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: superior adsorbents for the capture of toxic and radioactive metal ions

Environmental remediation of heavy metal ions by novel-nanomaterials: A review.

Summary Covalent organic frameworks (COFs) are a new type of crystalline porous polymers known for chemical stability, excellent structural regularity, robust framework, and inherent porosity, making them promising materials for capturing various types of pollutants from aqueous solutions. This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants. Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints, including batch experiments, theoretical calculations, and advanced spectroscopy analysis. The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents. Several commonly used strategies to enhance COF-based materials’ adsorption performance and the relationship between structural property and sorption ability are also discussed. Finally, a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.

Orderly Porous Covalent Organic Frameworks-based Materials: Superior Adsorbents for Pollutants Removal from Aqueous Solutions

Boron nitride-based materials for the removal of pollutants from aqueous solutions: a review.

Recent advances in layered double hydroxide-based nanomaterials for the removal of radionuclides from aqueous solution.

As a class of famous carbon materials, biochars (BCs) and their derivative materials with excellent physicochemical properties and diversified functionalities present great potential in wastewater treatment fields. This review focuses on the latest development in reported biochar-based materials as superior adsorbents or catalysts for removing harmful organic contaminants from wastewater. The construction and properties of biochar-based materials are briefly introduced at the beginning. As one of the major factors affecting the properties of BCs, the wide diversity of feedstocks, such as agricultural and forest residues, industrial by-products as well as municipal wastes, endows BCs different chemical compositions and structures. Woody and herbaceous BCs usually have higher carbon contents, larger surface areas and strong aromaticity, which is in favor of the organic contaminant removal. Driven by the desire of more cost-effective materials, several types of biochar-based hybrid materials, such as magnetic BC composites (MBC), nanometal/nanometallic oxides/hydroxide BC composites and layered nanomaterial-coated BCs, as well as physically/chemically activated BCs, have also been developed. With the help of foreign materials, these types of hybrid BCs have excellent capacities to remove a wide range of organic contaminants, including organic dyestuff, phenols and chemical intermediates, as well as pharmaceutically active compounds, from aquatic solutions. Depending on the different types of biochar-based materials, organic contaminants can be removed by different mechanisms, such as physical adsorption, electrostatic interaction, π–π interaction and Fenton process, as well as photocatalytic degradation. In summary, the low cost, tunable surface chemistry and excellent physical–chemical properties of BCs allow it to be a potential material in organic contaminant removal. The combination of BCs with foreign materials endows BCs more functionalities and broader development opportunities. Considering the urgent demand of practical wastewater treatment, we hope more researches will focus on the applications and commercialization of biochar-based materials.

Biochar-based materials and their applications in removal of organic contaminants from wastewater: state-of-the-art review

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 (–CN) 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 –CN 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.

Visible-light-driven activation of persulfate over cyano and hydroxyl group co-modified mesoporous g-C3N4 for boosting bisphenol A degradation

Graphene oxide and Ni-Al layered double hydroxides (GO@LDH) nanocomposites were synthesized via a one-pot hydrothermal process, and characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy in detail. The exploration of U(VI) sorption on GO@LDH surface was performed as a function of ionic strength, solution pH, contact time, U(VI) initial concentrations and temperature. Results of Langmuir isotherms showed that the sorption capacity of GO@LDH (160 mg/g) was much higher than those of LDH (69 mg/g) and GO (92 mg/g). The formed surface complexes between surface oxygen-containing functional groups of GO@LDH and U(VI) turned out to be the interaction mechanism of U(VI) with GO@LDH. According to the thermodynamic studies results, the sorption interaction was actually a spontaneous and endothermic chemical process. The sorption isotherms were better fitted with the Langmuir model compared with other models, which suggested the interaction was mainly dominated by monolayer coverage. The GO@LDH nanocomposites provide potential applications as adsorbents in the enrichment of radionuclides from wastewater in nuclear waste management and environmental remediation.

Shuang Song

Papers

Biochar-based materials and their applications in removal of organic contaminants from wastewater: state-of-the-art review

Visible-light-driven activation of persulfate over cyano and hydroxyl group co-modified mesoporous g-C3N4 for boosting bisphenol A degradation

One-pot synthesis of graphene oxide and Ni-Al layered double hydroxides nanocomposites for the efficient removal of U(VI) from wastewater

A novel multi-shelled Fe3O4@MnOx hollow microspheres for immobilizing U(VI) and Eu(III)

Simultaneous removal of U(VI) and humic acid on defective TiO2−x investigated by batch and spectroscopy techniques