Excellent Adsorption Performance Research Articles

Promisingly prioritized elimination performance of europium and uranium from industrial wastewater by recyclable polydopamine functionalized hydroxyapatite/ZIF-67 hybrids

In recent decades, the nuclear industry has undergone robust growth leading to an increasingly severe issues of radionuclide contaminants in wastewater. Consequently, the development of a novel, efficient, regenerative and environmentally friendly adsorbent has become a significant challenge. In this study, recyclable polydopamine functionalized hydroxyapatite/ZIF-67 (HAP/ZIF-67/PDA) hybrids with a mass of functional groups, were successfully synthesized using the ultrasonic-assisted method. The especially characterized techniques illustrated that the HAP/ZIF-67/PDA hybrids were outstanding stable, excellent physicochemical properties and abundant functional groups. The elimination performances of Eu(III) and U(VI) from wastewater were also explored and deliberated through macroscopic experiment under diverse wastewater chemistry environment. The optimal adsorption capacity of HAP/ZIF-67/PDA was approximately 1.33 × 10-3 mol/g for Eu(III) and 8.85 × 10-4 mol/g for U(VI), surpassing those reported materials in previous literatures. The particular adsorption isotherms of Eu(III) and U(VI) were favorably fitted by Langmuir model, illustrating that the adsorption Eu(III) and U(VI) were totally endothermic reaction. The remarkable adsorption performance of HAP/ZIF-67/PDA hybrids (within 80 min for Eu(III) and 100 min for U(VI)) was verified through dynamic model, and then the kinetics results were well simulated through pseudo-second-order kinetic model, which further illustrated outstanding performance for rapidly treating Eu(III) and U(VI) under extreme emergency conditions. The primary adsorption mechanisms HAP/ZIF-67/PDA hybrids towards Eu(III) and U(VI) were surface complexation, competitive interaction, cation change, π-π* bonds and electrostatic interaction. Based on the excellent adsorption performance and recyclability of HAP/ZIF-67/PDA, it holds significantly potential and promising prospects for the efficient elimination of lanthanide and actinium contaminants from the practical treatments and disposals fields of industrial wastewater.

Highly porous P(DVB-AMPS) copolymer with tailored surface engineering for efficient fluoride capture from water

Surface engineering, especially surface hydrophilicity and active binding sites are crucial for porous polymers in the removal of fluoride ions from water. Herein, a novel P(DVB-AMPS) copolymer with tailored surface engineering was designed through a one-step polymerization method by incorporating diethylene-benzene (DVB) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). AMPS endows abundant active binding sites and provides P(DVB-AMPS) with both hydrophilicity and affinity for fluoride ions, while the monomer DVB acting as a crosslinker, facilitating pore generating. The surface hydrophilicity of P(DVB-AMPS) could be easily tuned by increasing the amounts of AMPS with the contact angle decreased from 126° (PDVB) to 52°. Furthermore, P(DVB-AMPS) material maintains a large specific surface area of 428 m2 · g[Formula: see text] and preserves its highly porous structure. P(DVB-AMPS) exhibits an efficient adsorption capacity (51.9 mg · g[Formula: see text]) and a rapid adsorption rate (6.83 mg · g[Formula: see text] · min[Formula: see text]), which demonstrates competitive performance compared with previous reports. Importantly, the material possesses highly selective adsorption toward fluoride. The excellent adsorption performance of P(DVB-AMPS) is attributed to the high porosity, improved surface hydrophilicity and active binding sites. This work not only provides a new strategy for designing high-performance adsorbents but also offers a novel polymer material for the efficient capture of fluoride ions from water.

One-step removal of anionic/cationic heavy metal ions from wastewater by magnetic amphoteric adsorbent

Simultaneous treatment of wastewater containing anionic and cationic pollutants in an easy-to-operate and environmentally friendly manner is a formidable challenge in environmental remediation. This work designed a low-cost and high-efficient amphoteric adsorbent Fe3O4/Mg-Al LDOs/AlS (SMA) for the simultaneous removal of Cr (VI) and Cu (II) pollutants from wastewater in one step. SMA is prepared with waterworks aluminum-containing sludge (AlS) from typical municipal engineering waste as the base material and loaded with magnetic nanoparticles to enhance recycling process after adsorption. SMA exhibits large specific surface area (~418 m2/g), thereby providing sufficient adsorption active sites. Adsorption studies indicate that the adsorption of SMA on two pollutants conforms to the pseudo-second-order kinetic model, while the Langmuir model was used to simulate the adsorption isotherm. The maximum adsorption capacity is calculated to be 235.3 mg/g for Cr (VI) and 669.2 mg/g for Cu (II). Thermodynamic studies reveal the process's spontaneous nature. The main adsorption mechanisms involve electrostatic attraction, surface complexation, isomorphic replacement, and chemical precipitation. Notably, SMA exhibits excellent adsorption performance in a wide pH range and water system containing multiple anions and cations. Moreover, the strong magnetic property facilitates easy separation and recovery through an external magnetic field, maintaining stable adsorption performance even after five cycles. Therefore, this study provides a win-win strategy for promoting environmental safety, not only proposing feasible approaches for the high value-added utilization of waste sludge, but also efficiently addressing the purification problem of complex anionic and cationic coexisting wastewater.

A novel composite electrode with multiple pore structures for efficient treatment of heavy metal ions in capacitive deionization

Multiple porous carbon materials have great promise and potential in the capacitive deionization (CDI) field. Specific surface area (SSA), pore size distribution, and preparation method of CDI electrode materials are essential for the treatment of heavy metal ions. In this work, PPy composited porous carbon electrodes (hypercrosslinked polymers/polypyrrole, HCPs/PPy) were obtained by one-step crosslinked carbonization preparation and electro-deposition. The diverse pore structure gives the composite electrode a large SSA and excellent adsorption performance. HCPs/PPy-4 gives a high SSA of 251.26 m2/g. In the CDI process, the adsorption capacity of HCPs/PPy-4 for Fe3+, Cu2+, Pb2+, and Ag+ is 20.69 mg/g, 37.81 mg/g, 26.86 mg/g, and 40.95 mg/g. The negative electrode recoveries for the adsorption of the four ions were reached 81.2%, 89.2%, 85.5%, and 100%, respectively. It indicates that HCPs/PPy is a novel and potentially porous carbon electrode for high-performance CDI.

Solvent-free synthesis of TiO2 nanoparticles embedded MWCNTs with enhanced photocatalytic activity for bacterial disinfection

Sustainable energy has been widely researched to address issues caused by population growth and rapid industrialization. Among them, photocatalysis using solar energy has been considered promising. We developed a hybrid photocatalyst by combining titanium dioxide (TiO2) with carbon nanotubes (CNTs), known for their excellent adsorption performance. A unique structure encapsulating TiO2 nanoparticles (NPs) within the inner space of multi-walled carbon nanotubes (MWCNTs) was developed via a facile, solvent-free method, conforming to green chemistry principles. Except purification and modification of the CNTs, the particle formation process is solvent-free, making this method remarkably simple and environmentally friendly. This arrangement enhances stability and recyclability, maintaining over 90 % efficiency up to the 3rd cycle. X-ray diffraction (XRD) analysis confirmed that the TiO2 NPs exhibited a crystalline phase, forming exclusively anatase. The defects in the outer walls of the MWCNTs in the composite, coupled with their large specific surface area and dangling bonds, endow them with high adsorption capacity and photocatalytic activity when combined with TiO2 NPs. The MWCNTs@TiO2 composites achieved over 99 % inactivation of Escherichia coli in 60 min and bacteriophage MS2 in 30 min, along with dye adsorption/decomposition. This method offers a distinctive platform for photocatalytic degradation in biological applications and water treatment.

Hydroxyl-functionalized cationic porous organic polymers for efficient enrichment and detection of phenolic endocrine disrupting chemicals in water and snapper

Endocrine-disrupting chemicals (EDCs) can disrupt the normal functioning of the endocrine system in organisms, leading to various health issues. Therefore, monitoring EDCs in the environment and food is of significant importance. In this study, a hydroxyl-functionalized ionic porous organic polymer (OH-IPOP) has been synthesized for the first time using 2-benzimidazolemethanol as a monomer. The OH-IPOP exhibited excellent adsorption performance towards phenolic EDCs. An efficient method for determination of phenolic EDCs (p-tert-butylphenol, bisphenol B, bisphenol A and bisphenol F) in environmental water and snapper samples was successfully established by with OH-IPOP as solid-phase extraction sorbent and determination with high-performance liquid chromatography-ultraviolet detection. The method showed good linearity (r2 > 0.998), low detection limits (0.008–0.020 ng mL−1 for lake water, 1.00–3.00 ng/g for snapper), high recovery rates (82.3–106 %), and good precision (relative standard deviation < 6.6 %), making it a highly efficient adsorbent for the enrichment of EDCs in complex sample matrices.

Reusable biochars derived from Camellia oleifera shell via K2CO3 activated for phenol-enhanced adsorption

Porous biochar materials (BC) have shown excellent performance in energy storage and water treatment adsorption. Carbonization of agricultural and forestry solid waste and fixation in the form of stable biochar to form biochar materials can achieve green "waste utilization for treatment wastewater". In this study, BC samples were generated by using Camellia oleifera shell (COS) as raw material and K2CO3 as green activator in-situ pyrolysis. The adsorption behavior of COS biochar in aqueous solution was evaluated using phenol as a pollutant probe. The synergistic effect of pyrolysis temperature and K2CO3 activation promoted the development of the pore structure of BC. The X-ray photoelectron spectroscopy results indicated that K2CO3 activation promoted the formation of C-C defects and promoted phenol adsorption. KBC-900 exhibited superior absorption capacity for phenol (300.15 mg/g). The activation of K2CO3 also promoted the adsorption of oxygen. In addition, using H2O2 for regenerating biochar did not show a significant decrease in the adsorption rate after five cycles (decline rate < 5 %). The strong adsorption capacity of KBC-900 for phenol might be due to the presence of π-π interactions, hydrogen bonds, and van der Waals interactions during the adsorption process.

Ball milling boosted magnetic cotton husk-derived biochar adsorptive removal of oxytetracycline and ciprofloxacin from water

Oxytetracycline (OTC) and ciprofloxacin (CIP) contamination have caused serious risks to human health, and modified biochar is considered as a potential adsorbent for their removal. The typical agricultural waste of cotton husk was used as the feedstock, then was combined with γ-Fe2O3 and ball milling to innovatively synthesize nano zero-valent iron (nZVI) supporting magnetic cotton hush-derived biochar (Fe2O3@BMBC) by reductive calcination. Fe2O3@BMBC performed excellent adsorption performance with a maximum adsorption capacity for OTC (266.7 mg·g−1) and CIP (83.36 mg·g−1), and its adsorption capacity was 1.6 and 2.3 times that of cotton husk biochar (BC). Characterization analysis showed that Fe2O3@BMBC contained abundant oxygenated functional groups (e.g., -OH, C = O and Fe–O) and its surface was covered by diverse iron oxides. The high magnetization sensitivity of Fe2O3@BMBC guaranteed that it was easily to be separated by a magnet. Oxygenated functional groups (e.g., -OH, C = O and Fe–O) participated in the adsorption process, and solution pH significantly affected the adsorption behaviour, and pseudo-second-order model and Freundlich model better fitting the kinetics and isotherms data. These results confirmed that π-π conjugation, H-bonding, Fe–O complexation and electrostatic interactions contributed to the greater adsorption capacity of Fe2O3@BMBC. Ethanol + ultrasound could efficiently regenerate the used Fe2O3@BMBC and maintain its sustainable adsorption performance for OTC and CIP. Additionally, Fe2O3@BMBC performed a good environmental security in a wide pH range (from 3 to 11) in view of the low leaching risk of Fe.Graphical

Preparation of β-cyclodextrin-reduced graphene oxide aerogel and its application for adsorption of herbicides

Herbicides are the primary pesticides that can easily pollute water bodies, attracting significant attention from researchers regarding the effective removal of herbicide residues from the water environment. In this study, a β-cyclodextrin-reduced graphene oxide (β-CD-BTCA-rGO) aerogel was prepared following the self-assembly hydrothermal method using 1,2,3,4-butane tetracarboxylic acid (BTCA) as crosslinkers. The self-assembly process involved the cross-linking of “soft” β-cyclodextrin (β-CD) with “hard” graphene oxide (GO) nanosheets, forming a stable β-CD-BTCA-rGO aerogel. The prepared β-CD-BTCA-rGO aerogel demonstrated excellent adsorption performance. The adsorption capacities were 62.3 and 46.8 mg/g for sulfentrazone and quinclorac, respectively, surpassing the traditional reduced graphene oxide (rGO) aerogel and citric acid cross-linked (β-CD-CA-rGO) aerogel. Correspondingly, its adsorption capacity for quinclorac was 1.8 times and 12 times that of rGO aerogel and β-CD-CA-rGO aerogel, respectively. Quantum chemical calculations at the density functional theory (DFT) level, utilizing the Fukui function to predict chemical reaction sites, indicated that BTCA, as crosslinkers, formed stable chemical bonds (ester bonds) with GO through hydroxyl and carboxyl surface functional groups, leading to the formation of stable porous aerogels. Furthermore, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap was quantitatively measured for various adsorption mechanisms, revealing that electrostatic adsorption was the main force of the adsorption on the aerogels. The β-CD-BTCA-rGO aerogels prepared in this study demonstrated economic feasibility as adsorbents and exhibited good reproducibility. Consequently, β-CD-BTCA-rGO aerogels hold promising application prospects in the remediation of pesticide pollution in water systems.

Utilizing silica fume and synthetically produced mesoporous silicas for simulated flue gas CO2 adsorption

ABSTRACT Carbon capture and storage (CCS) is crucial in mitigating greenhouse gas emissions. Solid adsorbents, notable for their reusability and corrosion resistance, are gaining attention in CO2 gas separation. This study uses Silica fume as an adsorbent and silica source for SiO2 and MCM-41 silica-based adsorbents. Silica was extracted via an alkaline dissolution method, and adsorbents were synthesized using a CO2-induced precipitation method, chosen for its shorter synthesis time and CO2 utilization. The effects of pore volume, average pore diameter, and specific surface area on amine loading and CO2 adsorption capacity were investigated using CTAB surfactant in SiO2 synthesis, resulting in MCM-41. The synthesized adsorbents were modified with TEPA and DEA amines due to their high affinity for CO2. After determining optimal amine loading, the impact of combining TEPA with DEA was examined. The highest CO2 adsorption capacity under simulated flue gas conditions (15% volume CO2 and 85% volume N2) was 198 milligrams per gram of adsorbent for the SiO2 adsorbent functionalized with 50% by weight amine (28% TEPA and 22% DEA). Variations in CO2 adsorption over time, the influence of adsorbent quantity on adsorption capacity, the affinity of the adsorbent for N2 adsorption, and the adsorption–desorption cycle were investigated. The 28%TEPA-22%DEA-SiO2 adsorbent emerged as the optimal choice due to its large total volume and average pore diameter, absence of a template in its structure, excellent performance in CO2 adsorption, lack of affinity for N2, and robust adsorption–desorption stability.

Synthesis of 4A Zeolite Molecular Sieves by Modifying Fly Ash with Water Treatment Residue to Remove Ammonia Nitrogen from Water

The widespread presence of ammonia nitrogen (NH4+–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH4+–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH4+–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”.

Extended MOF-74-Type Variant with an Azine Linkage: Efficient Direct Air Capture and One-Pot Synthesis.

Direct air capture (DAC) shows considerable promise for the effective removal of CO2; however, materials applicable to DAC are lacking. Among metal-organic framework (MOF) adsorbents, diamine-Mg2(dobpdc) (dobpdc4- = 4,4-dioxidobiphenyl-3,3'-dicarboxylate) effectively removes low-pressure CO2, but the synthesis of the organic ligand requires high temperature, high pressure, and a toxic solvent. Besides, it is necessary to isolate the ligand for utilization in the synthesis of the framework. In this study, we synthesized a new variant of extended MOF-74-type frameworks, M2(hob) (M = Mg2+, Co2+, Ni2+, and Zn2+; hob4- = 5,5'-(hydrazine-1,2-diylidenebis(methanylylidene))bis(2-oxidobenzoate)), constructed from an azine-bonded organic ligand obtained through a facile condensation reaction at room temperature. Functionalization of Mg2(hob) with N-methylethylenediamine, N-ethylethylenediamine, and N,N'-dimethylethylenediamine (mmen) enables strong interactions with low-pressure CO2, resulting in top-tier adsorption capacities of 2.60, 2.49, and 2.91 mmol g-1 at 400 ppm of CO2, respectively. Under humid conditions, the CO2 capacity was higher than under dry conditions due to the presence of water molecules that aid in the formation of bicarbonate species. A composite material combining mmen-Mg2(hob) and polyvinylidene fluoride, a hydrophobic polymer, retained its excellent adsorption performance even after 7 days of exposure to 40% relative humidity. In addition, the one-pot synthesis of Mg2(hob) from a mixture of the corresponding monomers is achieved without separate ligand synthesis steps; thus, this framework is suitable for facile large-scale production. This work underscores that the newly synthesized Mg2(hob) and its composites demonstrate significant potential for DAC applications.

Porous β-cyclodextrin polymers for rapid and efficient removal of organic micropollutants from water: The role of sulfonation and porosity on adsorption performance

Removal of organic micropollutants (OMPs) from water, especially hydrophilic and ionized ones, is challenging for water remediation. Herein, porous β-cyclodextrin polymers (PCPs) with tailored functionalization were prepared based on molecular expansion strategy and sulfonation. Partially benzylated β-cyclodextrin was knotted by external crosslinker to form PCP1, and knotting PCP1 by expansion molecule generated PCP2. PCP1 and PCP2 were sulfonated to achieve PCP1–SO3H and PCP2–SO3H. Based on systematical adsorption evaluation toward multiple categories of OMPs, it was found that the introduced strong polar –SO3H group could bring strong hydrogen bonding and electrostatic interactions. PCP2 showed the highest surface (998.97 m2/g) displayed more excellent adsorption performance toward neutral and anionic OMPs, and the adsorption mechanism for this property of PCP2 was dominated by hydrophobic interactions. In addition, the PCP1–SO3H with the lowest surface area (39.75 m2/g) rather than PCP2–SO3H with higher surface (519.28 m2/g) exhibited more superior adsorption towards hydrophilic and cationic OMPs, benefiting by hydrogen bonding and electrostatic interactions as well as appropriate porosity. These results not only confirmed the performance enhancement of PCPs through the integration of novel preparation strategy, but also provided fundamental guidance for PCPs design for water remediation.

Interface Modulation of 2D Superlattice Heterostructures with Oxygen-enriched Sites and Dissolution Restraint for Effective Rare-earth Elements Extraction

Effective recovery of rare earth elements from wastewater is crucial for the modern industry, as well as for protecting the human health and ecosystem. Nevertheless, it is still challenging to realize efficient and selective low-concentration rare earth extraction in systems containing high levels competing metal ions. Here, we report on the fabrication of two-dimensional superlattice heterostructures (VOGO-x) through the alternating restacking of VOPO4 nanosheets and GO-PDDA nanosheets via electrostatic self-assembly. The meticulously organized molecular scale of superlattice heterostructures enable the full exposure of accessible adsorption sites and facilitate the transport of rare earth ions, meanwhile the abundant oxygen-containing phosphate groups within the interlayer can realize selective rare earth ions extraction. Furthermore, the tunable interlayer interaction can promote structure stability to prevent dissolution. Consequently, VOGO-11 possesses excellent rare earth adsorption performance, with a saturated adsorption capacity (Nd(III) 631.52 mg/g, Dy(III) 689.48 mg/g, Lu(III) 716.06 mg/g), high utilization rate of adsorption sites and short adsorption equilibrium time of simply 10 min in the REE aqueous solution. Furthermore, VOGO-11 exhibits outstanding selective rare earth adsorption ability over a wide range of metal ions in the low-concentration simulated wastewater and actual leaching tailings. These results demonstrate the material’s promising potential in capturing rare earth ions and pave the way to the development of two-dimensional superlattice heterostructures through interface modulation for effective rare earth extraction.

Pore engineering in highly stable hydrogen-bonded organic frameworks for efficient CH4 purification

The unsatisfactory stability of hydrogen-bonded organic frameworks (HOFs) arising from the weakness and flexibility of hydrogen-bonding (H-bonding) has generally hindered their practical applications. By synergistically employing three key strategies: (Ⅰ) introducing charge-assisted H-bonding to increase the polarity of the framework, (Ⅱ) optimizing the length of the building unit by extending the core structure of the linker molecule, and (III) incorporating functional sites containing methoxy and trifluoromethyl, to increase the stability of HOFs and the adsorption affinity for gas molecules, we successfully synthesized three charge-assisted hydrogen-bonded HOFs (NKM-HOF-3, NKM-HOF-4, and NKM-HOF-5; NKM = Nankai Materials). These HOFs exhibit distinct space configurations of nonporous packing, discrete cavities or continuous one-dimensional channels. Notably, NKM-HOF-5 exhibits commendable thermal and chemical stability and can be readily regenerated by re-solvothermal reaction. The activated NKM-HOF-5a exhibits a low affinity for CH4 but captures C2H6 and C3H8 with a relatively high affinity. According to theoretical calculations, the suitable pore size, together with functionalized and polarized surface environments in NKM-HOF-5a contribute to the excellent selective gas adsorption performance of NKM-HOF-5a. Furthermore, the dynamic breakthrough experiments demonstrate the highly efficient separation performance of NKM-HOF-5a for C2H6/CH4, C3H8/CH4, and C3H8/C2H6/CH4.

Preparation of a novel MnO2/red mud composites to enhance arsenic removal

Red mud (RM), an industrial solid waste generated by the alumina industry, is rich in Fe2O3, Al2O3, and SiO2, and has excellent potential for use as a cheap and economical support and as an adsorbent. In this work, a co-precipitation method was used to load MnO2 on RM as an adsorbent (MnRM) to remove As(V) and As(III) from water. The aim was to fully utilize the oxidative properties of MnO2 and the adsorption capacity of Fe-Al oxides/hydroxides in RM to enhance the As(V) and As(III) capacity in water. The experimental data proved that the adsorption performance of MnRM was much better with adsorption capacities of 31.57mg/g and 39.32mg/g for As(V) and As(III), which were 11.29 and 5.71 times higher than that of the raw RM, respectively. Meanwhile, the adsorption capacities of MnRM were also much higher than that of MnO2 for As(V) (18.90mg/g) and As(III) (27.97mg/g). The excellent adsorption performance of MnRM makes it ideal for the treatment of As(V) and As(III) contaminated wastewater.

Study on the adsorption performance of fly ash loaded on nano-FeS for chromium-containing wastewater treatment

In view of the problems caused by chromium-containing wastewater, such as environmental pollution, biological toxicity, and human health risks. Based on fly ash adsorption and nano-FeS reduction characteristics, fly ash loaded nano-FeS composite (nFeS-FA) was synthesized using mineral supported modification technology and ultrasonic precipitation method. The effect of adsorbent dosage, initial pH, contact time, and initial concentration of the solution on the adsorption of Cr(VI) and total Cr by nFeS-FA was investigated. The characteristics of Cr(VI) and total Cr adsorption by nFeS-FA were studied using adsorption isotherms, adsorption kinetics principles, as well as XRD, TEM, SEM-EDS, and BET analysis. The results demonstrated that under the conditions of nFeS-FA of 8 g/L, initial pH of 4, contact time of 150 min, and initial concentration of the solution at 100 mg/L, nFeS-FA achieved removal efficiency of 87.85 % for Cr(VI) and 71.77 % for total Cr. The adsorption of Cr(VI) and total Cr by nFeS-FA followed the Langmuir model and pseudo-second-order kinetic model, indicating monolayer adsorption with chemical adsorption as the dominant mechanism. XRD, TEM, SEM-EDS, and BET revealed that the flaky nano-FeS was uniformly distributed on the surface of fly ash, exhibiting good dispersion and thereby increasing the specific surface area. During the adsorption experiments, nFeS-FA reacted with Cr(VI), and the generated Fe3+ mainly existed as FeOOH precipitation, while S2− reacted with Cr(III) to produce Cr2S3 precipitation. Therefore, nFeS-FA exhibited excellent adsorption performance towards Cr(VI) and total Cr. It can serve as a technological reference for the remediation of heavy metal chromium pollution in the field of water treatment.

Insights into the adsorption performance and mechanism of novel 3D bimetallic MOF nanosheets for the high-efficient removal of 6PPD and 6PPD-quinone

N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) is commonly used as the tire rubber antioxidant, causing widespread contamination in water environments. Moreover, its derivative 6PPD-quinone (6PPD-Q) has been identified as highly toxic to aquatic organisms. Therefore, the urgent environmental concern revolves around the elimination of 6PPD and 6PPD-Q from aquatic settings. In this study, a highly effective 3D bimetallic nanosheet material was initially synthesized for the adsorptive removal of 6PPD and 6PPD-Q. The 3D bimetallic nanosheet materials, Al-TCPP-M (M = Co, Cu, Zn), were prepared by the two-step sequential process, displaying excellent adsorption performance with rates exceeding 97 % and 98 % for 6PPD and 6PPD-Q, respectively. The bimetallic and lamellar structure significantly enhanced the maximum adsorption capacities of Al-TCPP-M (M = Co, Cu, Zn) for 6PPD and 6PPD-Q reaching 331.9–355.9 mg/g and 260.6–335.0 mg/g, respectively. Findings from kinetics and thermodynamics suggested that monolayer adsorption was predominant, primarily driven by chemical adsorption. Additionally, the Al-TCPP-M nanosheets exhibited remarkable reusability and anti-interference ability, and achieved significant removal efficiencies for 6PPD and 6PPD-Q in real river water samples. Furthermore, probable adsorption mechanisms mainly involved hydrogen bonding, electrostatic interactions and π-π stacking. Density functional theory (DFT) calculations proved that the introduction of the second metal increased adsorption active sites of Al-TCPP-M through the formation of π-complexation between transition metals and 6PPD and 6PPD-Q. This research highlights the promising applications of 3D bimetallic MOF nanosheets in environmental remediation.

In situ growth of HKUST-1 on electrospun polyacrylonitrile nanofibers/regenerated cellulose aerogel for efficient methylene blue adsorption

Dyes, as organic pollutants, are causing increasingly severe environmental problems. Metal-organic frameworks (MOFs) are considered promising dye adsorbents; however, their application is limited due to their powder or solid particle forms and limited reusability. Therefore, this study proposes an innovative approach to develop a novel MOF-based composite aerogel, specifically a HKUST-1/polyacrylonitrile nanofibers/regenerated cellulose (HKUST-1/PANNs/RC) composite aerogel adsorbent, for the adsorption of pollutants in water. This adsorbent was successfully prepared using a simple method combining covalent crosslinking, quick freezing, freeze-drying, in-situ growth synthesis, and solvothermal techniques. The HKUST-1/PANNs/RC composite aerogel exhibits a significantly large specific surface area, which is approximately 64 times greater than that of PANNs/RC (10.45 m2·g−1), with a specific surface area of 669.9 m2·g−1. The PANNs serve as a support framework, imparting excellent mechanical properties to the composite aerogel, enhancing its overall stability and recoverability. Additionally, the composite aerogel contains numerous -COOH and -OH groups on its surface, providing strong acid resistance and facilitating interactions with pollutant molecules through electrostatic interactions, π-π conjugation, n-π* interactions, and hydrogen bonding, thereby promoting the adsorption process. Using methylene blue (MB) as a probe molecule, the study results demonstrate that the HKUST-1/PANNs/RC composite aerogel has an adsorption capacity of 522.01 mg·g−1 for MB (25 h), exhibiting excellent adsorption performance. This composite aerogel shows great potential for application in water pollution control.

Adaptive tetralactam macrocycle based polymers for efficient and rapid removal of organic micropollutants with wide scope

With the rapid urbanization and industrialization of human society, water pollution issues caused by the increasing types and quantities of organic micropollutants have become increasingly severe. It is very urgent but also challenging to develop the rapid and efficient method for water purification with a wide removal scope. Herein, a cross-linked polymer adsorbent was fabricated by adaptive tetralactam macrocycle for rapid and efficient removal of multiple types of organic micropollutants in water, including dyes, pharmaceuticals, pesticides, and hormones. The removal efficiencies for the 20 tested organic micropollutants with diverse structures, sizes, and charges are all larger than 95.9 % and approaching 99.9 %, and most of the adsorption processes were finished within 5 min. The well-preorganized and adaptive cavity of tetralactam macrocycle endows the polymer adsorbent with excellent adsorption performance even in extreme conditions. Moreover, the tetralactam macrocycle-crosslinked polymer adsorbent could be regenerated easily and the performance was maintained after 6 cycles. It is demonstrated that the as-developed polymer has great potential in the removal of various hazardous organic pollutants in water.