Obtenção de geopolímero a partir de rejeito da lavagem de bauxita amazônica

Abstract

The state of Pará is the largest national producer of bauxite, representing 85% of the Brazilian production of the ore and, as a result of this large production, it also represents the largest accumulator of tailings from the processing of this ore, which are deposited in lagoons and/or dams. The intense presence of silico-aluminates in this material, such as kaolinite, for example, demonstrates the great potential for the civil construction industry, that is, the possibility of producing geopolymeric materials from this waste. Bauxite washing, after calcination, transforms into amorphous material, more specifically into metakaolinite, which can be further potentiated when mixed with other residues as an additional source of Al and Si, which in this case is the so-called kaolin flint. As the waste from the bauxite washing has a limited amount of kaolinite, calcined flint kaolin was added to increase the metakaolinite content, helping in the geopolymerization reaction process. The raw materials and geopolymeric samples underwent characterization, and the main analyzes involved were: X-ray fluorescence (FRX), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Compressive strength tests were also carried out on the geopolymeric samples to assess the degree of polymerization, since the more polymerized the structure is, the greater the resistance. After 28 days of curing, the geopolymeric paste in the 80_RLBC formulation reached a compressive strength of 36 MPa and, of the 90_RLBC formulation, approximately 23 MPa at 28 days. The best results were obtained with samples activated with 9 mol/l of NaOH in the mixture with sodium silicate. The results obtained through the characterization analyzes of the samples demonstrated that the waste from the washing of bauxite and calcined flint kaolin, when activated with sodium hydroxide and sodium silicate, are a viable alternative for the production of geopolymeric materials