Interactions between humin and potentially toxic metals: Prospects for its utilization as an environmental repair agent

Abstract

The disposal of potentially toxic metals in aquatic systems is an issue that mainly involves densely populated regions that dump these contaminants into the environment, either directly or indirectly. Substances that are able to interact with these metals and affect their disposal, transportation and bioavailability are of significant environmental interest. Humin, which represents a fraction of humic substances, exhibits important characteristics, being capable of affecting the bioavailability of potentially toxic metals in the environment. This study assessed the interaction between humin and potentially toxic metals with a view to humin's use as chelating resin in repairing contaminated matrices. To this end, humin samples were extracted from soils that were collected in different parts of Brazil (Southeast and Northeast). The structural characteristics of the humin samples extracted presented significant differences, including differences in their organic material content. The results of adsorption studies showed similar kinetic adsorption behavior (pseudo second order) for the different humin samples, exhibiting high adsorption for all the potentially toxic metals studied (Cu²⁺, Cr³⁺, Pb²⁺, Cd²⁺ and Ni²⁺). In situ application demonstrated that humin could be used as a chelating resin for matrices that had been contaminated by potentially toxic metals.