Removal of reactive red 120 in aqueous solution using mg-hydrotalcites as adsorbents solids: Kinetics and isotherms

Abstract

Reactive red 120 (RR120) is a widely used dye in the textile industry but its release in aqueous wastewater is a serious problem due to its toxicity and low biodegradability. The aim of this work was to evaluate the effect of the trivalent cation of magnesium-based materials type hydrotalcite as adsorbents applied to RR120 dye removal in aqueous solution. The samples were synthesized by continuous coprecipitation and were characterized by surface area measurements, X-ray diffraction and temperature-programmed desorption of CO2. Dye adsorption tests were carried out using different adsorbent dosages and contact time. The kinetic adsorption was studied for the pseudo-first and pseudo-second order models. The equilibrium adsorption data were fitted to the Langmuir, Freundlich and Redlich-Peterson isotherm models. The most suitable adsorption conditions were found at a residence time of 60 min and solid dosage of 2.5 g/L for HDL-MgFe, 2 g/L for HDL-MgAl and HC-Mg. The results showed that pseudo-second order model, as well as the Langmuir and Redlich-Peterson models best described the removal process. The Al containing compound presented the best results due to a better interaction between strength and number of basic sites.