Phosphogypsum-Modified PBAT Composite Films: Preparation, Mechanical Enhancement, and Impact of Aged Fragments on Soil and Tomato Growth

The increasing accumulation of phosphogypsum (PG), an industrial by-product, poses significant environmental challenges. In this study, phosphogypsum powder modified with silane coupling agent KH570 (KPG) was incorporated into poly (butylene adipate-co-terephthalate) (PBAT). Further, the composite film (PKPG) of KPG and PBAT was prepared by plastic thermoforming process. The structure, mechanical properties, and agricultural applicability of PKPG were systematically evaluated. Our results revealed that the inclusion of KPG enhanced the comprehensive performance of PBAT films. Pot experiments demonstrated that the aged PKPG fragments increased soil organic carbon and total nitrogen contents, and altered the soil microbial community structure and functional profiles. While 0.1% PKPG promoted tomato growth, 1% PKPG addition caused plant root stress and inhibited crop development. These results suggest that PKPG can simultaneously improve film performance and soil fertility, but careful control of application rates is necessary to avoid potential adverse effects on plant growth. Further long-term studies are needed to assess the ecological safety and optimize the application strategy for field.