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Phytoremediation, an ecological approach aimed at addressing polymetal(loid)lic-contaminated mining soils, has encountered adaptability challenges. Dominant plant species, well-suited to the local conditions, have emerged as promising candidates for this purpose. This study focused on assessing the phytoremediation potential of ten plant species that thrived in heavy metal(loid)-contaminated mining soils. This investigation covered nine heavy metal(loid)s (As, Cu, Cd, Cr, Hg, Ni, Pb, Sn, and Zn) in both plants and rhizosphere soils. The results revealed a significant impact of mining activities, with heavy metal(loid) concentrations surpassing the Yunnan Province's background levels by 1.06 to 362 times, highlighting a significant concern for remediation. The average levels of the heavy metal(loid)s followed the order of As (3.98 × 103 mg kg−1) > Cu (2.83 × 103 mg kg−1) > Zn (815 mg kg−1) > Sn (176 mg kg−1) > Pb (169 mg kg−1) > Cr (68.1 mg kg−1) > Ni (36.2 mg kg−1) > Cd (0.120 mg kg−1) > Hg (0.0390 mg kg−1). The bioconcentration factors (BCFs), bioaccumulation factors (BAFs), and translocation factors (TFs) varied among the native plants, indicating diverse adaptation strategies. Low BCFs and BAFs (ranging from 0.0183 to 0.418 and 0.0114 to 0.556, respectively) suggested a low bioavailability of heavy metal(loid)s. Among the species, both J. effusus and P. capitata showed remarkable abilities for As accumulation, while A. adenophora demonstrated a notable accumulation ability for various heavy metal(loid)s, especially Cd, with relatively high BCFs (1.88) and BAFs (3.11), and the TF at 1.66 further underscored the crucial role of translocation in preventing root toxicity. These findings emphasized the potential of these plant species in mine ecological restoration and phytoremediation, guiding targeted environmental rehabilitation strategies. [ABSTRACT FROM AUTHOR]

The increasing demand for rare earth elements (REEs) motivates the development of novel strategies for cost-effective REE recovery from secondary sources, especially rare earth tailings. The biggest challenges in recovering REEs from ion-adsorption rare earth tailings are incomplete extraction of cerium (Ce) and the coleaching of iron (Fe) and manganese (Mn). Here, a synergistic process between reduction and stabilization was proposed by innovatively using elemental sulfur (S) as reductant for converting insoluble CeO 2 into soluble Ce 2 (SO 4 ) 3 and transforming Fe and Mn oxides into inert FeFe 2 O 4 and MnFe 2 O 4 spinel minerals. After the calcination at 400 °C, 97.0% of Ce can be dissolved using a diluted sulfuric acid, along with only 3.67% of Fe and 23.3% of Mn leached out. Thermodynamic analysis reveals that CeO 2 was indirectly reduced by the intermediates MnSO 4 and FeS in the system. Density functional theory calculations indicated that Fe(II) and Mn(II) shared similar outer electron arrangements and coordination environments, favoring Mn(II) over Ce(III) as a replacement for Fe(II) in the FeO 6 octahedral structure of FeFe 2 O 4 . Further investigation on the leaching process suggested that 0.5 mol L -1 H 2 SO 4 is sufficient for the recovery of REEs (97.0%). This research provides a promising strategy to selectively recover REEs from mining tailings or secondary sources via controlling the mineral phase transformation.

Nickel (Ⅱ)-ethylenediaminetetraacetic acid (Ni-EDTA) complexes are widely present in electroplating effluents. Owing to its chemical stability, Ni-EDTA is hardly removed in traditional Fenton/Fenton-like processes with conventional iron (Fe)-based catalyst. In this study, oxygen vacancies were introduced into our highly efficient and novel Fe 3 O 4 @γ-Al 2 O 3 catalysts using Cu doping for Ni-EDTA decomposition in Fenton-like system. Without noble-metal cocatalyst, the introduction of oxygen vacancies in Cu-doped Fe 3 O 4 @γ-Al 2 O 3 catalysts exhibit excellent Fenton-like activity even in neutral or alkaline conditions. Experimental results revealed that, without the aid of extra energy, Ni-EDTA complexes could be effectively decomposed over oxygen vacancies-based catalyst. Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O 2 -TPD), and hydrogen temperature-programmed reduction (H 2 -TPR) were used to get a deep insight into the decomposition mechanism. Additionally, by employing the Al-containing support, stable layered double-hydroxide phases of NiAl could be formed, indicating that a synergy of oxidation and adsorption could simultaneously take place, which led to the recovery of released Ni 2+ ions and also reduction in secondary pollution. To investigate the decomposition process of Ni-EDTA over oxygen vacancies-based catalyst, liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (LC-MS/MS) was employed to identify the generated intermediates, and thus, a plausible decomposition pathway was successfully conceived., (Copyright © 2019 Elsevier Ltd. All rights reserved.)