To effectively remove microplastics from salt, particularly sea salt, the most effective method identified involves first dissolving the salt into a liquid medium, such as water, and then applying a membrane technique enhanced by membrane backwashing. This approach has demonstrated significant efficiency in removing microplastics from synthetic seawater.
Understanding Microplastic Contamination in Salt
Microplastics are prevalent in various environmental matrices, including sea salt. Research has indicated the presence of these tiny plastic particles in sea salts, with observed levels around 1832 ± 40 particles per kilogram (kg). While a protocol exists to isolate and quantify these particles from solid salt samples, their removal typically requires the salt to be in a dissolved state.
The Membrane Technique for Microplastic Removal
Once salt is dissolved, creating a solution akin to synthetic seawater, the membrane technique becomes highly effective for microplastic removal.
- Principle: This technique involves passing the microplastic-laden salt solution through a semi-permeable membrane. The membrane acts as a physical barrier, allowing water and dissolved salt to pass through while trapping the larger microplastic particles.
- Effectiveness: Studies have shown that this method can achieve a remarkable removal rate, with 99.3% of microplastics removed from synthetic seawater. This highlights its potential for purifying salt solutions.
Enhancing Efficiency with Membrane Backwashing
To maintain the high efficiency and longevity of the membrane system, the membrane backwashing technique is crucial.
- Mechanism: Over time, microplastic particles and other contaminants can accumulate on the membrane surface, leading to fouling and reduced filtration efficiency. Backwashing involves periodically reversing the flow of water through the membrane, dislodging the accumulated particles and flushing them away.
- Benefit: This process significantly improves the overall efficiency of the membrane system, ensuring consistent high performance and extending the operational life of the membranes.
Summary of the Microplastic Removal Protocol
The development of a "facile and cost-effective protocol" using these techniques suggests a practical solution for addressing microplastic contamination in salt sources.
| Aspect | Description |
|---|---|
| Initial Step | For solid salt, it would need to be dissolved into a solution (e.g., water) to create a medium suitable for filtration, similar to how microplastics are removed from seawater. |
| Core Technique | Membrane Technique: Utilizes specialized membranes to physically filter out microplastic particles from the dissolved salt solution. This acts as a highly selective barrier. |
| Efficiency Boost | Membrane Backwashing: A crucial process where the flow through the membrane is reversed periodically to clean the membrane surface, preventing fouling and ensuring the sustained high removal efficiency (e.g., 99.3% reported for synthetic seawater). |
| Practicality | The overall protocol has been described as "facile and cost-effective," indicating its viability for large-scale application in purifying salt solutions. |
