Optimization of a method used for extracting microplastics from an organic matter-rich matrix and isolated particles...

Optimization of microplastic (MP) extraction methods is still an active research topic. Although a number of studies have been conducted on the extraction of MP from various water samples, sewage sludge remains a relatively new entity. Being highly complex, sludge is not particularly friendly when it comes to the isolation of MP. This study focused on combining the two main methods used for the isolation of microplastics: digestion and density separation, and optimizing their conditions using dried sewage sludge, which has one of the most complex matrices. Moreover, after optimization of the method, it was adapted to isolate MP from different scale wastewater treatment plants (WWTP) dewatered sewage sludge. The color, shape and size of MP were evaluated. Fenton's reagent was used to remove organic matter (OM) followed by density separation with NaBr (1.53 g cm^-3) to remove inorganic matrices. The efficiency of OM removal varied from 6.76 to 63.38 % depending on the applied conditions. The study confirmed that the OM removal efficiency can be increased by adding additional H₂O₂ every hour of the reaction. Regardless of the applied conditions Raman spectroscopic analyze confirmed that Fenton's reagent had no significant effect on standard (HDPE, LDPE, PP, PA) MP particles. Therefore, the most efficient OM removal method was further applied, and MP were isolated from an environmental sample - sewage sludge. Regardless of the scale of the WWTP, the dominant shape of the particles was fragment, the color - transparent, and as the size of the particles decreased, their percentage increased.