Mechanochemically Activated Microsized Zero-Valent Iron/Pyrite Composite for Effective Hexavalent Chromium Sequestration in Aqueous Solution

Abstract

The activity of pyrite (FeS2) and microsized zero-valent iron (mZVI) is greatly limited by the passivating layer. This study indicated that hexavalent chromium (Cr­(VI)) could be effectively sequestered by mechanochemically activated mZVI/FeS2 composite (MA-mZVI/FeS2), which was obtained from the mZVI/FeS2 mixture by mechanochemical technology. Compared with MA-mZVI and MA-FeS2, the Cr­(VI) removal performance of MA-mZVI/FeS2 was significantly improved at a mZVI/FeS2 molar ratio of 1:9. The effects of initial concentration, coexisting anions, reaction time, and initial pH on Cr­(VI) sequestration by MA-mZVI/FeS2 were investigated. During the removal process, the concentrations of different valence states of chromium and iron were measured to explore the Cr­(VI) removal mechanism. Based on the experiments and characterizations, surface sorption accounted for 41.38% and reduction accounted for 58.62% at the Cr­(VI) adsorption equilibrium of MA-mZVI/FeS2. The ball milling destroyed the passivating layer of MA-mZVI/FeS2, resulting in a rough surface. The corrosion of mZVI can be significantly accelerated by FeS2 due to the strong interaction between mZVI and FeS2 in MA-mZVI/FeS2, which led to the enhanced Cr­(VI) sequestration. The practical application indicated that MA-mZVI/FeS2 had good Cr­(VI) removal performance in real water samples. This study revealed that MA-mZVI/FeS2 can be a hopeful adsorbent for effective Cr­(VI) sequestration in aqueous solution.

Chemical Bond Bridging across Two Domains: Generation of Fe(II) and In Situ Formation of FeSx on Zerovalent Iron

“…A simple physical coating of FeS x on the ZVI surface could result in discontinuity across the two domains despite the fairly good conductivity they both possess. 11,12 To resolve this issue, one should ensure that the electrons can efficiently pass through the cross section. Chemical bonds could be a bridge to foster electron transport between the two phases.…”

Wastewater Treatment Using Activated Carbon Produced From Oil Shale

“…They concluded that the ecologically friendly alternative adsorbent created from CF-AC can be employed effectively to remove Cr and Pb(II) ions from tannery wastewater. ZVI was found to be excellent at removing pollutants from wastewater, such as toxic metal ions (Ullah et al, 2020., He et al, 2020). Extensive research work was conducted on removing Wastewater Treatment Using Activated Carbon Produced from Oil Shale metals from wastewater using ZVI stabilized on carbon material, (Qu et al, 2017;Zhou et al, 2014;Congbin et al, 2021).…”

Graphene‐Oxide‐Coated, Polypyrrole‐Supported, Nano Zerovalent Iron Nanocomposites for Adsorption of Hexavalent Chromium from Wastewater

“…Cr (VI) is highly water soluble and toxic than Cr (III). [11] The maximum permissible limit for Cr (VI) in water is 0.1, 0.05 and 0.01 mg/L has been recommended by the World Health Organization (WHO), US Environmental Protection Agency (USEPA), and the Central Pollution Control Board (CPCB) India, respectively. [12,13] Long-term exposure to hexavalent chromium more than the permissible limit can cause nausea, nervous disorder, kidney failure, liver diseases, and cancer.…”

“…Chromium exists in water as hexavalent chromium (Cr (VI)) and trivalent chromium (Cr (III)). Cr (VI) is highly water soluble and toxic than Cr (III) [11] . The maximum permissible limit for Cr (VI) in water is 0.1, 0.05 and 0.01 mg/L has been recommended by the World Health Organization (WHO), US Environmental Protection Agency (USEPA), and the Central Pollution Control Board (CPCB) India, respectively [12,13] .…”