Highly efficient removal of metal ion pollutants, such as toxic and nuclear waste-related metal ions, remains a serious task from the biological and environmental standpoint because of their harmful ...effects on human health and the environment. Recently, highly porous metal-organic frameworks (MOFs), with excellent chemical stability and abundant functional groups, have represented a new addition to the area of capturing various types of hazardous metal ion pollutants. This review focuses on recent progress in reported MOFs and MOF-based composites as superior adsorbents for the efficient removal of toxic and nuclear waste-related metal ions. Aspects related to the interaction mechanisms between metal ions and MOF-based materials are systematically summarized, including macroscopic batch experiments, microscopic spectroscopy analysis, and theoretical calculations. The adsorption properties of various MOF-based materials are assessed and compared with those of other widely used adsorbents. Finally, we propose our personal insights into future research opportunities and challenges in the hope of stimulating more researchers to engage in this new field of MOF-based materials for environmental pollution management.
Metal-organic framework-based materials represent a new addition to the area of capturing diverse toxic and radioactive metal ions.
Water pollutant treatment has become a critical issue in environmental engineering and protection. Adsorption techniques
via
solid adsorbents have been widely applied for the efficient removal of ...metal ions from wastewater solutions, where polymer-based composites have attracted much attention due to their intrinsic environmentally harmless and degradable properties. Particularly, polymer-based nanocomposites often present superior physical, chemical and mechanical properties, as well as superior compatibility, as compared with single polymers, by incorporating the advantages of both counterparts in the composites. This article is an overview of the versatile polymer-based composites containing different functional organic and/or inorganic counterparts for the removal of hazardous metal ions from wastewater. The synthesis of the adsorbents, adsorption process features and mechanism investigation are highlighted and discussed in detail. The future perspectives and trends in this field are also outlined. We hope that this review will provide some inspiring information for designing and fabricating polymer-based nanocomposites for the removal of diverse heavy metal ions from aqueous solution, and pollution management in the near future.
A review of versatile polymer-based composites containing different functional organic and/or inorganic counterparts for the removal of hazardous metal ions from wastewater solutions.
Through a facile and effective strategy by employing lithium molten salts the controlled synthesis of 2H‐ and 1T‐MoS2 monolayers with high‐yield production is achieved. Both phases of MoS2 monolayers ...exhibit high stabilities. When used as a catalyst for hydrogen evolution, these phased MoS2 monolayers deliver respective advantages in the field of electro‐ and photo‐catalytic hydrogen evolution.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Graphene has attracted multidisciplinary study because of its unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using the modified ...Hummers method, and were used as sorbents for the removal of Cd(II) and Co(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength, and humic acid on Cd(II) and Co(II) sorption were investigated. The results indicated that Cd(II) and Co(II) sorption on graphene oxide nanosheets was strongly dependent on pH and weakly dependent on ionic strength. The abundant oxygen-containing functional groups on the surfaces of graphene oxide nanosheets played an important role on Cd(II) and Co(II) sorption. The presence of humic acid reduced Cd(II) and Co(II) sorption on graphene oxide nanosheets at pH < 8. The maximum sorption capacities (C smax) of Cd(II) and Co(II) on graphene oxide nanosheets at pH 6.0 ± 0.1 and T = 303 K were about 106.3 and 68.2 mg/g, respectively, higher than any currently reported. The thermodynamic parameters calculated from temperature-dependent sorption isotherms suggested that Cd(II) and Co(II) sorptions on graphene oxide nanosheets were endothermic and spontaneous processes. The graphene oxide nanosheets may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.
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IJS, KILJ, NUK, PNG, UL, UM
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•Photodegradation of POPs by GR-based composites was comprehensively reviewed.•Recent developments in the synthesis of GR-based photocatalysts were summarized.•Catalytic mechanisms ...and roles of GR species in composites were elucidated in depth.•Challenges and future research needs in this field were insightfully suggested.
Over the last decade, two-dimensional graphene (2D GR) has brought new impetus in environmental photocatalysis, mainly benefiting from their unique physicochemical and photoelectric structural properties. Numbers of researchers have spared no effort to utilize visible-light-induced GR-based composites as catalyst platform to generate reactive species in photocatalytic oxidation technology. Herein, a comprehensive overview is presented on recent achievements of the construction and water-related applications of these photocatalysts for persistent organic pollutants (POPs) removal. A brief introduction of synthesis strategies is introduced for GR and its derivatives. Roles of GR as supports, flexible substrates and co-catalysts in composites are specifically pointed out with experimental studies. Most importantly, shortcomings (e.g., fast carrier recombination and serious photocorrosion) appeared in visible light photocatalysis and relative solutions by using GR species are clearly investigated. Based on the current research status, special attention has been paid to their promising applications on removing typical POPs, such as phenols, antibiotics, pharmaceuticals and dyes. Also, challenges (e.g., biotoxicity) and prospects are discussed for future developments in this field. This paper enriches the knowledge to deeply understand the catalytic performances and mechanisms of GR-based photocatalysts, and bring better perspectives for researchers in this field.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
► The sulfonated graphene nanosheets were prepared and had high dispersion property in aqueous solution. ► The kinetic and thermodynamic adsorption of 1-naphthol on the sulfonated graphene nanosheets ...was studied. ► The sulfonated graphene nanosheets have the highest adsorption capacity of todays’ nanomaterials.
The sulfonated graphene nanosheets were prepared from graphene oxides. The kinetic and thermodynamic adsorption of 1-naphthol from aqueous solution on the sulfonated graphene nanosheets were investigated under ambient conditions. The results of 1-naphthol kinetic adsorption on sulfonated graphene indicated that the adsorption was inclined to stack on the surface of graphene nanosheets with low activation energy. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption was a spontaneous and endothermic process, and the adsorption was in good agreement with the theory of non-bonding interaction intensity. The adsorption capacities of 1-naphthol on sulfonated graphene nanosheets are ∼2.3
mmol/g at 293.15
K, and ∼6.4
mmol/g at 313.15 and 333.15
K, which are the highest adsorption capacity of todays’ nanomaterials. The results suggest that the sulfonated graphene nanosheets may be a promising suitable candidate for the preconcentration of 1-naphthol from large volume of aqueous solutions in real work in near future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A kind of sulfonated graphene (around 3 nm thick) with high dispersion properties has been synthesized. It is demonstrated to adsorb persistent organic aromatic pollutants effectively from aqueous ...solutions. The adsorption capability of the prepared sulfonated graphene nanomaterials approaches ∼2.3–2.4 mmol g−1 for naphthalene and 1‐naphthol, which is one of the highest capabilities of today's nanomaterials. This highly effective adsorbent may be a promising candidate to remove aromatic chemicals from large volumes of aqueous solutions. It opens a new door for cost effective environmental pollution management with graphene in the near future.
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In this work, structure-deficient mesoporous g-C3N4 (DMCN) was fabricated via a facile hard template approach with water-bath aging pretreatment. The in situ introduced cyano groups (–C≡N) and ...hydroxyl groups (–OH) effectively modulated the energy levels, improved visible light absorption, and meanwhile served as strong electron-withdrawing groups, promoting the efficient separation and transfer of photogenerated charge carriers. With the addition of persulfate (PS) as an oxidant, DMCN exhibited superior catalytic activity and stability for bisphenol A (BPA) degradation. 100% BPA could be degraded for optimal DMCN-3.5 with 0.5 g L−1 catalyst and 1.0 g L−1 PS under visible light (420 nm ≤ λ ≤ 780 nm) within 15 min, whose reaction rate (0.317 min−1) was ∼39.6 times higher than that of bulk g-C3N4 (0.008 min−1). Based on EPR and quenching tests, h+ and SO4·− radicals were determined as major oxidizing species in the DMCN/PS/Vis system. The enhanced catalytic performance was mainly attributed to PS serving as the electron acceptor and transfer of photogenerated e− to PS via –C≡N and C–OH groups, resulting in the efficient activation of PS for SO4·− and a high light quantum efficiency. This work gives novel insights into in situ defect engineering for g-C3N4 and offers a new chance for visible-light-induced sulfate radical-based Fenton-like system to govern contaminated water.
Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and ...photoreduce CO2 with high efficiency under visible‐light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long‐lived electrons for the reduction of CO2 molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO2, which is equivalent to a 3.13‐fold improvement in CO evolution rate (200.6 μmol g−1 h−1) and a 5.93‐fold enhancement in CH4 generation rate (36.67 μmol g−1 h−1) compared to the parent MOF.
Less is more: A photocatalyst comprising atomically dispersed Co in an extended MOF efficiently reduces CO2. Directional migration of photogenerated excitons from porphyrin to catalytic cobalt centers was witnessed, thereby supplying long‐lived electrons for reduction of CO2 molecules adsorbed on cobalt centers.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Graphitic carbon nitride (g‐C3N4) has recently emerged as an attractive photocatalyst for solar energy conversion. However, the photocatalytic activities of g‐C3N4 remain moderate because of the ...insufficient solar‐light absorption and the fast electron–hole recombination. Here, defect‐modified g‐C3N4 (DCN) photocatalysts, which are easily prepared under mild conditions and show much extended light absorption with band gaps decreased from 2.75 to 2.00 eV, are reported. More importantly, cyano terminal CN groups, acting as electron acceptors, are introduced into the DCN sheet edge, which endows the DCN with both n‐ and p‐type conductivities, consequently giving rise to the generation of p–n homojunctions. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation, and results in a fivefold enhanced photocatalytic H2 evolution activity. The findings deepen the understanding on the defect‐related issues of g‐C3N4‐based materials. Additionally, the ability to build homojunction structures by the defect‐induced self‐functionalization presents a promising strategy to realize precise band engineering of g‐C3N4 and related polymer semiconductors for more efficient solar energy conversion applications.
The p–n homojunction graphitic carbon nitride (g‐C3N4) photocatalysts with extended light absorption are prepared via in situ bond modulation, which is achieved by low‐temperature heating g‐C3N4 with NaBH4. Such a p–n homojunction endows g‐C3N4 with much increased π‐electron delocalization and highly improved carrier separation and transfer. Consequently, the materials exhibit a fivefold enhanced photocatalytic hydrogen evolution activity under visible light irradiation.
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