A research group led by Prof. Chaoxu Li from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS), has revealed that biological nanofibrils could efficiently extract valuable metal elements from water.
Many valuable metals like Au, Ag, Li and U are vital to high technology and modern industry. The terrestrial mineral reserves of these metals are generally very limited. Some also suffer from high mining costs. Most of these valuable metal ions can be found in the ocean. Low-cost and high-efficiency adsorbents are still the key to the development of extracting these metals from seawater.
Their findings were published in ACS Nano on August 15.
In recent years, the group has conducted a lot of research on the exfoliation and self-assembly of biological nanofibrils. They found cyanoethyl substitution could enable rapid exfoliation of cyanoethyl cellulose nanofibrils by mild shear. Up to 90 per cent of the cyanoethyl cellulose nanofibrils were exfoliated within 30 min.
What they found with nanofibrils
They recently found that cellulose fibrils were preferentially exfoliated from the lignin-poor layer of secondary cell walls of balsa wood during an in-situ amidoximation process. These fibrils filled the wood cell tracheids.
The resultant woods could serve as efficient and high-pressure filtration membranes to capture aquatic uranium ions. This is similar to a typical cascading filtration when aligning the cell tracheids perpendicular to the flow. It enabled a rejection ratio of over 99 per cent and flux ~920 L m-2 h-1 for a two mm-thick free-standing membrane under 6 bar pressure.
“This study not only provides an in-situ approach to producing biological nanomaterials. It also offers a sustainable route for high-efficiency extraction of aqueous uranium,” said Prof. Mingjie Li, one of the study’s corresponding authors.
In their review published in Exploration on July 11, they reported that functional groups (e.g., carboxyl, amino, phosphonate and hydroxy) of biological nanofibrils enabled chemical reduction and capture of noble metal ions (e.g., Au, Ag and Pt) from water. That provides a green and sustainable route for noble metals recovery.
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