Síntese de geopolímeros a partir da caulinita, metacaulinita e espodumênio e sua aplicação como adsorvente de amoxicilina

Abstract

In this work, geopolymers were synthesized from 3 different precursors: kaolinite, metakaolinite and spodumene. For kaolinite and metakaolinite, the synthesis of the geopolymers took place using a 11.75 M sodium hydroxide solution and the structure-directing agent hexadecyltrimethylammonium bromide (CTAB) in percentages of 0, 10, 20 and 30 wt%. Curing time was 5 days and then the materials were dried in an oven at 80 °C for 24 hours. For spodumene, a hydrothermal synthesis was carried out with a 19.58 M sodium hydroxide solution at a temperature of 200 °C for 3 hours. After this period, the material was dried in an oven for 17 hours. In the case of spodumene, it was found that this material is not suitable to produce geopolymer without previous treatment, since, due to its stability, it was not possible to promote the breakdown of its structure using only the basic solution, and the use of hydrothermal treatment favored the formation of products other than geopolymer. In the case of kaolinite and metakaolinite, both had a large amount of quartz, as evidenced by the thermogravietry, X-ray fluorescence and X-ray diffraction analyses carried out, which prevented the geopolymerization reaction from happening to a great extent, as could be seen by the permanence of peaks related to quartz in the diffractograms of geopolymeric materials. These systems also presented sodalite formation. The geopolymers synthesized showed small values of superficial area – between 4 and 12 m2 g-1, but it was possible to verify that the presence of CTAB influenced the diameter of the pores formed, moving them to slightly larger values and also causing greater uniformity around the diameters. In general, it was found that despite being quite heterogeneous, the materials synthesized from kaolinite and metakaolinite show very promising results as adsorbent agents for amoxicillin, with emphasis on Geo20 (kaolinite geopolymer with 20 wt% CTAB), which presented qmax = 199 mg g-1.