A critical review on the application of pyrite in constructed wetlands: Contaminants removal and mechanism

Pyrite is increasingly employed as a substrate in constructed wetlands (CWs), exhibiting outstanding denitrification and phosphorus removal efficient, and demonstrating superior removal efficacy for emerging pollutants (e.g., antibiotics). Nevertheless, the removal mechanisms of diverse pollutants in pyrite-substrate CWs remain in a "black box". The iron and sulfur transformation in the pyrite-based CWs significantly contribute to the removal of various pollutants, a concept elaborated in this review through analyzing the elemental cycles associated with the biochemical processes. In the pyrite-based CW, the highest removal of total nitrogen, total phosphorus, and COD achieved 95.05 ± 1.07 %, 97.4 ± 2.1 %, and 96 %, respectively. Notably, iron autotrophic, sulfur autotrophic, and ferric ammonia oxidation processes are pivotal for nitrogen removal, while the primary phosphorus removal mechanism involves iron hydroxide adsorption. Furthermore, reactive oxygen species (e.g., ·OH) generated through pyrite-activated molecular oxygen is crucial for removing recalcitrant emerging micropollutants, and this abiotic process exhibited more effective in mitigating the accumulation of antibiotic resistance genes. Overall, the pyrite-based CW is anticipated to achieve synergistic and efficient removal of multiple pollutants, representing a matter of considerable engineering significance.