Oxygen-Content-Controllable Graphene Oxide from Electron-Beam-Irradiated Graphite: Synthesis, Characterization, and Removal of Aqueous Lead [Pb(II)]

Construction of a MIL-101-DGA (MOF) Coupling Betaine Hydrochloride System for the Green and Efficient Separation of Zirconium and Hafnium

Metal-organic framework materials (MOFs) have potential for practical applications in solid-phase separation technology. However, no studies of the separation of hafnium and zirconium using MOFs have been performed. This work synthesized MIL-101-DGA solid-phase adsorbent material, which was synthesized using amino-containing MIL-101-NH2 as a matrix material by introducing diglycolic acid (DGA) functional groups through a one-step ring-opening reaction. Betaine hydrochloride was selected as the complexing agent to establish the MIL-101-DGA coupling betaine hydrochloride push-pull system; this system could act as an alternative to the traditional MIBK-HSCN separation system. We are the first to report that this MIL-101-DGA coupling betaine hydrochloride system could obtain separation coefficients (βZr/Hf) of 19.7 at pH 0.50 and 8.2 at pH 1.46. Furthermore, the highest adsorption capacity of MIL-101-DGA for Zr was 63.7 mg/g. These results demonstrated that MIL-101-DGA had excellent separation performance for zirconium and hafnium in the betaine hydrochloride medium. This system also exhibited an outstanding cycling performance and immersion stability. After multiple adsorption/desorption cycles and 1 week of immersion in various solutions, the structure and adsorption capability essentially remained unchanged. The adsorption mechanism was thoroughly examined using a suite of analysis and detection methods, including the slope method, FT-IR, XPS, and DFT. In conclusion, we propose that the MIL-101-DGA coupling betaine hydrochloride system, which is an efficient and green separation system, could replace the traditional MIBK-HSCN separation system; our study provides a concept for the industrialization of zirconium and hafnium separation from key mineral resources.

Vitamin B12 and iron-rich sludge-derived biochar enhanced PFOA biodegradation: Importance of direct inter-species electron transfer and functional microbes

Owing to the strong C-F bond in nature and the rigidity of the poly-fluoroalkyl chain, perfluorooctanoic acid (PFOA) is difficult to be eliminated by reactive species and microbes in environments, thus posing a serious threat to ecosystems. Vitamin B12 as a cofactor for enzymes, and biochar as the electron providers and conductors, were integrated to enhance PFOA biodegradation. The raw material of biochar was the sludge after dewatering by adding 50 mg/g DS of Fe(III). After pyrolysis under high temperature (800 °C), biochar (SC800) detected high content of Fe(II) (197.64 mg/g) and abundant oxygen-containing functional groups, thus boosting PFOA biodegradation via donating electrons. 99.9% of PFOA could be removed within 60 d as 0.1 g/L SC800 was presented in the microbial systems containing vitamin B12. Moreover, vitamin B12 facilitated the evolution of Sporomusa which behaved the deflorination. Via providing reactive sites and mediating direct inter-species electron transfer (DIET), SC800 boosted PFOA biodegradation. Corresponding novel results in the present study could guide the development of bioremediation technologies for PFOA-polluted sites.

Graphene oxide worsens copper-mediated embryo-larval toxicity in the pacific oyster while reduced graphene oxide mitigates the effects

Due to their properties, graphene-based nanomaterials (GBMs) are triggering a great interest leading to an increase of their global production and use in new applications. As a consequence, their release into the environment is expected to increase in the next years. When considering the current knowledge in the evaluation of GBMs ecotoxic potential, studies aiming to evaluate the hazard associated to these nanomaterials towards marine species and particularly considering potential interactions with other environmental pollutants such as metals are scarce. Here we evaluated the embryotoxic potential of GBMs, which include graphene oxide (GO) and its reduced form (rGO), both individually and in combination with copper (Cu) as a referent toxicant, towards early life stages of the Pacific oyster through the use of a standardized method (NF ISO 17244). We found that following exposure to Cu, dose-dependent decrease in the proportion of normal larvae was recorded with an Effective Concentration leading to the occurrence of 50% of abnormal larvae (EC₅₀) of 13.85 ± 1.21 μg/L. Interestingly, the presence of GO at a non-toxic dose of 0.1 mg/L decreased the Cu EC₅₀ to 12.04 ± 0.85 μg/L while it increased to 15.91 ± 1.57 μg/L in presence of rGO. Based on the measurement of copper adsorption, the obtained results suggest that GO enhances Cu bioavailability, potentially modifying its toxic pathways, while rGO mitigates Cu toxicity by decreasing its bioavailability. This research underscores the need to characterize the risk associated to GBMs interactions with other aquatic contaminants and supports the adoption of a safer-by-design strategy using rGO in marine environments. This would contribute to minimize the potential adverse effects on aquatic species and to reduce the risk for economic activities associated to coastal environments.

Recovery, regeneration and sustainable management of spent adsorbents from wastewater treatment streams: A review

Adsorption is the most widely adopted, effective, and reliable treatment process for the removal of inorganic and organic contaminants from wastewater. One of the major issues with the adsorption-treatment process for the removal of contaminants from wastewater streams is the recovery and sustainable management of spent adsorbents. This review focuses on the effectiveness of emerging adsorbents and how the spent adsorbents could be recovered, regenerated, and further managed through reuse or safe disposal. The critical analysis of both conventional and emerging adsorbents on organic and inorganic contaminants in wastewater systems are evaluated. The various recovery and regeneration techniques of spent adsorbents including magnetic separation, filtration, thermal desorption and decomposition, chemical desorption, supercritical fluid desorption, advanced oxidation process and microbial assisted adsorbent regeneration are discussed in detail. The current challenges for the recovery and regeneration of adsorbents and the methodologies used for solving those problems are covered. The spent adsorbents are managed through regeneration for reuse (such as soil amendment, capacitor, catalyst/catalyst support) or safe disposal involving incineration and landfilling. Sustainable management of spent adsorbents, including processes involved in the recovery and regeneration of adsorbents for reuse, is examined in the context of resource recovery and circular economy. Finally, the review ends with the current drawbacks in the recovery and management of the spent adsorbents and the future directions for the economic and environmental feasibility of the system for industrial-scale application.

Ball-milled magnetite for efficient arsenic decontamination: Insights into oxidation-adsorption mechanism

Conventional adsorbents for decontaminating arsenic exhibit low efficacy for the removal of arsenite (As(III)). This study aims to develop a robust As adsorbent from natural magnetite (M₀) via a facile ball milling process, and evaluate their performance for decontaminating As(III) and As(V) in water and soil systems. The ball milling process decreased the particle size and crystallinity of M₀, resulting in pronounced As removal by the ball-milled magnetite (M_m). Ball milling under air facilitated the formation of Fe-OH and Fe-COOH functional groups on M_m interface, contributing to effective elimination of As(III) and As(V) via hydrogen bonding and complexation mechanisms. Synergistic oxidation effects of hydroxyl and carboxyl groups, and reactive oxygen species (O₂^·-, and ·OH) on the transformation of As(III) to As(V) during the adsorption were proposed to explain the enhanced As(III) removal by M_m. A short-term soil incubation experiment indicated that the addition of M_m (10 wt%) induced a decrease in the concentration of exchangeable As by 30.25%, and facilitated the transformation of water-soluble As into residual fraction. Ball milling thus is considered as an eco-friendly (chemical-free) and inexpensive (scalable, one-stage process) method for upgrading the performance of natural magnetite towards remediating As, particularly for tackling the highly mobile As(III).

High-performance TFNC membrane with adsorption assisted for removal of Pb(II) and other contaminants

Rapid and thorough removal of heavy metal ions in wastewater is critical for the urgent need of clean water. Herein, we prepared a high-performance thin film nanofibrous composite (TFNC) membrane consisting of a polyacrylonitrile (PAN)-UiO-66-(COOH)₂ composite nanofibrous substrate (CPAN) and a calcium alginate (CaAlg) skin layer. Owing to abundant adsorption sites of UiO-66-(COOH)₂ MOF, the optimal CPAN-2 nanofibrous substrate showed excellent adsorption capacity for lead ions. The maximum Pb²⁺ adsorption capacity of CPAN-2 substrate calculated by Langmuir isotherm model was 254.5 mg/g. Meanwhile, due to the relatively loose structure of CaAlg skin layer, this TFNC membrane showed high water permeate flux about 50 L m^-2h^-1 at 0.1 MPa, and the rejection for dyes was higher than 95%. Therefore, CaAlg/CPAN TFNC membranes were appropriate for dynamic adsorption/filtration to remove Pb²⁺. Compared with original CaAlg/PAN membrane, the optimal CaAlg/CPAN TFNC membrane showed much better ability to treat Pb(II)-containing wastewater and had good recyclability. Most importantly, the CaAlg/CPAN TFNC membrane could treat 7659 L m^-2 wastewater containing single lead ions under WHO drinking water standard, and effectively deal with more simulated lead-containing wastewater. This work could provide a substitutable solution for effective removal of heavy metal ions and other various contaminants in wastewater.

Reduce and concentrate graphene quantum dot size via scissors: vacancy, pentagon-heptagon and interstitial defects in graphite by gamma rays

Graphene quantum dots (GQDs) with ultrafine particle size and centralized distribution have advantages of small size, narrow size distribution and large specific surface area, which make it be better applied in bioimaging, drug delivery and so on. In our research, we used graphite irradiated byγ-rays to successfully prepare GQDs with ultrafine particle size, narrow size distribution and high quantum yields through solvothermal method. Vacancy defects, pentagon-heptagon defects and interstitial defects were introduced to graphite structure after irradiation, which caused the abundance and concentrated distribution of defects. The defects generated by irradiation could damage the lattice structure of graphite to make it easy for introduction of C-O-C inside graphite sheets. The oxygen-containing functional groups in graphene oxide (GO) increased and centrally distributed after irradiation in graphite, especially for C-O-C group, which were beneficial for cutting of GO and grafting of functional groups in GQDs. Therefore, average size of GQDs was successfully reduced to 1.43 nm and concentrated to 0.6-2.4 nm. After irradiation in graphite, the content of carbonyl and C-N in GQDs had a promotion, which suppressed non-radiative recombination and upgraded the quantum yields to 13.9%.

Increased structural defects of graphene oxide compromised reductive capacity of ZVI towards hexavalent chromium

Graphene oxide (GO) was treated with irradiation beams to understand the defective degree of carbon structure of GO in relation to electron transfer property of impregnated zerovalent iron (ZVI). The GO-supported ZVI (ZVI/GO) was synthesized and then characterized by an X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The results showed that the oxygen-bearing functional groups, oxygen content and structural disorder were increased as a function of irradiation beam intensity. ZVI was dominant in the composites, but proportion of iron oxide increased with greater oxygen content. Batch sorption revealed that Cr(VI) removal decreased from 20.11 g kg^-1 to 2.30 g kg^-1 as solution pH rose from 3 to 9. Cr(VI) removal capacity was 26.39 g kg^-1, 23.12 g kg^-1 and 12.35 g kg^-1 for ZVI/GO₀, ZVI/GO_12.3 and ZVI/GO_36.9, respectively. The reduction capacity of sorbents followed similar trends as Cr(VI) sorption as per desorption experiment, which accounted for a major Cr(VI) detoxification mechanism by ZVI/GO composites. The electrochemical tests demonstrated that unfavorable electron transfer rate of ZVI/GO composites was aggravated by greater structural disorder of GO. Thus, higher dose of irradiations could create more disorder in graphitic carbon and promote oxidation of ZVI, which hindered Cr(VI) reduction.

Carbothermal synthesis of biochar-supported metallic silver for enhanced photocatalytic removal of methylene blue and antimicrobial efficacy

Pinewood biochar (PBC)-supported metallic silver (Ag^o) was prepared via a one-step carbothermal reduction route (AgH) or a wet-chemistry reduction method (AgW). XRD and SEM confirmed Ag^o was soldered on PBC matrix. Low methylene blue (MB) sorption was observed for unsupported Ag^o nanoparticles (AgNP), AgH and AgW. Under ultraviolet (UV) light irradiation, net MB degradation by AgH (15.88 g kg^-1) was higher than that of AgW (12.50 g kg^-1) and AgNP (10.27 g kg^-1). TOC removal percentages after degradation corresponded largely to reduction of MB concentrations in solution, indicating MB was dominantly mineralized. Electron paramagnetic resonance (EPR) revealed that MB was degraded by reactive oxygen species (ROS) such as hydroxyl radical (OH), superoxide radical (O₂-) and singlet oxygen (¹O₂). The scavenging experiments further suggested that OH scavengers suppressed MB degradation to a greater extent than other quenchers. Compared to AgW, AgH possessed greater abundance of persistent free radicals, which enhance ROS generation. PBC could also improve separation of electron-hole (e^--h⁺) pairs and enhance electron transfer ascribing to favorable carbon structure. Besides, PBC-Ag^o maintained good antimicrobial efficacy over E.coli DH5α. This work presented a facile carbothermal route to prepare Ag^o-based photocatalysts for dye removal and microbial inhibition in industrial wastewater.

Embryotoxicity assessment and efficient removal of naphthalene from water by irradiated graphene aerogels

Naphthalene has remained a challenge how to eradicate it from the water because of its carcinogenic risk to humans. In the present study, naphthalene prominently increased the rates of embryonic mortality and malformation, and decreased the hatchability of zebrafish which have a high developmental similarity to humans. Moreover, multiple-organ toxicity were notably found in naphthalene-treated zebrafish. Here, irradiated graphene aerogel (IGA) was successfully prepared from high-energy electron beam to generate more wrinkles, folds, defects and a strong absorption capability for naphthalene, compared with the non-irradiated graphene aerogel. IGA was outstandingly found to remove naphthalene from the embryo culture medium, and subsequently inhibit the embryotoxicity and maintain tissue integrity by restoring cardiac function, attenuating apoptosis signals, recovering eye morphology and structure, reducing expression of heat shock protein 70 in the tissues and promoting behavioral capacity. Meanwhile, no obvious negative impact of IGA was found in the developing zebrafish from embryo to larvae. Consequently, reduction in the toxicity of naphthalene during zebrafish embryogenesis was mediated by IGA as an advanced strategy.

Co-transport of Pb(II) and oxygen-content-controllable graphene oxide from electron-beam-irradiated graphite in saturated porous media

It is essential to investigate the role of the surface oxygen content of graphene oxide (GO) in transport processes. In this study, GO was prepared using flake graphite with different radiation doses. The effects of the flow rate and ionic strength (IS) on the migration and co-transport of GO and Pb(II) ions were investigated via laboratory packed-column experiments. The experimental results showed that the mobility of GO in saturated porous media decreased with increasing flow rate. Further, the mobility of GO with a radiation dose of 18 kGy was lower than that of GOs with other radiation doses for an IS below 0.01 M. Regarding the co-transport of irradiated GO and Pb(II) in porous media, the greater the radiation dose, the stronger was the ability of GO to promote Pb(II) transport. The surface oxygen content promoted the ability of GO to remove Pb(II). However, radiation doses exceeding a certain range inhibited the release of Pb(II). The transport of GO in saturated porous media was successfully simulated with the advection-dispersion-reaction (ADR) equation. This study is expected to provide a new perspective on the potential risks of GO due to surface changes during its transport in the environment.

Graphene Composites for Lead Ions Removal from Aqueous Solutions

The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed.

Surface functional groups of carbon-based adsorbents and their roles in the removal of heavy metals from aqueous solutions: A critical review

Carbon-based adsorbents such as graphene and its derivatives, carbon nanotubes, activated carbon, and biochar are often used to remove heavy metals from aqueous solutions. One of the important aspects of effective carbon adsorbents for heavy metals is their tunable surface functional groups. To promote the applications of functionalized carbon adsorbents in heavy metal removal, a systematic documentation of their syntheses and interactions with metals in aqueous solution is crucial. This work provides a comprehensive review of recent research on various carbon adsorbents in terms of their surface functional groups and the associated removal behaviors and performances to heavy metals in aqueous solutions. The governing removal mechanisms of carbon adsorbents to aqueous heavy metals are first outlined with a special focus on the roles of surface functional groups. It then summarizes and categorizes various synthesis methods that are commonly used to introduce heteroatoms, primarily oxygen, nitrogen, and sulfur, onto carbon surfaces for enhanced surface functionalities and sorptive properties to heavy metals in aqueous solutions. After that, the effects of various functional groups on adsorption behaviors of heavy metals onto the functionalized carbon adsorbents are elucidated. A perspective of future work on functional carbon adsorbents for heavy metal removal as well as other potential applications is also presented at the end.

Controllable reduction of graphene oxide by electron-beam irradiation

The oxygen content of graphene oxide (GO) is directly related to its physical and chemical properties, such as hydrophilicity, suspension stability, adsorption, and ion-sieving ability of GO membranes. Here, a series of reduced GO (rGO) with C/O atomic ratios from 1.6 to 4.8 were prepared conveniently by electron-beam irradiation (EBI) with irradiation-dose control. Moreover, a single oxygen-containing group, i.e., epoxy or carbonyl, could be retained mainly in the rGO. The interlayer spacing of rGO could be changed from 9.6 Å to 7.4 Å through control of the oxygen content. The prepared rGO exhibited an excellent adsorption effect on Pb(ii) ions, and the max adsorption capacity reached 194.76 mg g-1 for rGO with a low irradiation dose (5 kGy), which showed that the ratio of oxygen-containing groups is important for improving the adsorption of rGO in aqueous solution. These results indicated that highly efficient, environmentally friendly, and advanced EBI technology has good potential prospects for use in the large-scale production of rGO with precise control of the oxygen content.

Alginate-based composites for environmental applications: A critical review

Alginate-based composites have been extensively studied for applications in energy and environmental sectors due to their biocompatible, nontoxic, and cost-effective properties. This review is designed to provide an overview of the synthesis and application of alginate-based composites. In addition to an overview of current understanding of alginate biopolymer, gelation process, and cross-linking mechanisms, this work focuses on adsorption mechanisms and performance of different alginate-based composites for the removal of various pollutants including dyes, heavy metals, and antibiotics in water and wastewater. While encapsulation in alginate gel beads confers protective benefits to engineered nanoparticles, carbonaceous materials, cells and microbes, alginate-based composites typically exhibit enhanced adsorption performance. The physical and chemical properties of alginate-based composites determine the effectiveness under different application conditions. A series of alginate-based composites and their physicochemical and sorptive properties have been summarized. This critical review not only summarizes recent advances in alginate-based composites but also presents a perspective of future work for their environmental applications.

Colorimetric and Electrochemiluminescence Dual-Mode Sensing of Lead Ion Based on Integrated Lab-on-Paper Device

A highly selective two-point separation strategy was designed based on a cross-like all-in-one lab-on-paper analytical device. The stable and cleavable enzyme-coated reduced graphene oxide (rGO)-PdAu probe was fabricated as the signal reporter to enable the visualization and electrochemiluminescence (ECL) dual-mode sensing of Pb²⁺. Concretely, the experimental workflow consists of the following process: (i) fabrication of the lab-on-paper device and growth of Au nanoparticles on ECL detection zone, (ii) immobilization of Pb²⁺-specific DNAzyme, and (iii) hybridization between DNAzyme and rGO-PdAu-glucose oxidase (GOx) labeled oligonucleotide to form the double-stranded DNA. Upon addition of Pb²⁺ into the prepared system, the double-helix structure of the DNA was destroyed, resulting in the release of cleaved rGO-PdAu-GOx probe to visualization bar to promote the effective oxidation and color change of 3,3',5,5'-tetramethylbenzidine. As a consequence, the color change can be recognized by naked eye, meanwhile GOx on an uncleaved signal probe can oxidize glucose along with the H₂O₂ production. As a co-reaction reagent for luminol ECL system, the concentration of H₂O₂ is proportional to the ECL intensity, which constitutes a new mechanism for colorimetric and ECL dual mode to detect Pb²⁺. With the method developed here, the concentration of Pb²⁺ could be easily determined by the naked eye within a linear range from 5 to 2000 nM, as well as by monitoring the decreased ECL intensity of luminol in a linear range of 0.5-2000 nM. This work not only constructs a simple and versatile platform for on-site visible monitoring of Pb²⁺ in tap water and river water but also furnishes a strategy for designing a dual-mode sensing toward different heavy metal ions based on specific DNAzyme in the fields of environmental monitoring-related technologies.

Silica Aerogel-supported Hydrozincite and Carbonate-intercalated Hydrotalcite for High-efficiency Removal of Pb(II) Ions by Precipitation Transformation Reactions

In this work, hydrozincite and Zn/Al-CO32- hydrotalcite supported on silica aerogel were prepared via a simple and economical process and used as adsorbents for Pb(II) removal. The supported hydrozincite and Zn/Al-CO32- hydrotalcite possess ultra-thin thickness, high surface area, and weak crystallinity. In the batch Pb(II) adsorption experiments, the adsorbents with higher Zn(II) contents showed higher Pb(II) adsorption capacities, and the adsorption data fitted well with the Langmuir isotherm model and pseudo-second-order kinetic model, indicating a mechanism of surface chemisorption. The adsorption capacities calculated based Langmuir isotherm model are 684.9 mg/g and 555.6 mg/g for the supported hydrozincite and Zn/Al-CO32- hydrotalcite, respectively, higher than the adsorption capacities of other hydrotalcite-based adsorbents and most of other inorganic adsorbents reported previously. The XRD diffraction peaks of hydrozincite and Zn/Al-CO32- hydrotalcite disappeared after the adsorption, and the Pb(II) species were uniformly dispersed in the adsorbents in form of Pb3(CO3)2(OH)2 proven by TEM, EDS mapping and XRD analysis, demonstrating the nature of the adsorption is the precipitation conversion of hydrozincite or Zn/Al-CO32- hydrotalcite into Pb3(CO3)2(OH)2. These results demonstrate the synergic Pb(II) removal effect of the CO32- and OH- derived from hydrozincite and Zn/Al-CO32- hydrotalcite together with their ultra-thin thickness and high surface area contribute the excellent properties of the adsorbents.

Remediation Performance and Mechanism of Heavy Metals by a Bottom Up Activation and Extraction System Using Multiple Biochemical Materials

Soil contamination with heavy metals has caused serious environmental problems and increased the risks to humans and biota. Herein, we developed an effective bottom up metals removal system based on the synergy between the activation of immobilization metal-resistant bacteria and the extraction of bioaccumulator material (Stropharia rugosoannulata). In this system, the advantages of biochar produced at 400 °C and sodium alginate were integrated to immobilize bacteria. Optimized by response surface methodology, the biochar and bacterial suspension were mixed at a ratio of 1:20 (w:v) for 12 h when 2.5% sodium alginate was added to the mixture. Results demonstrated that the system significantly increased the proportion of acid soluble Cd and Cu and improved the soil microecology (microbial counts, soil respiration, and enzyme activities). The maximum extractions of Cd and Cu were 8.79 and 77.92 mg kg^-1, respectively. Moreover, details of the possible mechanistic insight into the metal removal are discussed, which indicate positive correlation with the acetic acid extractable metals and soil microecology. Meanwhile, the "dilution effect" in S. rugosoannulata probably plays an important role in the metal removal process. Furthermore, the metal-resistant bacteria in this system were successfully colonized, and the soil bacteria community were evaluated to understand the microbial diversity in metal-contaminated soil after remediation.

β-FeOOH Nanorods/Carbon Foam-Based Hierarchically Porous Monolith for Highly Effective Arsenic Removal

Arsenic pollution in waters has become a worldwide issue, constituting a severe hazard to whole ecosystems and public health worldwide. Accordingly, it is highly desirable to design high-performance adsorbents for arsenic decontamination. Herein, a feasible strategy is developed for in situ growth of β-FeOOH nanorods (NRs) on a three-dimensional (3D) carbon foam (CF) skeleton via a simple calcination process and subsequent hydrothermal treatment. The as-fabricated 3D β-FeOOH NRs/CF monolith can be innovatively utilized for arsenic remediation from contaminated aqueous systems, accompanied by remarkably high uptake capacity of 103.4 mg/g for arsenite and 172.9 mg/g for arsenate. The superior arsenic uptake performance can be ascribed to abundant active sites and hydroxyl functional groups available as well as efficient mass transfer associated with interconnected hierarchical porous networks. In addition, the as-obtained material exhibits exceptional sorption selectivity toward arsenic over other coexisting anions at high levels, which can be ascribed to strong affinity between active sites and arsenic. More importantly, the free-standing 3D porous monolith not only makes it easy for separation and collection after treatment but also efficiently prevents the undesirable potential release of nanoparticles into aquatic environments while maintaining the outstanding properties of nanometer-scale building blocks. Furthermore, the monolith absorbent is able to be effectively regenerated and reused for five cycles with negligible decrease in arsenic removal. In view of extremely high adsorption capacities, preferable sorption selectivity, satisfactory recyclability, as well as facile separation nature, the obtained 3D β-FeOOH NRs/CF monolith holds a great potential for arsenic decontamination in practical applications.

Synergy of adsorption and photosensitization of graphene oxide for improved removal of organic pollutants

The synergic effects of adsorption and photosensitization of graphene oxide were explored here for improved removal of phenolic pollutants.