Carvão ativado obtido a partir de lodo de estação de tratamento de água aplicado na remoção de contaminantes

Abstract

The water treatment plant sludge (WTS) is a solid waste generated on large scales; and originates from water treatment processes that are responsible for the population supply of drinking water. In this context, the objective of this work was to evaluate the viability of WTS as a raw material in the production of activated carbon applied in the treatment of liquid effluents. The production of activated carbon from WTS was carried out through chemical activation using ZnCl2 and Ca(OH)2, followed by pyrolysis in an inert nitrogen atmosphere. After pyrolysis, part of the sample was subjected to acid leaching with HCl. The materials produced were characterized by the techniques of BET, DRX, FTIR, TGA, and DTGA. The results obtained showed that the activated carbon of WTS, after leaching by HCl, it presented a larger surface area (582 m².g-1 ) and greater thermal stability, which was the criteria for it to be chosen to continue the adsorption tests of methylene blue (MB) and nimesulide (NM). In the MB adsorption, the results of simultaneous optimization through the experimental planning technique in order to maximize the dye adsorption capacity and efficiency were 9.38 mg.g-1 and 94.65%, respectively. These conditions were obtained with the interaction of pH 7, contact time of 13.2 min, and 6.59 g.L-1 of adsorbent dosage. In the NM adsorption process, batch tests were carried out to determine the influence of pH and adsorbent dosage parameters and also studied the kinetic profiles, equilibrium isotherms and efficiency in synthetic hospital wastewater. The equilibrium time was reached in 120 min and the maximum amount adsorbed (qmax) of NM in the batch tests was 274.99 mg.g-1 . In addition, the adsorbent produced proved to be efficient in the treatment of hospital wastewater, obtaining an adsorption efficiency of 98.57%. Finally, NM adsorption was carried out in a fixed bed, obtaining a qmax value of 217.28 mg.g-1 , saturating in 250 min. Regarding the results obtained in this work, it is possible to state that the production of activated carbon from WTS is a good alternative for the use of such residue, producing an promising adsorbent in the treatment of effluents contaminated with MB and NM.