Modificação e caracterização de argila esmectita Brasgel visando seu uso no processo de remoção de metais pesados (Cd, Ni e Cd/Ni).

Abstract

The adsorption process can be effectively used in removing heavy metals from wastewater. The use of low cost materials as adsorbents increases the competitive advantage in the process. This work was carried out in two stages, the first stage for changes were made both acid (HCI) as thermals (100, 200, 300, 400 and 500 0 C). The second step, the removal in single system (or nickel cadmium) and binary (cadmium and nickel) by Clay Brasgel natural and thermally modified at 500 °C. We used a 22 factorial design with three (3) repetitions at the midpoint analyzing the two input variables initial concentration of heavy metals (10, 30 and 50 mg.L-1), pH (3, 4 and 5). Studies were conducted equilibrium and kinetic. The data obtained (equilibrium isotherms) were applied Langmuir and Freundlich. The clay Brasgel natural and modified heat at 500 °C were characterized by various techniques. The results of the analysis of X-Ray Diffraction (XRD) and spectrophotometry Energy Dispersive X-Ray (EDX) confirmed that clay has natural Brasgel as the predominant clay mineral smectite and even mixtures of kaolinite and quartz. The thermal activation led to some modifications, such as structural modification, verified by X-ray Diffraction (XRD) and reduction in the value of the specific surface area. Based on the results of this study, it can be concluded that the acid activation partially altered Brasgel clay structure, as verified by XRD. Significant increases in specific surface areas were observed making Brasgel clay a promising adsorbent. The final results after the tests of removing heavy metals (Cd2 + or Ni2 + , Cd2 + , and Ni2 + ) showed that, generally, the clay Brasgel natural highest efficiency in removing heavy metals when compared to clay Brasgel thermally modified to 500 °C. The data obtained for natural and modified clay Brasgel thermally 500 °C were applied Langmuir and Freundlich models, and the best fit obtained for both clay Brasgel natural with the modified Langmuir model. For all systems studied, the kinetic model of adsorption pseudosecond-order were fitted to the experimental data.