Remoção de poluentes emergentes por adsorventes desenvolvidos a partir de resíduo sólido de estação de tratamento de água

Abstract

The increasing presence of pharmaceutical compounds in aquatic environments has caused significant environmental impacts. Conventional treatment methods face challenges at the industrial scale, while abundant and low-cost adsorbents, such as industrial process residues, offer a sustainable alternative for the removal of pharmaceuticals. In this study, adsorbent materials were developed from sludge generated by the water treatment system of a thermoelectric power plant. Adsorption studies were carried out using unmodified sludge (RPL), chemically modified sludge with dodecyl trimethylammonium chloride (RMQ), and thermally modified sludge (RMT). The materials were applied for the removal of ibuprofen, diclofenac, hydroxychloroquine, and losartan in aqueous medium. Different characterization techniques were performed for the adsorbents. X-ray fluorescence (XRF) revealed the presence of Si, Al, and Fe as the predominant elements. Fourier transform infrared spectroscopy (FTIR) showed vibrational bands associated with Si-O-Si, Si-O-Al, Si-O, Si-OH, and CH₂ groups, while X-ray diffraction (XRD) indicated similar patterns among the materials, with crystalline phases such as SiO₂ and NaAlSi₃O₈. The chemical modification of the residue promoted a moderate increase in surface area and led to an improvement in the removal efficiency of the pharmaceuticals, with values higher than 70.00%.The adsorption capacities obtained in batch adsorption studies were 101.43 mg g-1 for losartan, 73.77 mg g-1 for diclofenac, 24.81 mg g-1 for ibuprofen, and 39.25 mg g-1 for hydroxychloroquine. In fixedbed column adsorption studies, the adsorption capacities were 46.71, 51.70, 44.86, and 20.43 mg g-1 for hydroxychloroquine, losartan, diclofenac, and ibuprofen, respectively. Chemical regeneration of the adsorbents allowed their reuse for most pharmaceuticals, although a reduction in adsorption capacity was observed after successive cycles. The electrochemical degradation of the pharmaceuticals was evidenced by the reduction of the characteristic anodic peaks in the voltammograms, indicating a decrease in the concentration of electroactive species in solution. Ecotoxicity tests using pharmaceutical solutions resulted in EC50,48 h values of 3.81, 24.11, 175.50, and 53.92 mg L-1 for hydroxychloroquine, diclofenac, losartan, and ibuprofen, respectively. The results obtained in this study demonstrated the feasibility of using this residue due to its efficiency in removing pharmaceuticals and its potential applicability at an industrial scale. Furthermore, the reuse of this residue may contribute to reducing its environmental impacts.