Identification, extraction of microplastics from edible salts and its removal from contaminated seawater

Abstract

Microplastics (MPs) present in edible salts may create a potential health hazard for humans. The occurrence of MPs in edible salts and their extraction procedure is limited. In this work, we have developed a facile and cost-effective protocol for the extraction and separation of MPs from the edible salt sample. The visual assessment was performed to identify the shape, size, number, and color of microplastic particles using light and fluorescence microscopy. The composition of the sample was analyzed by micro-Raman spectroscopy. A wide range of MPs were found: 1400 ∼1900 particles/kg in refined sea salt, 1900 ∼2300/kg in unrefined sea salts, and 200 ∼400/kg in rock salts. A relatively high number of MPs were found in sea salts rather than rock salts. Sheet type MPs with size 1 ∼ 4μm were observed in rock salts. The most common MPs were polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), nylon, and polystyrene (PS). Further, MPs were effectively removed from synthetic seawater with the help of a microfiltration membrane, which has the capability of arresting the transfer of microplastic particles into edible salts. Therefore the use of MF/UF pretreated brine from seawater desalination plant can be explored for MPs sea salt production at low cost.