The presence of heavy metals in the industrial effluents has recently been a challenging issue for human health. Efficient removal of heavy metal ions from environment is one of the most important issues from biological and environmental point of view, and many studies have been devoted to investigate the environmental behavior of nanoscale zerovalent iron (NZVI) for the removal of toxic heavy metal ions, present both in the surface and underground wastewater. The aim of this review is to show the excellent removal capacity and environmental remediation of NZVI-based materials for various heavy metal ions. A new look on NZVI-based materials (e.g., modified or matrix-supported NZVI materials) and possible interaction mechanism (e.g., adsorption, reduction and oxidation) and the latest environmental application. The effects of various environmental conditions (e.g., pH, temperature, coexisting oxy-anions and cations) and potential problems for the removal of heavy metal ions on NZVI-based materials with the DFT theoretical calculations and EXAFS technology are discussed. Research shows that NZVI-based materials have satisfactory removal capacities for heavy metal ions and play an important role in the environmental pollution cleanup. Possible improvement of NZVI-based materials and potential areas for future applications in environment remediation are also proposed.
With the rapid development
of industry, heavy metal pollution has
become a potential hazard to public health and the ecological system.
Herein, molybdenum disulfide coated Mg/Al layered double hydroxide
composites (LDHs@MoS2) were prepared via a simple hydrothermal
method and applied for the adsorption of Cr(VI) from a water solution.
The removal capacity of Cr(VI) on LDHs@MoS2 reached 76.3
mg/g at pH = 5.0, and the removal process relied on ionic strength
and pH. The results confirmed that the uptake of Cr(VI) on LDHs@MoS2 followed a spontaneous endothermic process. In contrast to
the LDHs, LDHs@MoS2 showed excellent chemical stability,
which was beneficial for practical applications. Specifically, the
coexisting ions had little influence on the uptake of Cr(VI). The
interaction of Cr(VI) with the LDHs@MoS2 composites was
mainly controlled by electrostatic attraction and outer-sphere surface
complexation. The findings can provide new insights into the uptake
of heavy metal ions in a natural aquatic environment pollution cleanup.
Metal/semiconductor composites are promising catalysts with superior catalytic activity. In this work, a Cu/CuO-Ag composite with structure that consisted of Ag and CuO nanoparticles (NPs) decorated on the surface of Cu were fabricated via a facile in situ method. With characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and inductively coupled plasma atomic emission spectrometry (ICP-AES), the structure and components of the Cu/CuO-Ag composite were well-defined. The Cu/CuO-Ag composite exhibited superior catalytic activities for the reduction of 4-nitrophenol (4-NP) in the presence of NaBH with just a trace amount of Ag NPs (1.28 wt %). The reduction reaction is completed in 75 s with an apparent rate constant k of 4.60 × 10 s. The Cu/CuO-Ag composite also showed excellent durable catalytic stability, as no significant activity loss was detected in the consecutive five reaction runs. With the aid of the Sabatier principle and volcano plot, the opportune chemical adsorption energy of the reagent 4-NP on the Cu/CuO-Ag composite was inferred to be the key to its high reaction rate. The CuO NPs as a semiconductor with narrow band gap also could help the Cu/CuO-Ag composite to capture the electrons/hydride ions and increase opportunities for 4-NP to be reduced. Furthermore, the Cu/CuO-Ag composite exhibited outstanding activity on the oxidative degradation of methylene blue (MB). This work enriched the bimetal/semiconductor catalyst system and supplied new insight into the catalysis mechanism.
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