Adsorption of reactive dyes from aqueous solutions by layered double hydroxides

Background: Water-soluble reactive azo dyes are the most problematic dye house effluents, as they tend to pass through conventional treatment systems unaffected. The release of these compounds into the environment is undesirable and their removal becomes environmentally important. In this work, synthesis, characterization and sorption properties of hydotalcite-like compounds (Mg/Al and Mg/Fe), calcined and uncalcined, were investigated for the removal of the reactive azo dye Remazol Red 3BS. Results: The calcined compounds present higher surface area than the uncalcined. The optimum pH for sorption was found to be 6. Thermodynamic analysis reveals that the sorption is spontaneous and endothermic. Equilibrium data were fitted by a Langmuir model, and kinetic data by a second-order model. The calcined Mg/Al compound showed the highest sorption capacity, at 0.125 mmol g ^-1. Regeneration of dye loaded derivative is achieved using the surfactant SDS. Conclusions: The prepared hydotalcite-like compounds and especially calcined Mg-Al exhibited significant adsorption capacity, kinetics, and regenerative ability. Its potential applicability as sorbent should be tested in a large-scale implementation.