Polymer quantification using the Rock-Eval® device for identification of plastics in sediments

Abstract

In this work, artificial thermal degradation experiments using the Rock-Eval® device were performed on selected polymer microsphere samples (PE, PP, PE100, PA6, PA11, PFA and PET). The main idea of this work is first to create a database of different polymer standard responses using the specific Rock-Eval® FID/IR peak signals. Several specific Rock-Eval® parameters are now defined to characterize each polymer family. For instance, each polymer is characterized by specific quantified parameters like Total HCpolymer, Total COpolymer, TotalCO2polymer, Tpeakpolymer, among others. This study attempts to demonstrate if this quick thermal degradation method can be also used to characterize the plastic contents (detection, type, and quantity) in sedimentary samples. Results indicate that each investigated polymer shows specific Rock-Eval® parameters that can be considered as useful characteristics of polymer families (mainly Tpeakpolymer, TOCpolymer, PCpolymer, RCpolymer, total HCpolymer, total COpolymer and total CO2polymer parameters). Samples containing different mineral matrices (e.g. sand, shale, marl and carbonate) were also mixed with polymers at different concentrations varying between 0.2 and 4.2 wt%. These composite samples were also analyzed in order to evaluate their thermal degradation comparing their specific Rock-Eval® FID/IR signatures. For example, most composite samples show an excellent linear correlation between TOC, PC, RC, total HC, CO and CO2 parameters versus the amount polymer at different concentrations. Although more work is still needed, a methodology is here proposed to distinguish and quantify the presence of plastics in the environment applying the proposed polymer Rock-Eval® database.