Application of adsorbents derived from waste in contaminated areas remediation is aligned with sustainable development goals and circular economy principles. As chemical activation can result in increased adsorption capacity, it is an alternative to improve the performance of materials and enable their use. This study evaluated whether activated compost derived from the organic fraction of municipal solid waste would be an efficient and low-cost adsorbent. Chemical activation was performed by impregnating 1 mol L-1 of phosphoric acid for 12 h at 25 °C. Characterization and batch equilibrium tests were carried out to confirm if chemical activation would positively affect the retention of lead (Pb) and cadmium (Cd). Surface functional groups and minerals were verified through Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffractometry (XRD) before and after batch equilibrium test. Removal percentages ranged from 52.49 to 91.22% for Pb (initial concentrations of 20.11 to 889.20 mg L-1) and from 13.33 to 87.13% for Cd (initial concentrations from 1.56 to 667.50 mg L-1). Compared to the original material, activation did not increase Cd adsorption capacity. However, was observed an improvement in adsorption performance for Pb between 76.86 and 443.30 mg L-1. The Langmuir isotherm best fitted the experimental data obtained both for Pb and Cd.

RESUMEN La turba es un material orgánico que se ha utilizado ampliamente como adsorbente eficiente y de bajo costo. Dado que muchos estudios tienden a centrarse en las turbas templadas, hay una falta de conocimiento sobre el mecanismo de adsorción de las turbas tropicales. Este trabajo investiga el uso de dos turbas brasileñas (Cravinhos - C y Luis Antonio - LA) de la cuenca del río Mogi-Guacu para la adsorción de plomo (Pb), zinc (Zn) y cadmio (Cd), con el fin de contribuir al uso de materiales locales y de fácil acceso para remediar sitios contaminados. Las turbas adsorbieron un alto porcentaje de cationes, especialmente cationes Pb (100,0-46,3%), mostrando la turba comercial C una mayor adsorción que la turba LA. La orden de eliminación fue Pb2+ > Cd2+ ≥ Zn2+ para C y Pb2+ > Zn2+ > Cd2+ para LA. Los datos de equilibrio por lotes para turbas y para todos los metales se ajustaron mejor a la isoterma de Langmuir, con capacidades de adsorción (qm) para Pb, Zn y Cd de 37,3134, 29,0674 y 21,2890 mmol kg-1 en turba C y 21,7391, 14,2550 y 3,6460. mmol kg-1 en LA, respectivamente, valores comparables a los de otras turbas y biosorbentes. Las turbas estudiadas se consideran materiales adsorbentes eficientes, alternativos y de bajo costo para estos metales. La proximidad de las turberas a áreas con alto potencial de contaminación requiere el uso de materiales locales para reducir los costos de remediación.

ABSTRACT Peat is an organic material that has been widely used as an efficient and low-cost adsorbent. As many studies tend to focus on temperate peats, there is a lack of knowledge about the adsorption mechanism of tropical peats. This paper investigates the use of two Brazilian peats (Cravinhos - C and Luis Antônio - LA) from the Mogi-Guaçu river basin for the adsorption of lead (Pb), zinc (Zn), and cadmium (Cd), in order to contribute to the use of local and easy access materials to remediate contaminated sites. The peats adsorbed a high percentage of cations, especially Pb cations (100.0-46.3%), with commercial peat C showing higher adsorption than peat LA. The removal order was Pb2+ > Cd2+ ≥ Zn2+ for C and Pb2+ > Zn2+ > Cd2+ for LA. The batch data for both peats and for all metals were better fit by the Langmuir isotherm, with adsorption capacities (q m ) for Pb, Zn, and Cd of 37.3134, 29.0674 and 21.2890 mmol kg-1 in peat C and 21.7391, 14.2550 and 3.6460 mmol kg-1 in LA, respectively, values comparable to those of other peats and biosorbents. The studied peats are considered efficient, alternative and low-cost adsorptive materials for these metals. The proximity of peatlands to areas with high potential for contamination necessitates the use of local materials to reduce remediation costs.