeolite composites were evaluated for the removal of yellow 6 dye from aqueous solutions. The materials were characterized by means of infrared spectroscopy (FTIR), X-ray diffraction (XRD), specific surface area by the Brunauer-Emmet-Teller method (BET) and scanning electronic microscopy (SEM). ZFe and PAlg/ZFe composite showed the best adsorption properties for yellow 6, the materials ZNat, PAlg, PAlg/ZNat showed little removal of dye from the aqueous solutions. Iron-modified zeolite (ZFe) showed the highest removal capacity (0.468 ± 0.003 mg/g) with a percentage of 92%. The kinetic data were best adjusted to the Ho-McKay model indicating chemisorption phenomenon. The isotherms were best fitted to the Langmuir model indicating that the adsorption of the dye was carried out by means of a monolayer process on a homogeneous surface. Iron was released from the ZFe during the adsorption process but not from PAlg/ZFe composite. In general, the composite showed the best conditions for the removal of yellow 6 from aqueous solutions.