Synergistic effects of Fe-based nanomaterial catalyst on humic substances formation and microplastics mitigation during sewage sludge composting

Abstract

In this study, a novel Fe-based nanomaterial catalyst (Fe⁰/FeS) was synthesized via a self-heating process and employed to explore its impact on the formation of humic substances and the mitigation of microplastics. The results reveal that Fe⁰/FeS exhibited a significant increase in humic acid content (71.01 mg kg^-1). Similarly, the formation of humic substances resulted in a higher humification index (4.91). Moreover, the addition of Fe⁰/FeS accelerated the degradation of microplastics (MPs), resulting in a lower concentration of MPs (9487 particles/kg) compared to the control experiments (22792 particles/kg). Fe⁰/FeS significantly increased the abundance of medium-sized MPs (50-200 μm) and reduced the abundance of small-sized (10-50 μm) and large-sized MPs (>1000 μm). These results can be attributed to the Fe⁰/FeS regulating the ▪OH production and specific microorganisms to promote humic substance formation and the degradation of MPs. This study proposes a feasible strategy to improve composting characteristics and reduce contaminants.

Keywords: Composting; Fe(0)/FeS; Humification process; Microorganism; Pollutant.