The recovery of uranium from wastewater and safe treatment of U(VI)-containing wastewater are of great important to ensure the sustainable development of nuclear-related energy. Although abundant ...studies of U(VI) sorption on various adsorbents have been widely achieved, U(VI) sorption at extreme pH and trace concentration is challenging issues due to limited sorption activity of natural adsorbents. The development of novel materials with highly efficient and excellent selectivity for capturing U(VI) from nuclear-related wastewater and seawater is highly desirable. In this study, amidoxime/carbon nitride (AO/g-C3N4) was fabricated and captured U(VI) under a variety of water chemistry. We demonstrated that AO/g-C3N4 exhibited the high adsorption capacities (312 mg/g at pH 6.8), fast removal equilibrium (>98% at 10 min) and superior selectivity for U(VI) compared with the other radionuclides (e.g., 19.76 mg/g of Cs(I)). In addition, AO/g-C3N4 exhibited the high uranium extraction capacity from natural seawater (9.55 mg/g at saturation time of 5.5 days) compared to vanadium (1.85 mg/g). U(VI) adsorption behavior at different pH can be excellently fitted by the surface complexation modeling with three inner sphere surface complexes (i.e., SOUO2(CO3)23−, SO(UO2)3(OH)50 and SOUO2+ species). According to XPS (X-ray Photoelectron Spectroscopy) analysis, the strong complexation of U(VI) with AO groups retained in C3N4 nanosheet. The split of U-Oeq2 subshell and the occurrence of U–C shell further demonstrated inner-sphere surface complexation by EXAFS (X-Ray Absorption Fine Structure) spectra analyses. These results revealed that the high potential of AO/g-C3N4 materials for selective U(VI) capture from wastewater and seawater.
•The amidoxime/carbon nitride was fabricated and captured U(VI) in solution.•AO/g-C3N4 exhibited the high adsorption capacities and superior selectivity.•U(VI) adsorption behavior could be fitted by the surface complexation modeling.•The strong complexation of U(VI) and AO groups retained in C3N4 nanosheet.
Various kind of organics are toxic and detrimental, resulting in eutrophication, black, odorous water and so on. Photocatalysis has been deemed to be a promising technology which can decompose ...different kinds of organic pollutants under visible light irradiation, finally achieving non-poisonous, harmless CO2, water and other inorganic materials. Bismuth oxychloride (BiOCl) is considered as a promising photocatalyst for the efficient degradation of organic pollutants due to its high chemical stability, unique layered structure, resistance to corrosion and favorable photocatalytic property. However, BiOCl can only absorb UV irradiation because of its wide band gap of 3.2 eV–3.5 eV that limits its photocatalytic performance. Herein, a lot of methods have been reviewed to improve its photocatalytic activity. We introduced the unique and special layered structure of BiOCl, the typical and common synthesis methods that can control the morphology, and the most important part is varies of modification routes of BiOCl and the application of BiOCl-based materials for photocatalytic degradation of organic pollutants. Besides, we summarized the crucial issues and perspectives about the application of BiOCl in pollution management.
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•The synthesis methods of BiOCl-based composites are reviewed.•Metal-doping, nonmetal-doping and OVs introduction functions are summarized.•Recent catalytic applications of BiOCl-based photocatalysts are discussed.•The mechanisms of BiOCl-based photocatalysts are analyzed in catalysis.
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.
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•Covalent organic frameworks (COFs) are a new type of crystalline porous materials known for chemical stability, high specific surface area, and orderly porous channels.With the rapid growth of industrialization, water pollutants remain a serious issue of public health and environmental protection•COFs as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants in water is becoming a hot topic•Information about the interaction mechanisms between various pollutants and COFs materials are summarized.The perspectives and challenges are proposed to provide some useful inspiration for the application of COFs in environmental pollution management
The novel biochar supported by starch and nanoscale iron sulfide (SFeS@Biochar) composites were successfully prepared through coupling of biochar derived from peanut shell with nanoscale ferrous ...sulfide and starch under nitrogen atmosphere. It had the advantages of biochar, starch, and nanoscale ferrous sulfide. Therefore, it could overcome some shortcomings. The nanoscale ferrous sulfide particles and starch were thought to be loaded successfully on the surface of the biochar by SEM, EDS, BET, XRD, FT-IR, and XPS techniques. High uptake capacity of U(VI) by SFeS@Biochar could be attributed to reactive reaction of FeS nanoparticles and adsorptive of a lot of functional groups. The proposed reaction mechanisms of the U(VI) uptake by SFeS@Biochar were electrostatic attraction, surface complexation, precipitation, and reductive reaction. It also might be an improved environmentally friendly material for U(VI) removal.
Biochar shows significant potential to serve as a globally applicable material to remediate water and soil owing to the extensive availability of feedstocks and conducive physio-chemical surface ...characteristics. This review aims to highlight biochar production technologies, characteristics of biochar, and the latest advancements in immobilizing and eliminating heavy metal ions and organic pollutants in soil and water. Pyrolysis temperature, heat transfer rate, residence time, and type of feedstock are critical influential parameters. Biochar’s efficacy in managing contaminants relies on the pore size distribution, surface groups, and ion-exchange capacity. The molecular composition and physical architecture of biochar may be crucial when practically applied to water and soil. In general, biochar produced at relatively high pyrolysis temperatures can effectively manage organic pollutants via increasing surface area, hydrophobicity and microporosity. Biochar generated at lower temperatures is deemed to be more suitable for removing polar organic and inorganic pollutants through oxygen-containing functional groups, precipitation and electrostatic attraction. This review also presents the existing obstacles and future research direction related to biochar-based materials in immobilizing organic contaminants and heavy metal ions in effluents and soil.
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Highlights
The synthesis strategies and characteristics of biochar are introduced.
The removal of contaminants from soil and water is explicated emphatically.
The removal behaviors of heavy metal ions and organics are determined.
Mechanisms and influencing factors of pollutant removal by biochar are discussed.
Prospects of biochar-based materials for contaminant removal are proposed.
Effect of phosphate on the reduction of U(VI) on nZVI was determined by batch, XPS, XANES and EXAFS techniques. The batch experiments showed that nZVI was quite effective for the removal of uranium ...under the anaerobic conditions, whereas the addition of phosphate enhanced uranium removal over wide pH range. At low pH, the reduction of U(VI) to U(IV) significantly decreased with increasing phosphate concentration by XPS and XANES analysis. According to EXAFS analysis, the occurrence of UU shell at 10 mg/L phosphate and pH 4.0 was similar to that of U(IV)O2(s), whereas the UP and UFe shells were observed at 50 mg/L phosphate, revealing that reductive co-precipitate (U(IV)O2(s)) and precipitation of uranyl-phosphate were observed at low and high phosphate, respectively. The findings are crucial for the prediction of the effect of phosphate on the speciation and binding of uranium by nZVI at low pH, which is significant in controlling the mobility of U(VI) in contaminated environments.
•Phosphate enhanced uranium removal at pH 2.0–11.0•Decreased reduction of U(VI) significantly was observed at high phosphate.•EXAFS analysis demonstrated that uranium removal at low phosphate was reduction.•Uranium removal at high phosphate was uranyl-phosphate precipitation.
The large amounts ofheavy metal from landscape wastewater have become serious problems of environmental pollution and risks for human health. The development of efficient novel adsorbent is a very ...important for treatment of heavy metal. The functionalized porous nanoscale Fe
3
O
4
particles supported biochar from peanut shell (PS-Fe
3
O
4
) for removal of Pb(II) ions from aqueous solution was investigated. The characterization of PS-Fe
3
O
4
composites showed that biochar was successfully coated with porous nanoscale Fe
3
O
4
particles. The pseudo second-order kinetic model and Langmuir model were more fitted for describing the adsorption process of Pb(II) ions in solution. The adsorption process of Pb(II) ions removal by PS-Fe
3
O
4
composites was a spontaneous and endothermic process. The adsorption mechanisms of Pb(II) ions by PS-Fe
3
O
4
composites were mainly controlled by the chemical adsorption process. The maximum adsorption capacity of Pb(II) ions removal in solution by PS-Fe
3
O
4
composites reached 188.68 mg/g. The removal mechanism included Fe–O coordination reaction, co-precipitation, complexation reaction, and ion exchange. PS-Fe
3
O
4
composites were thought as a low-cost, good regeneration performance, and high efficiency adsorption material for removal of Pb(II) ions in solution.
The interaction of Sr(II) on magnetic polyaniline/graphene oxide (PANI/GO) composites was elucidated by batch, EXAFS, and surface complexation modeling techniques. The batch experiments showed that ...decreased uptake of Sr(II) on magnetic PANI/GO composites was observed with increasing ionic strength at pH <5.0, whereas no effect of ionic strength on Sr(II) uptake was shown at pH >5.0. The maximum uptake capacity of magnetic PANI/GO composites derived from the Langmuir model at pH 3.0 and 293 K was 37.17 mg/g. The outer-sphere surface complexation controlled the uptake of Sr(II) on magnetic PANI/GO composites at pH 3.0 due to the similarity to the EXAFS spectra of Sr2+ in aqueous solutions, but the Sr(II) uptake at pH 7.0 was inner sphere complexation owing to the occurrence of the Sr–C shell. According to the analysis of surface complexation modeling, uptake of Sr(II) on magnetic PANI/GO composites was well simulated using a diffuse layer model with an outer-sphere complex (SOHSr2+ species) and two inner-sphere complexes (i.e., (SO)2Sr(OH)− and SOSr+ species). These findings are crucial for the potential application of magnetic nanomaterials as a promising candidate for the uptake of radionuclides for environmental remediation.
In this study, a novel synergistic photocatalyst (Fe3O4/GO/g-C3N4 composites) were constructed by chemical precipitation of Fe3O4 nanoparticles on surface of GO/g-C3N4 suspension. The ...characterization results indicated that Fe3O4/GO/g-C3N4 composites exhibited high efficient separation of photogenerated electron–hole pair, narrow bandgap (∼2.38 eV) and wide absorption range. The incorporation of Fe3O4 significantly increased the photocatalytic performance of GO/g-C3N4 composites due to synergistic effect. More than 90% of U(VI) was photo-reduced by Fe3O4/GO/g-C3N4 composites within 2 h under visible light irradiation. The trapping experiments and XPS analysis indicated that the photogenerated electrons and superoxide (⋅O2) radicals are responsible for U(VI) removal. These findings indicated that magnetic g-C3N4 composites can be used as excellent candidates for the high efficient removal of U(VI) in actual environmental cleanup.
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