O uso de argilas atapulgitas como dopante no desenvolvimento de diafragmas poliméricos.

Abstract

Among the electrochemical processes used in the electrolytic production of chlorine (Cl2) and caustic soda (NaOH), diaphragm technology is the most widely used in the world. For a long time, asbestos was the main material used in the manufacture of diaphragms, but its use was gradually banned due to its toxicological effect on the human body. Polymeric diaphragms have been developed to replace it. Although there are commercially available polymer diaphragms, their applications are limited because they present high market costs. In addition to polymeric materials, it is necessary to use clays and oxides in their preparation in order to reduce the permeability of the diaphragms. This work aimed to develop polymeric diaphragms and compare them with the Tephram® commercial diaphragm. Eleven diaphragms doped with three types of attapulgite clays and zirconium oxide were developed. The clays were submitted to the following characterizations: X-ray diffraction (XRD), X-ray fluorescence by dispersive energy (XRF) and particle size analysis by laser diffraction (GA). Doped polymeric diaphragms were characterized by thickness, permeability and resistivity measurements. The results showed that the Basf and Brazil Minas atapulgites had the smallest diameters and a wide distribution of the particle size, the Basf atapulgite showed the highest concentration of MgO and CaO, and higher purity being present only the crystalline phases of the atapulgite and the quartz in its composition, and the diaphragms studied in this work with 75% of atapulgite clay presented the best results. The obtained results showed that the diaphragms studied in this work with 75% of atapulgite clay presented the best results. Among these, the D4 diaphragm with 75% attapulgite Basf presented results closer to Tephram® obtaining a soda concentration of 15,36 g/L and the lowest content of sodium chlorate in the cell liquor (0,33 g/L).