A sandwich-like nano-system developed recently could simultaneously remove heavy metals, mainly Cr(VI)/Cd(II), from contaminated water and soil.

WU Zhengyan’s study team from Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science conducted this research and their new technology was published earlier this week in ACS Applied Materials & Interfaces.

Now, a variety of nanomaterials based on carbon, clay, polymer, and metallic oxide have been fabricated to remove Cr(VI) and Cd(II) because of their high efficiency and simple procedure.

However, these nanomaterials were commonly used to remove Cr(VI) or Cd(II) separately rather than simultaneously because of the opposite zeta potentials of Cr(VI) and Cd(II), which became the dominant limitation factor for their application to remediate Cr(VI)/Cd(II)-contaminated water and soil.

Importantly, owing to the lack of ideal carrier, it was difficult to efficiently and conveniently collect the nanomaterials together with Cr(VI)/Cr(III) and Cd(II) from water especially soil, which was another bottleneck to restrict their engineering application.

"We want to fabricate a nanosystem to remove Cr(VI) and Cd(II) simultaneously in soil and water. What's more, it can be separated from wastewater and soil after treatment conveniently", said WU.

In their study, the novel nano-system with sandwich-like structure was synthesized via face-to-face combination of two pieces of waste cotton fabrics (CFs) carrying ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide (CFFM) respectively, and the obtained nano system was named FeS/CFFM/CF.

FeS/CFFM/CF could simultaneously remove Cr(VI) and Cd(II) from water, inhibit the uptake of Cr and Cd by fish and water spinach, ensuring food safety.

Besides, this technology could efficiently control migration of Cr(VI) and Cd(II) in sand-soil mixture, which was favorable to prevent their wide diffusion.

Importantly, FeS/CFFM/CF possessed a high flexibility and could be conveniently produced with needed scale and shape, and easily separated from water and soil, displaying a promising approach to remediate Cr(VI)/Cd(II)-contaminated water and soil and a huge application potential.

This research was supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the Science and Technology Service Programs of the Chinese Academy of Sciences, the Science and Technology Major Project of Anhui Province, and the Environmental Protection Project of Anhui Province.

Schematic illustration of mechanism. (Image by WANG Dongfang)