Estabilização do chumbo por solidificação em cinzas de bagaço de cana incorporada em concreto

Abstract

The lead (Pb2+), despite being considered a toxic element causing health impairment, has a vast industrial usage. The disposal of industrially contaminated effluents has been contributing to a significant raise in the concentration of these metal ions in water, thus being a great source of waterbody contamination. In order to minimize the effects of these substances, a number of researches have been elaborated with the aim of developing new technologies to remove lead from industrial effluents. Considering the high cost when removing toxic metal ions from effluents, there is a current need of developing effective solutions with better economic viability, as an example, the adsorption of effluents using sugar cane bagasse ashes (CBA) as a biosorbent. While the results found in literature are considered satisfactory, a way to correctly dispose the lead contaminated biosorbent is yet to be found. Knowing that the CBA has pozzolanic properties, similar to the cement (binder portion of concrete) and, based on studies shown in the bibliography, it is possible to replace part of the cement for CBA. Thus, the assumption of incorporating the CBA, used as lead adsorbent, in the confection of concrete has been made. The CBA was used as a mineral addition to the concrete in percentages of 5%, 10%, 15% and 20% in relation to the cement mass according to the mix used. CBA adsorption tests were performed at concentrations of 100 mg.L-1, 200 mg.L-1 and 500 mg.L-1. Through thorough analysis, it was possible to place the 200 mg.L-1 solution as the solution with better adsorption efficiency for the CBA. Therefore, a lead adsorption process performed on a larger scale was carried out using CBA. To ensure the adsorption process, tests to detect the presence of lead in in natura ashes and in adsorbed ashes were performed. The results prove that the in natura ashes did not contain any amount of pré-existing lead in their compositions and after the adsorption process, the ashes were able to adsorb 99.94% of the lead. After the characterization of the materials, a mix proportion of 1:1.49:4.00:0.42 (cement:sand:coarse gravel:water) was defined, adding superplasticizer at a 0.3% ratio, compared to the cement mass. Before being incorporated into the concrete, the CBA was kiln dried. Later, cylindrical specimens were made to perform density, water absorption, voids content, compressive and tensile strength tests. After, concrete plates were produced to test the permeability of distilled water following the procedures of the NBR 16416, the permeated water was analyzed to detect the existence of lead in it, as a result, no amount of lead was detected by the device with a detection limit of 0.01 mg.L-1.