Antimony (Sb) pollution is a serious environmental concern in mining-affected regions. The use of nanoparticles to extract such metallic species has piqued the interest of researchers in the last few decades. A recent study available in the journal Science of The Total Environment focused on developing a reduced graphene oxide/bimetallic nanoparticle composite for the simultaneous removal of Sb (III) and Sb (V) from mining wastewater.
Study: Simultaneous removal of Sb(III) and Sb(V) from mining wastewater by reduced graphene oxide/bimetallic nanoparticles. Image Credit: Sky Cinema/Shutterstock.com
Environmental Impacts of Antimony (Sb) Contamination
Antimony (Sb) is a heavy metallic element that is widely utilized as a polymer catalyst, acrylic dye, and alloy in a variety of industries. Because of this rapidly increasing consumption, Sb is extensively procured both directly and indirectly through various mining projects, resulting in Sb contamination of groundwater resources in many mining communities.
Increased Sb levels are a concern since Sb may cause severe environmental damage at elevated amounts, as well as health problems in both animals and humans. As a result, strategies for efficiently treating Sb containments in mining wastewater are necessary.
Current Methods for Sb Removal and their Limitations
Adsorption, membrane processes, solvent separation, reduction precipitation, and electrochemical treatment are now the most used procedures for removing dangerous metal(loid)s such as Sb. However, due to its reusability, ease of use, and high functionality, adsorption is often regarded as one of the most successful metalloid removal processes.
Due to its large specific surface area, graphene is an excellent option for Sb adsorption.
Bimetal oxides have the potential to be good adsorbents as well. For instance, Fe-Ni bimetallic nanoparticles retain not only the high affinity and oxidation characteristics of their parental Fe oxide, but also the catalytic capabilities of Ni, and, more crucially, tend to encourage adsorption synergistically rather than additively. However, one of the outstanding challenges with metallic nanoparticles is their proclivity for coagulation.
Integration of Graphene with Metallic Nanoparticles
Recently, researchers attempted to merge graphene with metallic nanoparticles to overcome both problems at the same time. A hybrid Fe3O4/GO material was successfully produced and employed for oxidizing and adsorbing Sb (III) to solve the problematic issue of adsorption from graphene oxide.
While the substances were encouraging in terms of Sb adsorption capacity, they were all manufactured using conventional wet chemistry methods. Secondary environmental damage was induced due to the high toxicity of the catalysts used in the fabrication process, limiting the broad-scale implementation of the composite nanomaterials.
Phyto-synthesized Graphene Oxide/ Bimetallic Nanoparticles
Using biologically produced reduced graphene oxide/bimetallic nanoparticles (rGO-Fe/Ni NPs), the researchers hoped to concurrently remove two prevalent Sb species, Sb (III) and Sb (V), from mining effluent. The removal efficacy of the generated hybrid was first assessed after exposure to solutions containing just Sb (III) or Sb (V), and then to combinations containing both Sb (III) and Sb (V).
Following that, sophisticated characterizations were employed to track changes in the surface characteristics of rGO-Fe/Ni NPs before and after Sb contact to present proof for the proposed removal process. Finally, rGO-Fe/Ni NPs were used practically to remove Sb and other heavy metals from mining waste.
Important Findings of the Study
This research found that by employing rGO-Fe/Ni, both primary Sb constituents could be eliminated from mine effluent simultaneously. In a procedure including both adsorption and oxidation, the hybrid rGO-Fe/Ni nanoparticles outperformed the individual components in terms of Sb (III) and Sb (V) extraction efficiency.
Sb (III) elimination was substantially more effective in the pH range of 5-9, but Sb (V) elimination was higher under acidic settings. The adsorption mechanism revealed that the elimination of Sb (III) and Sb (V) involves both physical and chemical adsorption. XPS and oxidation dynamics revealed that Sb (III) elimination also involves oxidation.
The reduced graphene oxide/bimetallic nanoparticles were also effective in eliminating Sb and a range of other toxic substances from mining effluent, showing that the material has a high potential for the practical cleanup of heavy metal polluted wastewaters.
Chen, W. et al. (2022). Simultaneous removal of Sb(III) and Sb(V) from mining wastewater by reduced graphene oxide/bimetallic nanoparticles. Science of The Total Environment. Available at: https://doi.org/10.1016/j.scitotenv.2022.155704