Preliminary Study of the Adsorption Capacity of Pb, Zn and Cd Through Zeolite and Organic Compost

Reactive materials have been used as a solution to prevent potentially toxic metal contamination stemming from mining waste disposal. These materials are characterized by a high cation exchange capacity (CEC) and a predominance of negative charges, favoring their potential utilization in metal cation immobilization. Therefore, the aim of this study is to compare the sorption capacity of common metals in mining areas (Pb, Zn and Cd) with zeolite, an inorganic material traditionally studied and used for this purpose, and compost, a low-cost organic material, that in comparison to zeolite, has been sparsely researched. Two Cuban commercial clinoptilolite zeolites were evaluated: natural zeolite (NZ) and NaCl treated zeolite (TZ). Two municipal solid waste-derived composts were also assessed with differences in the composting method: windrow (WC) and static pile (SPC). Batch equilibrium experiments showed that the selectivity of removal of TZ, WC and SPC followed the order Pb > Cd > Zn. The only exception was NZ (Pb > Zn > Cd). In general, all materials presented higher performances than Pb (with adsorption efficiency more than 95%). The SPC was revealed to be the best adsorbent of Pb, but with a similar removal percentage for the TZ. The TZ was significantly more efficient in retaining Zn. In the case of the Cd, the WC and TZ showed the highest removal percentage. These results suggest that compost, a low-cost byproduct, can adsorb a considerable concentrations of metals, and thus is able to compete with zeolites for use, isolated or combined with other materials, as an effective sorbent in metal contamination.