Eficiência da logística reversa no beneficiamento do resíduo de caulim da província pegmatítica da Borborema PB/RN, em unidade piloto de hidrociclonagem.

Abstract

Among the minerals in the Borborema Pegmatitic Province stands out kaolinite, a clay mineral, which usually has white color and several applications, mainly in the production of paper, ceramics, paints and others. In the extraction and improvement processes, more than 70% of the residues are generated, which still contain relevant percentages of kaolinite. The objective of this study was to study the concentration of kaolinite concentrate in hydrocyclone and the dispersion of kaolinite pulps in laboratory tests. The purpose of this study was to recover the kaolinite concentrate present in these residues through the reverse logistics principle. The main parameters studied in the hydrocyclone lab tests were: Aperture of the apex, vortex finder diameter, flow rate, pressure in pulp feed and percentage of solids. The laboratory dispersion tests were performed on a mechanical stirrer of up to 5,000 rpm and a beaker with a capacity of 500 mL and using Stokes's Law to determine the degree of dispersion. Using as pH regulators: hydrochloric acid, sodium hydroxide, sodium carbonate and calcium oxide. As dispersants: sodium hexametaphosphate and sodium silicate. The parameters studied were: pulp pH, speed and agitation time, conditioning time, percentage of solids, type and concentration of dispersants. The best hydrocyclone results were obtained with the following parameters: the opening of the apex in 12 mm, the diameter of the vortex finder in 25 mm, the percentage of solids in 20%, and the feed flow of 5,664.57 L.h-1. Under these conditions, the classification efficiency of more than 99.0% of particles smaller than 200 μm (0.074 mm) present in the overflow was obtained. The best results of the laboratory dispersion tests were obtained in: pH 9.0, agitation speed of 750 rpm, agitation time and conditioning time of 2.0 and 7.0 min, respectively, and percentage of solids of 35%.The hydrocyclone test with the best operating conditions and with pH adjustment obtained a classification efficiency of more than 90.0% of particles smaller than 200 μm and more than 79% of particles smaller than 325 μm (0.044 mm) in the overflow. (XRD) and X-ray diffraction (XRD), respectively, confirmed the presence of kaolinite concentrate in the studied waste, with contents of 59.8% SiO 2 and 39.9% of Al2O3. Regarding the efficiency of the hydrocyclone, the mass recovery was 78.8%, thus confirming that hydrocyclone is an efficient equipment in the classification of kaolinite concentrate. The dispersion gradient of kaolinite particles is significantly influenced by the medium and percentage of pulp solids. Regarding pH regulators, calcium oxide was the one that mostly affected the degree of dispersion compared to the other additives used. The use of chemical dispersants such as sodium hexametaphosphate and sodium silicate was poorly efficient in relation to the increased degree of dispersion of kaolinite particles.