Facile microplastic recovery in soil using temperature-driven phase transition of saturated fat: Optimization and evaluation

Abstract

Extracting microplastics (MPs) from soil matrices is challenging due to their heterogeneous distribution and the lack of standardized recovery techniques. Addressing this, we introduce a cost-effective and eco-friendly method utilizing the temperature-driven phase transitions of saturated fats for efficient and accurate MP separation. Among the evaluated saturated fats - butter, lard, and coconut oil - coconut oil demonstrated a 100% recovery of five MP types (LDPE, PP, PS, PET, and PTFE) from soil across three consecutive cycles, owing to its solidification characteristics. The process was further examined by exploring the effects of agitation force and soil texture (sea sand and agricultural soil), where agitation force impacted efficiency, while soil texture remained insignificant. The technique utilizing coconut oil demonstrated high matrix retaining efficiencies for both soil matrices, signifying its ability to separate MPs without soil contamination. To ensure MPs' integrity, isopropanol was used for solidified coconut oil removal, which did not alter the MPs' pristine state, as validated by microscopy, FTIR spectroscopy, and Py-GC/MS. In comparison to prior methods, our approach significantly reduces both operating costs and environmental impact. Overall, our study paves the way for a sustainable and affordable solution to MP contamination in soils.