Estudo da adsorção do corante amarelo de tartrazina em hidróxido duplo lamelar contendo níquel e alumínio

Abstract

The inadequate dumping of effluents into rivers and seas by industries from different segments has caused great environmental impact and directly influenced different aquatic ecosystems. To remove these effluents, the most commonly used process is adsorption, which consists of retaining particles on the surface of solids. In this sense, this work proposed the kinetic study and other adsorption parameters of tatrazine yellow dye in aqueous solution. For this purpose, lamellar double hydroxides (LDH) containing Ni and Al in ratios 1; 0.5 and 0.25, named as HDL-Ni0,5Al0,5, HDL-Ni0,33Al0,67 e HDL-Ni0,2Al0,8 espectively, intercalated with the terephthalate anion, which were prepared via coprecipitation at pH controlled. HDL is a hydrotalcite-type compound with the general formula [M2+(1-x) M3+X (OH)-2]x+ A-x/n m.H2O .XRD results confirmed the formation of HDLs through (003) and (110) reflections, and the FTIR spectra showed characteristic hydroxyl bands between 3200-3600 cm-1, as well as absorption at 1600cm-1, and 800- 860 cm-1 related to the terephthalate anion. Furthermore, the Point of zero charge (PZC) was determined using the 11-point method, obtaining values of 5.51, 5.31 and 6.67 for HDL-Ni0,5Al0,5, HDL-Ni0,33Al0,67 e HDL-Ni0,2Al0,8. In analyzing the influence of the initial pH, the three HDLs produced demonstrated greater efficiency at an acidic pH equal to 2. Adsorption tests involving contact time demonstrated that HDLNi0,5Al0,5 and HDL-Ni0,33Al0,67 reached maximum dye removal, reaching values above 90% in solutions of 40 and 80 mg/L of contaminant, and above 30% for 160mg/L. with contact time starting at 120 minutes for concentrations of 40,80 and 160 mg/L. While HDL-Ni0,2Al0,8 the contact time was from 240 minutes, obtaining removal above 50% for the respective concentrations. Evaluating the influence of temperature, it was observed that increasing the temperature from ~29oC to 50oC promoted an increase in the removal of the dye in the solution, with all adsorbents being indicative of an endothermic process. Finally, in the kinetic study, the model that best fit the experimental data was the pseudo-second order model, indicating that the process of adsorption of the tartrazine yellow dye in an aqueous is controlled by chemisorption.