Evaluation of platinum distribution between different soil components
Résumé
Purpose More attention has been given to the determination of background levels of platinum group element (PGE) in an urban environment. But, few studies have been conducted for its environmental behaviour. The necessity to understand the PGE behaviour in environment increases due to the increase in platinum (Pt) emissions. The aim of the study is to evaluate the adsorption and the distribution of Pt within soil and sediment components. This study investigated the Pt adsorption on kaolinite, hematite and humic acid. Materials and methods A batch experiment was used to determine sorption of Pt. The experiments were carried out on the three solids and on two mixtures of iron oxide and kaolinite, with two ratios 25:75 and 75:25. An elemental distribution of Pt was determined on the mixtures iron oxide–kaolinite by micro-X-ray fluorescence. Results and discussion The highest concentrations of Pt were found on kaolinite, followed by hematite and humic acid. Kaolinite exhibited the highest adsorption capacity. The sorption capacity of both mixtures was lower than that of kaolinite and iron oxide. Moreover, the shape of isotherms, for both mixtures, tends towards that of kaolinite. The elemental distribution maps of mixtures showed, for both ratios, a high enrichment of kaolinite with Pt opposite to a slight enrichment of hematite. Conclusions The results showed that Pt is adsorbed mainly on kaolinite, which suggests that Pt was mainly associated with clay in soil. The results allowed the evaluation of the impact of the matrix of soil or sediment on the ability to retain or promote Pt dispersion in an urban environment.