Argila caulinita da região norte do Brasil: caracterização e aplicação como adsorvente de compostos orgânicos (btx) e oxiânions de cromo hexavalente

Abstract

Clays have a high technical-economic viability for diverse industrial applications. In certain regions of State of Pará, clays are abundant and their extraction occurs intensively, usually used in manufactures of ceramic artifacts. The use of modified clays as adsorbents in the remediation of contaminated water has been the subject of several studies. In this work, a kaolinite characterization and its application as adsorbent in the form "in natura" heat treated in the adsorption of BTX and after modification of its surface by catônico surfactant (HDTMA-Br) was studied, as adsorbent of hexavalent chromium oxyanions. In the study of adsorption of chromium (VI) a factorial design (DCCR) was used, applying variables such as pH and concentrations of surfactant. The clay from Icoaraci District (PA) was classified by sieving, as (NBR 7181). Fractions "in natura" (FR-NAT) and modified (FR-ORG) and (FR-TR), with particles smaller than 44 m and the modified materials were submitted to analysis: x- ray diffraction (XRD), x-ray fluorescence, ATG/DTA, electron microscopy (SEM), determination of surface area (SBET), mercury porosimetry, CTC and pH (pcz). The composition of the clay material were identified: quartz, kaolinite and illite/muscovite (I/M); SiO2 (59.6%) and Al2O3 (17.5%). The property values of: 21.8 SBET m2/g; pore size distribution in the mesopore and macropore region; CTC 17 (meq/100 g) and pHPCZ value equal to 4.3. The analyzes of ATG/DTA samples of organoclays showed that there was loading the clay surface by surfactant (HDTMA-Br). Samples thermally modified natural clay and showed no affinity for organic compounds (BTX). In the study of the adsorption of hexavalent chromium, a factorial design (CCRD) based on pH and concentration of surfactant was used. The adsorption of hexavalent chromium by natural clay was not satisfactory, but the chemically modified clay reached satisfactory values. From the statistical analysis of the adsorption data, only the concentration of cationic surfactant produced statistically significant effects in removing the adsorbate.