Influence of various production methods on the microplastic contamination of sea salt produced in Java, Indonesia.

The extensive research on microplastics (MPs) in the last years has shown that it is not just an environmental problem anymore. As it can also be found in human food, it poses a potential risk for human health and food safety. Especially sea salt, which is produced by the evaporation of seawater, including its microplastic contamination, has been reported with different levels of MP contamination. Therefore, in this preliminary study, we investigated if different solar evaporation methods (traditional, geomembrane, and tunnel) influence the concentration of microplastic particles in sea salt production in Indonesia, one of the countries with the highest estimated level of plastic waste input into the ocean. The results show a significantly higher MP contamination in sea salt produced traditionally compared to the geomembrane and tunnel methods.

Comparative study of the influence of linear and branched alkyltrichlorosilanes on the removal efficiency of polyethylene and polypropylene-based microplastic particles from water.

Microplastics are a global environmental pollution. Due to this fact, new solutions are needed to reduce the amount in various aquatic environments. A new concept introduced by Herbort and Schuhen from the year 2016 describes the agglomeration of microplastics in water using silicon-based precursors. In the study presented here, alkyltrichlorosilanes with different linear and branched alkyl groups and a chain length between 1 and 18 carbon (C-) atoms are investigated for their suitability to fix microplastics (mixtures of polyethylene (PE) and polypropylene (PP)) and to form larger agglomerates. As the alkyl group has a major influence on the reaction rate and agglomeration behavior, we present here the extensive data collection of the evaluation of the best case. The removal efficiency is determined gravimetrically. The reaction behavior and the fixation process are characterized by hydrolysis kinetics. 29Si-MAS-NMR spectroscopy, IR spectroscopy, and thermogravimetry (TGA) are used to characterize the chemical composition of the agglomerates. Finally, the use of optical coherence tomography (OCT) allows the visualization of the formed agglomerates. The results show that the different alkyl groups have a strong impact on the suitability of the alkyltrichlorosilanes for the agglomeration, as they influence the hydrolysis and condensation kinetics in water and the affinity to the microplastics. Best suited for microplastic removal were intermediate chain length between 3 and 5 C-atoms.

A new approach for the agglomeration and subsequent removal of polyethylene, polypropylene, and mixtures of both from freshwater systems - a case study.

Based on a new concept for the sustainable removal of microplastics from freshwater systems, a case study for a pH-induced agglomeration and subsequent removal of polyethylene and polypropylene particles from water is presented. The two-step-based process includes firstly a localization and secondly an aggregation of microplastic particles (250-350 µM) in a physicochemical process. The research describes a strong increase in the particle size independent of pH of the aquatic milieu induced by the addition of trichlorosilane-substituted Si derivatives. The resulting Si-based microplastic aggregates (particle size after aggregation is 2-3 cm) could be easily removed by use of, e.g., sand traps. Due to the effect that microplastic particles form agglomeration products under every kind of process conditions (e.g., various pH, various polymer concentrations), the study shows a high potential for the sustainable removal of particles from wastewater.