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

Eny Maria Vieira,Valéria Guimarães Rodrigues,Isabela Monici Raimondi,Jéssica Pelinsom Marques,Jacqueline Zanin Lima,Luiz Augusto Artimonti Vaz

doi:10.15446/esrj.v25n1.84276

Eny Maria Vieira, Valéria Guimarães Rodrigues + Show 4 more

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https://doi.org/10.15446/esrj.v25n1.84276

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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.

Highlights

Peat is formed by the decomposition of several plant materials in the waterlogged environments of marshes, bogs and swamps (Spedding, 1988; Zulkifley et al, 2016) and is present on all continents, from sea level to high altitudes (Joosten and Clarke, 2002)
The removal percentage of the three ions was dependent on the initial concentration, and higher removal occurred at lower concentrations, with maximum removal reached at the lowest concentration
In peat C (Figure 3a), the Pb adsorption was above 70% at all concentrations, while in LA (Figure 3b), the Pb removal ranged from 98.6 to 46.3%

Summary

Introduction

Peat is formed by the decomposition of several plant materials in the waterlogged environments of marshes, bogs and swamps (Spedding, 1988; Zulkifley et al, 2016) and is present on all continents, from sea level to high altitudes (Joosten and Clarke, 2002). Peats located in tropical and subtropical regions correspond to a small portion of the total: 35.80 million hectares (Andriesse, 1988; IPS, 2008). The typical characteristics of a tropical climate (high precipitation, high evapotranspiration and high average annual temperatures) directly affect the type of peat formed in this region. Climate has both direct (for example, via hydrology) and indirect (via the vegetation species; trees, containing woody material, are typically present in tropical regions, whereas sedges and Sphagnum moss are found in temperate regions) effects on peatlands. Tropical peatlands can be found on the entire African continent and in most of South America (notably Brazil and Uruguay), southern Florida, North Carolina and Southeast Asia (which contains the largest extension, approximately 57%, of tropical peat deposits) (Andriesse, 1988)

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