Evaluation of Municipal Waste Compost in Relation to the Environmental Retention of Heavy Metals

Abstract

This study investigates the performance of municipal compost as a heavy metal adsorbent for environmental protection systems. The performed assays test the effects of the pH (2–9) and contact time (5–250 min) on metal retention. To simulate leaching in natural systems, the soluble organic fraction was removed, leading to variations in the surface properties, including a 10% increase in the cation exchange capacity (CEC) and a 242% increase in the BET-specific surface area, accompanied by a small decrease in the surface charge (characterized by a less negative zeta potential values) of the washed municipal compost (WMC). Notably, these variations, which have not been found in previous research, yielded improved retention of Cu(II) and Zn(II) compared to raw municipal compost (RMC), attaining 96% retention for Cu(II) and 97% retention for Zn(II) at a pH of approximately 6.8–7.2 for a contact time of 120 min. The vast availability, cost-effectiveness, and resistance to desorption make municipal compost a viable option in a circular economy context for mitigating metal pollution across various environmental conditions. It is worth noting that this study can serve as a proxy for the expected outcomes in long-term exposure to environmental protection systems, enhancing the practical relevance of using compost for metal retention purposes.