Feasibility studies to use construction waste in the sorption of Pb ²⁺ , Cd ²⁺ , Cr ³⁺ and As ⁵⁺

ABSTRACT

This study evaluated the retention capacity of Pb²⁺, Cd²⁺, Cr³⁺ and As⁵⁺ per two types of soil, a clayey Latosoil and a sandy soil, by construction waste and mixtures containing 70% of soil and 30% of construction waste’s particles. For this, batch equilibrium tests were performed with samples of the five sorbents (construction waste, clayey soil, sandy soil, mixtures of clayey soil-construction waste and sandy soil-construction waste) added to monospecie solutions of lead, cadmium and chromium in the form of nitrate; and arsenic in the form of sodium arsenate, allowing the evaluation of how each element interacted with each sample. Five batches of samples were tested, in triplicate, with the same sorbent solution ratio, 1:20, and the concentrations of the solutions varied. Freundlich and Langmuir’s theoretical sorption curves were used to adjust the pairs of data points, the equilibrium concentration of solute in the solution (C_e) versus the solute mass sorbed per soil mass (S). The results allow concluding that the construction waste had greater ability to absorb Pb²⁺, Cd²⁺ and Cr³⁺. As⁵⁺, however, is more strongly sorbed by the clayey soil and by the mixture clayey soil-construction waste. The sorptive processes of Pb²⁺, Cd²⁺, and Cr³⁺ differ from the sorptive processes of As⁵⁺, because the first ones behave as cations in the soil, while the latter behaves as oxyanion. Finally, the clayey soil showed greater sorption capacity than the sandy soil for all the metals studied, as clayey soil has a higher organic material content.

Keywords:
sorption; construction waste; heavy metals; contamination; batch equilibrium tests