Landfill-mined-soil-like-fractions and red mud as anthropogenic resources in polypropylene composites

Growing concerns over the threat to the geoenvironment from the disposal of municipal solid waste and industrial byproducts created an alarming situation. Hence, their utilization as Anthropogenic (manmade) Resources (read as AnthRes), especially those being generated in millions of tons, such as landfill-mined-soil-likefractions (LFMSF) and red mud (RM), become unavoidable. However, the existing utilization pathways raise questions over their environmental sustainability as they would not control the leaching of microplastics, salts, and heavy metals from these materials. To overcome this situation, the utilization of LFMSF and RM as fillers in manufacturing the polymer composites, which can isolate them from the outside environment, was proposed. In this context, the influence of the most significant parameters like (i) filler content (FC) and (ii) melt-mixing processes on the mechanical, thermal, and morphological characteristics of polypropylene composites were investigated. It was observed that FC and the presence of fiber-like organic matter in LFMSF would significantly influence the mechanical properties of the composites. Subsequently, mathematical models that can be employed for predicting the influence of the above-mentioned parameters on the mechanical properties were developed. Moreover, batch experiments were performed to obtain the leaching characteristics, which revealed that the concentrations of leachable elements from the composites reduced by over 98% as compared to their respective fillers indicative of effective bonding between the polypropylene matrix and filler particles. Hence, the present study established that the LFMSF and RM can be utilized as AnthRes in polymer composites for sustainable development without harming the geoenvironment.