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Photocatalysis and persulfate synergistic catalysis have recently become promising technologies for degrading refractory organic contaminants in effluents. In this work, Fe⁰@Fe₃O₄ is successfully immobilized on a N-deficient g-C₃N₄/diatomite composite (NGD) via a simple self-assembly process. The structural characteristics and peroxymonosulfate activation ability of the composite under visible-light irradiation are explored in detail. Notably, the introduction of NGD affects the crystallinity and morphology of Fe⁰@Fe₃O₄, forming homogenously distributed nanoparticles rather than irregular and agglomerated crystals with rod-like structures. The synthesized Fe⁰@Fe₃O₄/N-deficient g-C₃N₄/diatomite composite (FNGD) exhibits a superior removal percentage of bisphenol A (> 95% within 15 min). Furthermore, its degradation rate constant (k) is ~59 and ~27 times higher than those of NGD and bare Fe⁰@Fe₃O₄, respectively. Moreover, holes (h_vb⁺), singlet oxygen (¹O₂) and superoxide free radicals (^•O₂^-) play a major role in the FNGD/peroxymonosulfate/visible system based on radial quenching experiments and electron paramagnetic resonance spectra. Overall, this study provides novel insights into visible light-assisted peroxymonosulfate activation by the g-C₃N₄/mineral-based composite for wastewater treatment. LESS      Full article

The recovery of rare earth elements (REEs) from the Western Kentucky No. 13 and Fire Clay coal wastes was enhanced by alkali pretreatment with concentrated NaOH solutions. The enhancements in the recovery of light REEs (LREEs) are more significant than those of heavy REEs (HREEs). For example, after treating with 5 M NaOH at 90 °C, the recovery of LREEs from the Western Kentucky No. 13 coal waste increased from 26% to 71%, while the recovery of HREEs only increased from 29% to 41%. Based on mineralogical studies through scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray diffraction analyses, two mechanisms were proposed to explain the positive effect of alkali pretreatment: (1) decomposition of rare earth minerals (primarily crandallite-group minerals) during the alkali pretreatment, and (2) liberation of encapsulated REE-bearing particles due to the enhanced dissolution of clay minerals. The more significant enhancements in the recovery of LREEs were explained by the fact that the REEs comprised in the crandallite-group minerals were mainly LREEs. Compared with zircon, monazite, and xenotime, alkali pretreatment with 5 M NaOH led to a more significant decomposition of crandallite-group minerals. In order to further increase the recovery of REEs, particularly HREEs, harsher alkali treatment conditions are required. LESS      Full article

In this work, iminodiacetic acid-functionalized graphene oxide (IDA@GO) is prepared and used as a nanocollector for enhancing and selectively recovering Pb(II) from a strongly acidic waste electrolyte via ion flotation. IDA@GO is characterized by Fourier transform infrared spectroscopy, zeta potential measurements and atomic force microscopy. The effects of pH, reaction time, cetyl trimethyl ammonium bromide (CTAB) dosage and aeration rate on the Pb(II) concentration and turbidity of the residual solution are examined systematically. The experimental results show that the adsorption capacity of Pb(II) on IDA@GO can reach 91.21 mg/g at pH 2. After froth flotation, the turbidity of the treated solution decreased to 0.55 NTU under the optimal CTAB dosage and aeration rate. In addition, as compared with GO, the relative selectivity coefficients of IDA@GO are up to 1.304, 1.471, 1.807 and 1.509 for Co(II), Ni(II), Zn(II) and Cd(II), respectively, thereby exhibiting better selectivity performance. Moreover, IDA@GO can be reused as a nanocollector in ion flotation and exhibits ideal regeneration performance. In addition, the recovery mechanism is found to proceed through Pb(II) adsorbing on IDA@GO by electrostatic attraction, ion exchange and surface complexation, with the addition of CTAB improving the hydrophobicity of Pb(II)-loaded IDA@GO flocs, thus achieving the recovery of Pb(II) via froth flotation. LESS      Full article

Molybdenite (MoS₂) has been widely used in the fields of catalysis, desalination, energy storage and conversion and optoelectronics as a result of its unique crystal structures and unusual properties. In the last decade, the modification of the surface, structural and semiconducting properties of zero-, two- and three-dimensional (0D, 2D and 3D) MoS₂ for enhanced applications has attracted considerable attention. In this review, we summarize the synthesis, modification methods and application of 0D, 2D and 3D MoS₂. The unique structures and properties of 0D, 2D and 3D MoS₂ are first introduced. Next, the preparation methods of 0D, 2D and 3D MoS₂ are summarized. The modification methods, including surface, structural and composite engineering, for enhancing the physical and chemical properties of 0D, 2D and 3D are also discussed. Finally, inspired by natural and modified MoS₂, future suggestions for the design of novel 0D, 2D and 3D MoS₂ for various applications are also suggested. This review offers new insights into the design and construction of novel and efficient 0D, 2D and 3D MoS₂ for practical applications. LESS      Full article

Action is currently being taken globally to mitigate global warming.The objective of reducing CO₂ emissions is not a burden for society but is a significant opportunity for evolution in various industries for the sustainable production of energy and the essential minerals, metals, and materials required for modern society. CO₂ mineralization is one of the most promising methods to effectively reduce CO₂ emissions via the formation of stable mineral carbonates. Accelerated mineral carbonation requires high capital costs for implementation. Accordingly, it has thus far not been economically feasible to carry out accelerated CO₂ mineralization alone. Accelerated CO₂ mineralization must be combined with other associated technologies to produce high-value products. The technical developments in enhanced metal recovery, nanomaterials, enhanced flotation, H₂ production and applications in the cement industry may be suitable options. The utilization and generation of valuable byproducts may determine the economic feasibility of CO₂ mineralization processes. The need for CO₂ reduction and utilization can contribute to driving the development of many innovative and sustainable technologies for the future benefit of society. The implementation of carbon taxation may also significantly motivate the development of these technologies and their potential application. LESS      Full article