Comparison of Different Procedures for Separating Microplastics from Sediments

Abstract

The separation of microplastics from environmental matrices is still challenging, especially for sediments where microplastics can accumulate affecting benthic organisms. Many authors have adopted different procedures, but their effectiveness has been rarely compared. The present study aims to compare the recovery rate of three different methodologies for the separation of dense microplastics from fine sediments and provide insights about contamination processes occurring in microplastic separation techniques. The protocols tested are a density separation method with NaCl and NaI, a density separation with NaI followed by a centrifugation step, and a digestion method with 10%KOH (m/v). The recovery yields of two high-density polymers of three different dimensional classes were tested. The highest recovery rate was reported for the first protocol. However, this method proved to be expensive, and unsatisfactory results were found when using merely NaCl. The digestion method was the one that was proven to be simple, reproducible, and affordable. The contamination tests highlighted as multiple filtration steps can increase the number of fibers deriving from airborne contamination. Since a unified approach for microplastic separation from sediments is still not selected, this study is of paramount importance as it provides data about the reliability of different methods widely adopted.

Occurrence of Microplastics in Kemena River and Niah River of Sarawak, Malaysia

“…Interestingly, the frequency of smaller microplastics in river water samples from both the Kemena and Niah rivers was consistently higher than in sediment samples. This observation is consistent with previous research, which suggested that buoyant plastic particles with a lower density than water can remain suspended in the water column, while denser particles can settle down onto the river bed and eventually sink into the sediments [21,22]. The higher percentage of the smallest microplastics detected in the sediment samples of the Kemena and Niah rivers highlights the fact that smaller plastic particles are more prone to migrate into sediments and deep water.…”

“…Furthermore, the size distribution of microplastics in river water and sediments highlights the different processes that control their transport and fate in the environment. [21,22].…”

Study on the Extraction Method of Microplastic System in Textile Wastewater

“…The NaI solution showed the highest recovery of 91.2% (PET), 93.7% (PA), and 91.7% (PU) for the separation of textile microplastics among all tested solutions. However, NaI is relatively expensive, and its solution is hazardous to the environment [ 58 ]. In addition, during the testing process, it was also found that NaI is highly oxidizing, and its use can lead to oxidation of the filter membranes to yellow and black colors, which has a greater impact on the subsequent visual identification and qualitative analysis ( Figure 10 ).…”

Approaches for Sampling and Sample Preparation for Microplastic Analysis in Laundry Effluents

“…(3) The efficiency of MPs isolation is inversely proportional to particle size; the smallest proportion of isolated particles are those with smaller dimensions [135]; (4) Due to their hydrophobic nature, the particles often coalesce into agglomerates to which various pollutants and microorganisms are adsorbed and form biofilms [41].…”