Assessment of the use of tropical peats as local alternative materials for the adsorption of Pb, Zn and Cd: An equilibrium study

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 (qm) 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.