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The adsorption–desorption behavior of 2,4-dichlorophenol on microplastics in waters with different salinity
Summary
Researchers found that microplastics most efficiently adsorb the chlorinated pollutant 2,4-dichlorophenol in freshwater and release it more readily in saltwater, suggesting that as contaminated microplastics travel from rivers to estuaries and oceans they may offload their toxic cargo into new marine environments.
Microplastics may play an important role in the migration of contaminants. Meanwhile, drastic changes in water salinity significantly impact adsorption or desorption. The present work investigated the adsorption and desorption of 2,4-dichlorophenol (2,4-DCP) on microplastics in different salinities which were simulated by river water (0.3‰), lake water (15‰, 35‰ and 70‰) and sea water (15‰, 35‰ and 70‰), and was monitored by quartz crystal microbalance (QCM) and batch experiment. Furthermore, ATR-FTIR and Raman’s analysis were performed for microplastics before and after adsorption in different water systems, which provided evidence of 2,4-DCP linkage on microplastics. The mass of 2,4-DCP adsorbed on the microplastics showed the highest in river water (0.92 µg cm−2) and desorbed more and faster in 35‰ sea-salt water, which means that the most efficient adsorption was achieved in freshwater and slightly decreased in seawater. The influence of salinity on the adsorption of 2,4-DCP may be due to the electrical double layer, and ions from lake and sea salt may also compete for the adsorption sites on the surface of microplastics. The findings of this study will contribute to a deeper understanding of the fate of contaminants adsorbed on microplastics in arid regions and estuary environments, which are subject to rapid changes in salinity.