Vitamin C mediates the activation of green tea extract to modify nanozero-valent iron composites: Enhanced transport in heterogeneous porous media and the removal of hexavalent chromium

Cr(VI) removal during cotransport of nano-iron-particles combined with iron sulfides in groundwater: Effects of D. vulgaris and S. putrefaciens

Iron-based materials such as nanoscale zerovalent iron (nZVI) are effective candidates to in situ remediate hexachromium (Cr(VI))-contaminated groundwater. The anaerobic bacteria could influence the remediation efficiency of Cr(VI) during its cotransport with nZVI in porous media. To address this issue, the present study investigated the adsorption and reduction of Cr(VI) during its cotransport with green tea (GT) modified nZVI (nZVI@GT) and iron sulfides (FeS and FeS2) in the presence of D. vulgaris or S. putrefaciens in water-saturated sand columns. Experimental results showed that the nZVI@GT preferred to heteroaggregate with FeS2 rather than FeS, forming nZVI@GT-FeS2 heteroaggregates. Although the presence of D. vulgaris further induced nZVI@GT-FeS2 heteroaggregates to form larger clusters, it pronouncedly improved the dissolution of FeS and FeS2 for more Cr(VI) reduction associated with lower Cr(VI) flux through sand. In contrast, S. putrefaciens could promote the dispersion of the heteroaggregates of nZVI@GT-FeS2 and the homoaggregates of nZVI@GT or FeS by adsorption on the extracellular polymeric substances, leading to the improved transport of Fe-based materials for a much higher Cr(VI) immobilization in sand media. Overall, our study provides the essential perspectives into a chem-biological remediation technique through the synergistic removal of Cr(VI) by nZVI@GT and FeS in contaminated groundwater. ENVIRONMENTAL IMPLICATION: The green-synthesized nano-zero-valent iron particles (nZVI@GT) using plant extracts (or iron sulfides) have been used for in situ remediation of Cr(VI) contaminated groundwater. Nevertheless, the removal of Cr(VI) (including Cr(VI) adsorption and Cr(III) generation) could be influenced by the anaerobic bacteria governing the transport of engineered nanoparticles in groundwater. This study aims to reveal the inherent mechanisms of D. vulgaris and S. putrefaciens governing the cotransport of nZVI@GT combined with FeS (or FeS2) to further influence the Cr(VI) removal in simulated complex groundwater media. Our findings provides a chemical and biological synergistic remediation strategy for nZVI@GT application in Cr(VI)-contaminated groundwater.

Groundwater Cr(VI) contamination and remediation: A review from 1999 to 2022

Hexavalent chromium (Cr(VI)) contamination of groundwater has traditionally been an environmental issue of great concern due to its bioaccumulative and highly toxic nature. This paper presents a review and bibliometric analysis of the literature on the interest area "Cr(VI) in groundwater" published in the Web of Science Core Collection from 1999 to 2022. First, information on 203 actual Cr(VI)-contaminated groundwater sites around the world was summarized, and the basic characteristics of the sources and concentrations of contamination were derived. 68.95% of the sites were due to human causes and 56.43% of these sites had Cr(VI) concentrations in the range of 0-10 mg/L. At groundwater sites with high Cr(VI) contamination due to natural causes, 75.00% of the sites had Cr(VI) concentrations less than 0.2 mg/L. A total of 936 papers on "Cr(VI) in groundwater" were retrieved for bibliometric analysis: interest in research on Cr(VI) in groundwater has grown rapidly in recent years; 59.4% of the papers were published in the field of environmental sciences. A systematic review of the progress of studies on the Cr(VI) removal/remediation based on reduction, adsorption and biological processes is presented. Out of 666 papers on Cr(VI) removal/remediation, 512, 274, and 75 papers dealt with the topics of reduction, adsorption, and bioremediation, respectively. In addition, several studies have demonstrated the potential applicability of natural attenuation in the remediation of Cr(VI)-contaminated groundwater. This paper will help researchers to understand and investigate methodological strategies to remove Cr(VI) from groundwater in a more targeted and effective manner.

Mechanistic insights into manganese oxide impacting the oxidation and transport of Cr(III) immobilized by nano-zero valent charged ion particles in water-saturated porous media

The presence of manganese oxide (MnO2) could influence the stability of green-synthesized nano-zero valent iron (nZVI@GT) associated with trivalent chromium (Cr(III)) after its excess application in the in situ remediation of hexachromium (Cr(VI)) contaminated soil. The research findings revealed that the co-transport of the remaining nZVI@GT with Cr(III) was substantially inhibited by high δ-MnO2 concentrations due to the formation of hetero-aggregates between nZVI@GT and δ-MnO2, resulting in an increased irreversible attachment parameter at second-site in a two-site kinetic attachment model. Simultaneously, the Cr(III) complex immobilized on nZVI@GT could be oxidized leading to high levels of Cr(VI) leaching at high δ-MnO2 concentrations. During this process, Mn(IV) was converted to Mn(III)/Mn(II). Subsequently, leachate containing a partial amount of Cr(VI) preferentially adsorbed onto the nZVI@GT surface, enhancing the dispersion of the nZVI@GT and δ-MnO2 agglomerates. Thereafter, nZVI@GT transportability was enhanced with a decreased second-site attachment parameter and the flow content of dissolved Cr(VI) was increased to double, also increasing the potential risk of Cr(VI) being carried by nZVI@GT to underground water systems. This study provides theoretical support for preserving the long-term stability of nZVI@GT after the in situ remediation of heavy metal-contaminated sites in the presence of δ-MnO2.

Green synthesis of nZVI-modified biochar significantly enhanced the removal of Cr(VI) from aqueous solution

Water contamination by hexavalent chromium (Cr(VI)) seriously jeopardizes human health, which is a pressing environmental concern. Biochar-loaded green-synthesized nZVI, as a green and environmentally friendly material, can efficiently reduce Cr(VI) to Cr(III) while removing Cr(VI) from water. Therefore, in this study, an efficient green-modified biochar material (TP-nZVI/BC) was successfully prepared using tea polyphenol (TP) and sludge biochar (BC) using a low-cost and environmentally friendly green synthesis method. The preparation conditions of TP-nZVI/BC were optimized using response surface methodology (RSM), revealing that the dosage of tea polyphenols plays a crucial role in the removal performance (R2 = 1271.09), followed by reaction time and temperature. The quadratic regression model proved accurate. The optimal preparation conditions are as follows: tea polyphenols (TP) dosage at 48 g/L, reaction temperature at 75 ℃, and a reaction time of 3 h. TP-nZVI/BC removed Cr(VI) from water at a rate 7.6 times greater than BC. The pseudo-second-order kinetic model (R2 = 0.987) accurately describes the adsorption process, suggesting that chemical adsorption predominantly controls the removal process. The adsorption of Cr(VI) by TP-nZVI/BC can be well described by the Langmuir model, and the maximum adsorption capacity reached 105.65 mg/g. FTIR and XPS analyses before and after adsorption demonstrate that nZVI plays a crucial role in the reduction process of Cr(VI), and the synergistic effects of surface adsorption, reduction, and co-precipitation enhance Cr(VI) removal. In summary, using green-modified biochar for Cr(VI) removal is a feasible and promising method with significant potential.

Transport of nZVI/copper synthesized by green tea extract in Cr(IV)-contaminated soil: modeling study and reduced toxicity

In this study, nano-zero-valent iron/copper was synthesized by green tea extracts (GT-nZVI/Cu) and produced a stable suspension than nano-zero-valent iron synthesized by green tea extracts (GT-nZVI) injected into Cr(VI)-containing soil column. The equilibrium 1D-CDE model was successfully used to fit the penetration curves of Fe(tot), Fe(aq), and Fe(0) in order to determine the relevant parameters. The hydrodynamic dispersion coefficient of chromium-contaminated soil was 0.401 cm2·h-1, and the pore flow rate was 0.144 cm·h-1. The stable C/C0 of Fe(tot), Fe(aq), and Fe(0) in the effluent were retarded to 0.39, 0.79, and 0.11, respectively, compared to a ratio of 1 for the concentration of the tracer Cl- in the effluent to the concentration in the influent. Additionally, the 1D-CDE model describes the migration behavior of Cr(VI) with a high R2 (> 0.97). The obtained blocking coefficients declined gradually with increasing concentration of GT-nZVI/Cu suspension and decreasing concentration of Cr(VI). The content of reduced chromium in the soil decreased from 2.986 to 1.121 after remediation, while the content of more stable oxidizable chromium and residual chromium increased from 2.975 and 20.021 to 16.471 and 27.612. The phytotoxicity test showed that mung bean seeds still had a germination rate of 90% (control of 100%), root length of 29.63 mm (control of 35.25 mm), and stem length of 17.9 cm (control of 18.96 cm) after remediation with GT-nZVI/Cu. These indicated that GT-nZVI/Cu was effective in immobilizing Cr(VI) in the soil column and reduced the ecological threat. This study provides an analytical basis and theoretical model for the migration of chromium-contaminated soil in practical application.

Applications and synergistic degradation mechanisms of nZVI-modified biochar for the remediation of organic polluted soil and water: A review

Increasing organic pollution in soil and water has garnered considerable attention in recent years. Nano zero-valent iron-modified biochar (nZVI/BC) has been proven to remediate the contaminated environment effectively due to its abundant active sites and unique reducing properties. This paper provides a comprehensive overview of the application of nZVI/BC in organic polluted environmental remediation and its mechanisms. Firstly, the review introduced primary synthetic methods of nZVI/BC, including in-situ synthesis (carbothermal reduction and green synthesis) and post-modification (liquid-phase reduction and ball milling). Secondly, the application effects of nZVI/BC were discussed in remediating soil and water polluted by antibiotics, pesticides, polycyclic aromatic hydrocarbons (PAHs), and dyes. Thirdly, this review explored the mechanisms of the adsorption and chemical degradation of nZVI/BC, and synergistic degradation mechanisms of nZVI/BC-AOPs and nZVI/BC-Microbial interactions. Fourth, the factors that influence the removal of organic pollutants using nZVI/BC were summarized, encompassing synthesis conditions (raw materials, pyrolysis temperature and aging of nZVI/BC) and external factors (reagent dosage, pH, and coexisting substances). Finally, this review proposed future challenges for the application of nZVI/BC in environmental remediation. This review offers valuable insights for advancing technology in the degradation of organic pollutants using nZVI/BC and promoting its on-site application.

In situ prepared Chlorella vulgaris-supported nanoscale zero-valent iron to remove arsenic (III)

Nanoscale zero-valent iron (nZVI) has a high removal affinity toward arsenic (As). However, the agglomeration of nZVI reduces the removal efficiency of As and, thus, limit its application. In this study, we report an environmentally friendly novel composite of Chlorella vulgaris-supported nanoscale zero-valent iron (abbreviated as CV-nZVI) that exhibits a fast and efficient removal of As(III) from As-contaminated water. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterize and analyze the CV-nZVI. These results indicated that the stabilization effect of C. vulgaris reduced the nZVI agglomeration and enhanced the reactivity of nZVI. The experiments showed a removal efficiency of 99.11% for As(III) at an optimum pH of 7.0. The adsorption kinetics and isotherms followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm with the superior maximum adsorption capacities of 34.11 mg/g for As(III). The FTIR showed that the As(III) was adsorbed on the CV-nZVI surface by complexation reaction, and XPS indicated that oxidation reaction was also involved. After five reuse cycles, the removal efficiency of As(III) by CV-nZVI was 32.93%, suggesting that the CV-nZVI had some reusability and regeneration. Overall, this work provides a practical and highly efficient approach for As remediation in As-contaminated water, and simultaneously resolves the agglomeration problems of nZVI nanoparticles.

Nano-size plastics inhibited Cr(VI) species transformation during facilitated transport of green synthesized nano-iron in the presence of oxyanions

Remediating hexavalent chromium (Cr(VI))-contaminated soils using green synthesized nano-iron (g-nZVI), which merits high reactivity, low cost, and environmental friendliness, has attracted significant attention. However, the broad existence of nano plastics (NPs) could adsorb Cr(VI) and subsequently influence in situ remediation of Cr(VI)-contaminated soil by g-nZVI. To clarify this issue and improve the remediation efficiency, we investigated the co-transport between Cr(VI) and g-nZVI coexisting with sulfonyl-amino-modified nano plastics (SANPs) in water-saturated sand media in the presence of oxyanions (i.e., phosphate and sulfate) at environmentally relevant conditions. This study found that SANPs inhibited the Cr(VI) reduction to Cr(III) (i.e., Cr₂O₃) by g-nZVI, attributed to nZVI-SANPs hetero-aggregates and Cr(VI) adsorption on SANPs. Notably, "nZVI-[SANPs•••Cr(III)]" agglomerate happened via complexation of [-NH₃•••Cr(III)] between Cr(III) from Cr(VI) reduced by g-nZVI and amino group on SANPs. Further, the co-presence of phosphate (stronger adsorption on SANPs than g-nZVI) remarkably suppressed Cr(VI) reduction. Then, it promoted the co-transport of Cr(VI) with nZVI-SANPs hetero-aggregates, which could potentially threaten underground water. Fundamentally, sulfate would instead concentrate on SANPs, hardly impacting the reactions between Cr(VI) and g-nZVI. Overall, our findings provide crucial insights into understanding the Cr(VI) species transformation during co-transport with g-nZVI in ubiquitous complexed soil environments (i.e., containing oxyanions) contaminated by SANPs.

Efficient removal of uranium(VI) from aqueous solution by a novel phosphate-modified biochar supporting zero-valent iron composite

Uranium (U) is an important strategic resource as well as a heavy metal element with both chemical and radiotoxicity. At present, the rapid and efficient removal of uranium from wastewater remains a huge challenge for environmental protection and ecological security. In this paper, phosphate-modified biochar supporting nano zero-valent iron (PBC/nZVI) was triumphantly prepared and fully characterized. The introduction of polyphosphate can greatly increase the specific surface area of biochar pores, and then the zero-valent iron can be evenly distributed on the surface of material, thus leading to excellent removal performance of the PBC/nZVI for U(VI). The theoretical maximum U(VI) removal capacity of PBC/nZVI was up to 967.53 mg/g at pH 5. The results of adsorption kinetics, isotherm, and thermodynamics showed that the adsorption of uranium by PBC/nZVI was a monolayer physical adsorption and endothermic reaction. And the PBC/nZVI has favorable selectivity toward uranium against the interference of coexisting metal ions. Further mechanism studies show that the excellent uranium removal performance of PBC/nZVI is mainly attributed to the synergistic effect of physical adsorption and chemical reduction. This work proves that the PBC/nZVI has a wide application prospect in the field of uranium wastewater treatment.

Green Synthesis of Nano-Zero Valence Iron with Green Tea and It's Implication in Lead Removal

The nano-zero valence iron (nZVI) via green synthesis for heavy metal remediation has attracted many attentions due to its low-cost, environmental-safety, relative reproductivity, and high stability. However, influence of synthesis conditions on the physiochemical properties of nZVI via green tea extracts and the responding suspensibility, which is required for high reactivity, has not been fully elucidated. In this study, we investigated the zeta potentials, sedimentation and lead (Pb²⁺) removal capacity of various nZVIs synthesized using green tea extracts. The results showed that the tea extracts extracted at 80^oC presented an excellent activity, which contributed to the outstanding suspensibility and reaction activity of nZVI synthesized in a volume ratio of 1:1 (tea extraction versus Fe²⁺ solution). Thus, the optimized nZVI was successfully prepared with a Pb²⁺ removal capacity (377.3 mg/g), which was seven times stronger than 50.31 mg/g of traditional chemical synthesized nZVI.

Mechanistic insights into sulfate and phosphate-mediated hexavalent chromium removal by tea polyphenols wrapped nano-zero-valent iron

Nano zero-valent iron via green synthesis (g-nZVI) has great potential in removing toxic hexavalent Cr(VI) from industrial wastewater. Sulfate and phosphate in wastewater can influence Cr(VI) removal by g-nZVI. In this study, the Cr(VI) removal kinetics by different g-nZVI materials were investigated with the existence of sulfate and/or phosphate, and the corresponding mechanisms were first revealed using multiple characterizations, including X-ray absorption near-edge spectra (XANES) and X-ray photoelectron spectroscopy (XPS). The results showed that Cr(OH)₃ was the dominant species initially formed on the surface of g-nZVI particles before transforming to Cr₂O₃ during the reaction of g-nZVI with Cr(VI). Sulfate in wastewater can promote the reduction from Cr(VI) to Cr(OH)₃ by g-nZVI, because sulfate triggers the release of Fe(II) and tea polyphenols (from tea extracts) from the g-nZVI surface due to the corrosion of Fe⁰ core, which is in line with an obvious increase in pseudo-second-order rate constant (k₂) and subtle change in Cr(VI) removal capacity (q_e). However, phosphate impedes the g-nZVI corrosion and inhibits q_e because of the inner-sphere complexation of phosphate onto g-nZVI decreasing the released Fe(II) for Cr₂O₃ production. When sulfate and phosphate coexisted in contaminated water, the inhibition effect of phosphate in Cr(VI) removal by g-nZVI was stronger than the promotion of sulfate. Accordingly, q_e value of g-nZVI declined from 93.4 mg g^-1 to 77.5 mg g^-1, while k₂ remained constant as the molar ratio of phosphate/sulfate increased from 0.1 to 10 in water. This study provides new insights into applying g-nZVI in efficient Cr(VI) removal from contaminated water with enrichment of sulphates and phosphates.

Mechanism for the simultaneous removal of Sb(III) and Sb(V) from mining wastewater by phytosynthesized iron nanoparticles

Since antimony (Sb) is a toxic metalloid cost-effective method for the simultaneous removal of the two major Sb species from mining wastewater has attracted much attention. In this study, phytosynthesized iron nanoparticles (nFe) prepared using a eucalyptus leaf extract were successfully used to simultaneously remove Sb(III) and Sb(V) via an adsorption and oxidation mechanism with removal efficiencies of 100 and 97.7% for Sb(III) and Sb(V), respectively. Advanced analysis using X-ray photoelectron spectroscopy (XPS), ion chromatography-atomic fluorescence spectroscopy (IC-AFS), and electrochemical analysis confirmed that Sb(III) was oxidized to Sb(V) by Fe(III) on the nFe surface while Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) indicated that both Sb(III) and Sb(V) were adsorbed onto nFe. Adsorption of both Sb(III) and Sb(V) best fit the Langmuir adsorption model with R² of 0.999 and 0.989, respectively and both followed pseudo-second-order kinetics with R² of 0.999 and 0.981, respectively. Furthermore, the adsorption rate of Sb(III) was faster than that of Sb(V) due to inner-sphere complex formation, and the Fe-O bonds in the asymmetric tetrahedron structure of Sb(III) were easier to break due to a lower energy barrier (0.863 eV). Consequently, a simultaneous removal mechanism of Sb(III) and Sb(V) was proposed. Finally, nFe was used practically to remove Sb in mining wastewater with a removal efficiency of 93.5%, demonstrating that nFe have significant potential to remove Sb in contaminated mining wastewaters.

Escherichia coli and phosphate interplay mediates transport of nanoscale zero-valent iron synthesized by green tea in water-saturated porous media

Green synthesized nano-zero-valent iron (GT-nZVI) has been considered an excellent material for in-situ soil remediation due to its high stability and environmental benignity. However, sufficient transportability of GT-nZVI downstream towards the contaminated sites, likely affected by the physicochemical properties of soil-groundwater, is required for improved in-situ remediation. Thus, the effect of soil components (i.e., bacteria and phosphate) on GT-nZVI transportability is significant. Hence, we studied the transport of GT-nZVI (Fe0 core wrapped by green tea polyphenols) with the existence of E. coli and phosphate in water-saturated porous sand media in NaCl and CaCl2 solutions at pHs 6.0 and 8.0. Also studied were the stability, surface characteristics, and two-site kinetics attachment modeling (TKAM) with Escherichia coli or/and phosphate. The results showed that phosphate could further enhance GT-nZVI co-transport with E. coli by increasing the negative charge on GT-nZVI at pH 6.0. However, E. coli reduced GT-nZVI mobility at pH 8.0 because the cell-cell interactions could mask the negative charges of pre-deposited GT-nZVI on E. coli, forming the large clusters between GT-nZVI and E. coli. Then, phosphate occurrence diminished E. coli inhibition by detaching GT-nZVI from nZVI-E. coli-phosphate polymers due to the stronger phosphate adsorption on E. coli than GT-nZVI at pH 8.0. Overall, TKAM describes the transport and retention of GT-nZVI adequately under various conditions, indicating the deposition order with k2str value as follows: GT-nZVI alone > with (w.) E. coli > w. phosphate > w. combined E. coli & phosphate at pH 6.0. By contrast, w. phosphate > w. E. coli > w. combined E. coli & phosphate > GT-nZVI alone ensued at pH 8.0. This investigation highlights the transport behavior of GT-nZVI associated with surface property changes in complex environments for effective in-situ remediation.

Removal of Cr(VI) by polyaniline embedded polyvinyl alcohol/sodium alginate beads - Extension from water treatment to soil remediation

Efficient nano-scale chromium (Cr) remediating agents used in the water industry may find their application in soil difficult because of the strong aggregation effect. In this study, a millimeter-sized PANI/PVA/SA composite (PPS) was synthesized by embedding polyaniline (PANI) into polyvinyl alcohol (PVA)/sodium alginate (SA) gel beads. Additionally, the PPS was used to recover hexavalent chromium (Cr(VI)) contaminated water and soil to study the remediation impacts and mechanism. Results showed that the PPS was an irregular sphere with a pore size of 24.24 nm and exhibited strong adsorption capacity (83.1 mg/g) for removing Cr(VI) in water. The Cr(VI) adsorption by PPS could be well described with the pseudo-second-order kinetics and the Redlich-Peterson isotherm model, indicating that the chemical reactions were the controlling step in the Cr(VI) adsorption process. PPS also exhibited excellent physicochemical properties (< 13 mg/L TOC release) and reusability (efficiency of 95.25% after four runs) for Cr(VI) removal. Soil incubation results showed that the 5% PPS (5PPS) treatment could efficiently remove 24.17% of total Cr and 52.47% of Cr(VI) in the contaminated soil after 30 days. Meanwhile, the water-soluble and the leaching Cr contents were decreased by 43.37% and 61.78% in the 5PPS group, respectively. Elemental speciation by XPS revealed that Cr(VI) removal from solution and soil proceeded mainly by electrostatic attraction, reduction, and complexation/chelation. The study implied that PPS could be a useful amendment to remediate both the Cr(VI)-contaminated water and soil.

Scaled-up development of magnetically recyclable Fe3O4/La(OH)3 composite for river water phosphate removal: From bench-scale to pilot-scale study

The use of magnetic lanthanum-based materials for phosphate removal from river water has gained increasing attention. However, challenges to produce and use lanthanum-based materials in large-scale or pilot-scale studies remain. In this work, a kilogram-scale Fe₃O₄/La(OH)₃ magnetically recyclable composite for removing phosphate from river water was developed through a low-temperature precipitation route. The composite was used to remove phosphate from river water at both bench- and pilot-scales. Based on the bench-scale tests, the developed Fe₃O₄/La(OH)₃ composite was found to have excellent magnetic particle separation efficiency (>98%) and a sorption capacity of 11.77 mg/g for phosphate. A 1.0 g/L dosage of the composite in the river water sample was able to selectively reduce the phosphate level from 0.089 to 0.005 mg/L in 60 min over five consecutive adsorption cycles. At the pilot-scale, the Fe₃O₄/La(OH)₃ composite only achieved 36.0% phosphate removal efficiency, which is considerably different from the bench-scale results over an operational time of five months and a total treatment volume of 300 m³. This significantly reduced removal efficiency is mainly attributable to turbidity, suspended solids, and organic matter in the river water and the deteriorated magnetic separation efficiency. This study revealed potential challenges and shed new insights on moving magnetic nanocomposite-based technology from the bench-scale to the pilot-scale, which can inspire new designs for the application of similar technology.

Nano zero valent iron encapsulated in graphene oxide for reducing uranium

Nano zero-valent iron (Fe⁰) has been widely used to remove Uranium (U(VI)). In order to enhance the performance of Fe⁰ toward U(VI) removal, the Fe⁰ was assembled into graphene oxide (GO) sheets via 3-aminopropyl triethoxysilane (APTES) as Fe⁰/APTES-GO composites. The Fe⁰/APTES-GO composites were triumphantly prepared, characterized and analyzed by means of Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) together with Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). SEM and TEM-EDS results manifested that Fe⁰ particles were encapsulated into rolled-up GO, which greatly improved the stability of Fe⁰. Batch experiment showed that only a small amount of Fe²⁺ was leached in the first two leaching cycles of Fe⁰/APTES-GO composites. The removal capacity of Fe⁰/APTES-GO composites was up to 1357.99 mg/g at pH = 4.1 and T = 50 °C, which was mainly attributed to the reducing activity of Fe⁰ and an abundance of functional groups (i.e., -COOH, C-OH and -OH) on the Fe⁰/APTES-GO composites. The electrostatic potential (ESP) from the calculation also supported that U(VI) tended to be reduced at the back side of the GO-Fe⁰ cluster.