دانلود رایگان مقاله انگلیسی حذف فلزات سنگین توسط غشاهای میانبار پلیمر - اشپرینگر 2018

Abstract

Heavy metals cannot be biodegraded and they remain in the environment until being removed. Thus, the removal of heavy metals from contaminated water is of special concern for the protection of human and aquatic lives. Studies on polymer inclusion membranes (PIMs) started more than 50 years ago and have shown outstanding separation performance of metal ions. The potential and capabilities of PIMs have made it more favorable than ion exchange and liquid-liquid extraction process. To achieve efficient transport of metal ions, different types of extractant with compatible base polymer have been successfully used along with suitable targeted metal ions. However, selectivity of metal ion is only limited to one type of metal ion based on the extractant used in PIMs. The present review describes the current literature on heavy metal removal using PIMs for the past 3 years. The compatibility of extractant with base polymer and plasticizer is discussed. Most of PIM studies used cellulose triacetate (CTA) and polyvinyl chloride (PVC) as the base polymer, and only a few studies have used other base polymers. These new base polymers have shown better PIMs in terms of stability and separation performance compared to the CTA- and PVC-based PIMs. Moreover, a new invention of dual PIM separation system has allowed simultaneous separation of multiple metal ions. Such improvement in PIM technology can speed up commercialization process and make it viable for large scale and industrial use especially in hydrometallurgy and wastewater treatment.

Conclusion and Future Trend

Although applications of PIMs have been expanding lately in many other areas including on chemical analysis and analytical applications, research on heavy metal removals using PIMs is still of interest. In this review, current works on PIMs for various metal ions have been highlighted. Base polymer, extractant, and plasticizer are the three important components in PIMs. Thus, choosing the right component will provide excellent selectivity and permeability of the PIM’s performance. It is noted that PVC and CTA are still popular base polymer used in PIMs. However, in the future, it is expected that the trend will changed as new polymers are discovered such as PVDF-HFP and rGO/CTA. These new base polymers have shown outstanding performance and stability compared to PVC and CTA. As for extractant, it is very crucial as it determines the selectivity of metal ions. Aliquat 336 and D2EHPA are the most popular extractants because of their plasticizing effects, but they are only suitable for certain targeted ions. In order to achieve high selectivity, the concentration of most commercial extractants must reached at least 30 wt%. Thus, finding an extractant that used less amount of concentration but giving similar performance will be a great advantage. Lastly, the transport system for PIM is important to allow the separation process between targeted ions. Recent years have successfully developed dual PIM system. This system has successfully transported two metal ions into their individual stripping compartment by leaving the third metal in the feed phase. This work demonstrates the versatility and capability of PIMs for industrial applications. Therefore, more researches on enhancing this system are expected in the near future.