Removal of Microplastics from Waters through Agglomeration-Fixation Using Organosilanes—Effects of Polymer Types, Water Composition and Temperature

Abstract

Due to the fact, that microplastics are a global environmental problem, new ways for their removal from water, soil and air need to be developed. New materials in combination with easy to implement technologies for microplastic removal come into the focus of scientific studies and engineering, especially for application in water resources. In our comparative case study, the effects of water composition and temperature on the agglomeration-fixation reaction of microplastics using organosilanes were examined. We compared biologically treated municipal wastewater, seawater and demineralized water at temperatures ranging from 7.5–40 °C. Temperature variations and tested water compositions showed no negative effect on microplastic removal. The residues of the organosilanes remaining in the water after the fixation process were monitored using ICP-OES and DOC measurements. Only one of the organosilanes tested showed no dissolved residues in the waters. Microplastic encompasses a multitude of different types of polymers with different properties and surface chemistries. Therefore, we compared the efficiency of the process for polyethylene, polypropylene, polyamide, polyester, and polyvinylchloride as examples of common polymer types with different chemical compositions. A strong effect of the polarity of microplastics and organosilanes on removal efficiency was observed. The organic groups of organosilanes can be chemically adapted to different polymer types.

Microplastics in the Great Lakes: Environmental, Health, and Socioeconomic Implications and Future Directions

“…They found that the most effective methods out of those reviewed are membrane bioreactors (>99%), conventional activated sludge (98%), wastewater treatment plants (>95%), and algae adsorption (94.5%) . Another highly effective method not included in the review is agglomeration-fixation by organosilanes (monomeric silicone-based chemicals) which has an efficacy of up to 99.4% . Although effective removal methods exist, some experts fear that MP removal from the environment is too gargantuan a task.…”

“…18 Another highly effective method not included in the review is agglomeration-fixation by organosilanes (monomeric silicone-based chemicals) 96 which has an efficacy of up to 99.4%. 97 Although effective removal methods exist, some experts fear that MP removal from the environment is too gargantuan a task. The particles are extremely pervasive; they are present throughout bodies of water, soil, and even raining from the sky.…”

Tackling Marine Microplastics Pollution: an Overview of Existing Solutions

“…Another promising solution is represented by organosilanes, the use of which has been studied in the last few years for the specific removal of MPs from water (Herbort et al, 2018;Schuhen et al, 2019;Sturm et al, 2020Sturm et al, , 2021. Organosilanes consist of one organic group and three reactive groups.…”

“…Organosilanes consist of one organic group and three reactive groups. The organic group is able to attach to the surface of the microplastic and collect it in agglomerates, while the reactive groups form a solid hybrid silica gel thanks to a water-induced sol-gel process that entraps the microplastic (Sturm et al, 2021). The organic group can be adapted to different polymer types, making organosilanes effective in the removal of different plastics.…”

Photocatalytic collection and degradation of microplastics by self-asymmetric Pac-Man TiO2

“…Then, adding hybrid silica gels induces a sol-gel process, resulting in the fixation of microplastics into a three-dimensional networked hybrid silica gel form, which is subsequently removed from the system. 18,19 The principle of assembling microplastics to separate them has also been investigated with selfpropelling Au@TiO 2 microparticles, which exhibit rafts or clusters when interacting with passive particles (like SiO 2 or polystyrene microparticles). This rafting behaviour not only gave a physical understanding of the interactions between an active and passive particle 20,21 but allowed the capture and removal of microplastics of different sizes and geometry.…”