Dynamic Adsorption Experiments Research Articles

Morphology and surface hydroxyl engineering of H4Nb6O17 nanotubes for enhanced ethyl mercaptan removal

Ethyl mercaptan is usually present in natural gas and biogas, and must be removed due to its toxic, malodorous and corrosive properties. The characteristics content of surface functional groups plays a vital role for the adsorption performance of the adsorbent. In present study, a facile method was proposed to adjust the morphology and structure, as well as the amount of the surface hydroxyl groups of H4Nb6O17 nanotubes. The synthesis of H4Nb6O17 nanotubes with different morphology and structure can adjust the content of surface hydroxyl groups by controlling the flocculation process of [Nb6O17]4- nanosheet sol. By reducing the flocculation rate, more nanosheets are curled to form regular nanotubes, thereby increasing the surface hydroxyl groups of the nanotubes and improving the adsorption capacity of ethyl mercaptan. The dynamic adsorption experiments show that the obtained H4Nb6O17 nanotubes present high ethyl mercaptan adsorption capacity and great cyclic regeneration performance. The high sulfur capacity of H4Nb6O17 nanotubes can be well explained by the abundant surface hydroxyl groups, large specific surface area and hierarchical pore structure. This work provided new insights into design and preparation of high-efficiency adsorbents by morphology and structure engineering.

Investigation of adsorption kinetics of CH4 and CO2 on shale exposure to supercritical CO2

The adsorption kinetics behaviors of CH4 and CO2 on shale are closely related to CO2 sequestration and enhanced shale gas recovery (CS-ESGR). To investigate the influence of supercritical CO2 (ScCO2) exposure on adsorption kinetics behaviors of CH4 and CO2 on shale, X-ray diffraction analysis, low-pressure N2 adsorption and adsorption kinetics experiment of CH4 and CO2 were conducted on raw and ScCO2-treated (10 day/16MPa/40 °C) shale collected from the Ordos Basin. Adsorption rates of CH4 and CO2 by shale were fitted by different adsorption kinetics models, and results indicate that Bangham adsorption (BA) model exhibits a better fitting effect (R2＞0.99) than Pseudo-first-order (PFO) and Pseudo-second-order (PSO) kinetic model and Elovich adsorption (EA) model. After ScCO2 exposure, the adsorption rate of CH4 and CO2 by shale decreased, which may be mainly caused by the decrease of high energy adsorption sites of shale. In addition, the adsorption rate of CO2 by shale is significantly higher than that of CH4, and the influence of pressure on the adsorption rates of CH4 and CO2 is remarkably different, suggesting that the CS-ESGR project should be divided into three stages: Fracturing-Recovery, Replacement-Recovery-Sequestration, and Replacement-Sequestration-Recovery. This study provides a reference for future optimization design of CS-ESGR.

Crayfish shell-based micro-mesoporous activated carbon: Insight into preparation and gaseous benzene adsorption mechanism

The preparation of hierarchically porous carbon via a low-cost way for gaseous benzene adsorption remains a challenge that needs to be addressed urgently. In this study, crayfish shell from kitchen garbage was employed as the precursor for synthesis of activated carbon (AC) via chemical activation strategy, which could be potential in synthesis because of the cost-effective precursor and simple way. Orthogonal design test and various characterization techniques were adopted to explore the optimal preparation conditions of AC. As a result, AC7 with the large specific surface area (2669.40 m2/g) and well-developed pore volume (1.42 cm3/g) has been synthesized successfully. Compared with other adsorbents, AC7 exhibited more excellent adsorption performance for gaseous benzene (684.6 mg/g) in the dynamic adsorption experiments. The influences of preparation factors by the range analysis method and environmental conditions via the single factor method on the adsorption performance of AC7 for gaseous benzene were investigated and analyzed, comprehensively. Based on the isotherm and thermodynamic models, the adsorption experiment data were fitted, analyzed and evaluated to figure out the adsorption mechanism. The results showed that the adsorption process was exothermic, and mainly physical. The partition coefficient and breakthrough volume were also applied to evaluate the benzene adsorption performance objectively. In addition, the reusability tests were carried out. In the eleventh cycle, the adsorption capacities under different initial concentrations were higher than 96.92% of the initial adsorption capacities, showing that AC7 possessed the good reusability. These results showed that AC7 would be an attractive and potential adsorbent for the gaseous benzene adsorption.

Zeolitic Octahedral Metal Oxides with Ultra‐Small Micropores for C2 Hydrocarbon Separation

AbstractSeparation of C2 hydrocarbons, C2H6, C2H4, and C2H2, remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ‐Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

Zeolitic Octahedral Metal Oxides with Ultra-Small Micropores for C2 Hydrocarbon Separation.

Separation of C2 hydrocarbons, C2 H6 , C2 H4 , and C2 H2 , remains significant challenges in chemical industry. However, there are only few adsorbents that can effectively isolate C2 hydrocarbons from their mixtures particularly at a high temperature. Herein, we design a zeolitic octahedral metal oxide based on ϵ-Keggin polyoxometalates with metal ion linkers. Single gas adsorption of the material shows the different adsorption performances for the C2 hydrocarbons and the strong interaction of the material with the C2 hydrocarbons. Dynamic competitive adsorption experiments show that the material efficiently separates each of the binary C2 hydrocarbon mixtures and even the ternary C2 hydrocarbon mixtures with high selectivity. The material keeps high separation performance even the temperature was increased to 85 °C. The material is stable and is able to be reused without loss of the separation performance.

Phosphorus adsorption on the surface of pumice and natural sand adsorbents

Climate change may cause serious implications on the fate of anthropogenic and natural chemicals in water bodies. This condition could lead health problems and environmental destruction. Phosphorus (P) from domestic wastewater released to the water body without proper treatment could lead to eutrophication. Therefore, it is crucial to remove phosphorus from domestic wastewater. Adsorption technology using locally adsorbent materials is a promising alternative method to remove P because of its low cost and effectiveness. In this study, a combination of pumice and sand was investigated to remove phosphorus from the solution. The aim of this study was to study the capacity of local sand and pumice from East Nusa Tenggara (ENTP) to adsorb phosphorus. These adsorbents were characterized using X-ray diffraction, FTIR and XRF followed by isotherm and kinetic adsorption experiments. The results showed that the adsorption of P in these local materials followed the Langmuir model and the P adsorption capacity was 0.07825 mol g−1. The adsorption kinetics followed the second order. Thus, natural pumice can be potentially used as an adsorbent for treating domestic wastewater.

Adsorption Mechanism of Cadmium by Superparamagnetic Nano-Fe3 O4@SiO2 Functionalized Materials

The treatment of cadmium-containing wastewater is of great significance for the emission control of the heavy metal cadmium. Here, a superparamagnetic nano-Fe3O4@SiO2 functionalized material (MFS) was prepared via a co-precipitation method, and the adsorption thermodynamic and kinetic characteristics of Cd2+ were studied by isothermal adsorption tests and kinetic experiments. The adsorption process and mechanism of MFS with respect to Cd2+ were also studied using BET, XRD, and SEM. The Langmuir equation well described the isothermal adsorption characteristics of MFS, and the maximum adsorption capacity was 69.49 mg·g-1. The standard free energy (ΔG), enthalpy (ΔH), and entropy changes (ΔS) showed that the adsorption reaction was a spontaneous, endothermic, and entropic process. The optimal initial pH of the adsorption reaction was 7. The four interfering ions (Mg2+, SO42-, Ca2+, and NO3-) in the solution had a certain inhibitory effect on the adsorption reaction. The pseudo-second-order kinetic model showed that the adsorption process of Cd2+ was divided into two stages, namely a rapid external diffusion stage and a slow internal diffusion stage. The removal rate of Cd2+ was still>73% after using the MFS three times. The BET, XRD, FTIR, and VSM analyses showed that SiO2 was successfully modified on the Fe3O4 surface. MFS is mainly spherical in structure with an average particle size of 38.7 nm and has a saturated magnetic intensity of 85.38 emu·g-1. The XRD, EDS, and XPS analyses revealed that Cd2+ was successfully adsorbed by the material, and the main mechanism was the coordination reaction between Cd2+ and -OH on the surface of the material.

Efficient separation of propylene and propane on SAPO-17 molecular sieve

In this study, the separation performance of propylene and propane on SAPO-17 molecular sieve was investigated by static and dynamic adsorption. The adsorbent possessed good regeneration behavior because the strong adsorption of propylene at room temperature was eliminated by ion exchange treatment. Dynamic adsorption experiments revealed that the kinetic separation selectivity of propylene and propane was as high as 1980, which could be attributed to the energy barrier difference when diffusing through the eight-membered ring of SAPO-17 molecular sieve. The breakthrough experiments verified the good separation performance of the SAPO-17 adsorbent, which suggests that it has considerable application potential in propylene/propane separation.

Facile fabrication of iron-modified biochar as a renewable adsorbent for efficient siloxane (L2) removal

The volatile methylsiloxanes (VMS) in biogas significantly hinders the application. Thus it is vital to identify new materials for achieving the effective removal of VMS from biogas. In this study, iron-modified biochar (FeMBC) materials have been prepared via an impregnation and calcination approach using biochar and Fe (III)-ethanol solution for effective removal of hexamethyldisiloxane (L2). The developed FeMBC materials have been characterized by N2-adsorption/desorption, FTIR, SEM-EDS, XRD and XPS. The results revealed that the as-prepared FeMBC materials possessed a well-developed microporous structure. Among these materials, FeMBC-3 exhibited the highest specific surface area (1068.43 m2 g−1) and micropore volume (0.51 cm3 g−1), leading to an adsorption capacity of 356.4 mg g−1 using 83.82 mg L−1 of L2 with dry N2 as the carrier gas. It was concluded that L2 adsorption capacities were strongly related to the texture of FeMBC materials, especially the pore volume and surface area of micropores. In addition, the influence of temperature and inlet concentration was investigated using dynamic adsorption experiments, and the data were fitted by applying Yoon-Nelson model, Langmuir-Freundlich thermodynamic model and kinetics models, obtaining the thermodynamic and kinetic parameters. The results revealed that the adsorption of L2 on FeMBC-3 was a spontaneous and exothermic process. Finally, regeneration of FeMBC-3 could be swiftly achieved by heating at 100 °C, with the adsorption capacity for L2 remaining stable in the subsequent continuous dynamic adsorption experiments. Thus, the as-prepared FeMBC material represents a promising siloxane adsorbent for biogas up-gradation.

Separation and enrichment of sibiskoside from Sibiraea angustat with magnetic surface dummy template molecularly imprinted polymers

In this work, a novel strategy was developed for separation and enrichment of sibiskoside by dummy molecular imprinting technology and magnetic separation technology. The structural analogue geniposide was selected as the dummy template, using 4-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as the cross-linking agent, and acetonitrile as the porogen. The molecularly imprinted layer was formed on the surface of the magnetic carrier to prepare dummy template molecularly imprinted polymers (DMIPs) with a core–shell structure. The DMIPs were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Vibration sample magnetometer (VSM). The results of adsorption kinetics experiments and isothermal adsorption experiments showed that DMIPs can reach adsorption equilibrium in a short period of time and the maximum adsorption capacity can reach 14.67 mg/g. The imprinting factor was 2.08. Compared with the andrographolide, polydatin, arbutin, caffeic acid, neohesperidin dihydrochalcone and quercetin, DMIPs have good adsorption capacity for the sibiskoside. And the reusability was better. After the adsorption of DMIPs, the purity of sibiskoside in the crude extracts from Sibiraea angustata increased to 78%. It provided a basis for the further development and utilization of Sibiraea angustata as well as the separation and enrichment of monoterpenes.

Phosphorus removal from aqueous solution using Al-modified Pisha sandstone

Pisha sandstone (PS) can increase the ability of sandy soil to retain water and some nutrients due to the presence of montmorillonite, but its inadequate phosphorus adsorption capacity affects its phosphorus holding capacity. This study aims to determine whether Al modification can enhance the phosphate adsorption capacity of Pisha sandstone and to identify the adsorption mechanism. Batch adsorption kinetic and equilibrium isotherm experiments were conducted to investigate the phosphate adsorption behavior of Al-PS (Pisha sandstone modified with Al). The results showed that PS could be successfully modified with Al. As the Al modification ratio increased, the P adsorption capacities of Al-PS increased and the optimal Al-to-PS ratio was 0.81:1. Considering the modification cost and P removal efficiency, it was decided to apply 0.27:1 the Al-to-PS mass ratio in batch adsorption experiments and characterization. The phosphate adsorption capacity decreased but the removal rate increased with increasing amount of Al-PS. The temperature had no significant effect on the adsorption, and the adsorption kinetic and isothermal adsorption data could be well fitted by the pseudo-second-order and Temkin models, respectively. The phosphate adsorption mechanism of Al-PS for phosphate was proposed to be electrostatic adsorption. This study suggested that Al-PS could be considered to be an effective material for phosphate adsorption, and it could enhance the soil phosphorus content when added into sandy soil.

Photodegradation of Reactive Black 5 and raw textile wastewater by heterogeneous photo-Fenton reaction using amino-Fe3O4-functionalized graphene oxide as nanocatalyst

Amino-Fe3O4-functionalized graphene oxide (AmGO) was synthesized and had its photocatalytic properties investigated in the degradation of Reactive Black 5 (RB5) dye and raw textile wastewater (RTW). Graphene oxide was synthesized via modified Hummers method and functionalized with diethylenetriamine and FeCl3 to obtain the AmGO. A 23 factorial design was carried out to optimize the best working conditions; the most statistically significant effect was the AmGO dosage, followed by the initial pH. Kinetics studies were performed and Chan & Chu model the most representative of the experimental data with R2 ≥ 0.95. Experiments of adsorption kinetics were carried out and evidenced that the adsorption of RB5 by AmGO was slower than photodegradation, in which the equilibrium state was reached after 300 min. Moreover, pseudo-second-order model showed the best fit with adsorptive capacity at equilibrium of 53.06 mg∙g−1. AmGO employment in the photodegradation of RB5 exhibited 75 % removal efficiency in less than 2h for the initial dye concentration of 100 mg∙L−1. AmGO also showed satisfactory recycling capacity, since it maintained RB5 removal up to 97 % after 6 cycles. RTW photodegradation experiments exhibited removal efficiencies of 53.25 % for apparent color, and 64.55 % for turbidity. Phytotoxicity assays using cucumber seeds showed low toxicity of the samples after photodegradation, which indicated that toxic compounds were fully mineralized.

Using a Dopamine‐Modified Magnetic Nano‐flower Material for the Solid Phase Extraction of Cyromazine and Melamine in Food Samples

AbstractThis work reported a simple method to prepare MGO@PDA@MoS2 nano‐flower by in situ growth of MoS2 on the poly‐dopamine (PDA) modified Fe3O4@GO (MGO) nanosheets. The novel material was composed of PDA modified MGO nanosheets and flower‐like MoS2 microspheres which two‐dimension ultrathin MoS2 nanosheets were grown in situ on the surface of MGO@PDA and self‐assembled. The material could be used as a new adsorbent for magnetic solid phase extraction (m‐SPE). The nano‐composite was characterized by TG, VSM, SEM, TEM, XRD, XPS and FT‐IR. The extraction parameters were investigated, including initial concentration, extraction time, pH, ionic strength and desorption conditions. The adsorption behaviors of the material were explored via isotherm and kinetic adsorption experiments, which demonstrated that Langmuir adsorption isotherm model and pseudo‐second‐order kinetic model were more appropriate to describe the adsorption process on MGO@PDA@MoS2. A rapid, safe, sensitive, easy, and effective method has been developed for detecting cyromazine and melamine simultaneously in real samples including beef, protein powder and milk by combining with HPLC. Under optimized conditions, the proposed method has a good trueness, wide linear range of 0.1‐100 μg mL−1, low limits of detection (LOD), satisfactory repeatability and reproducibility. Excellent recoveries for the determination of cyromazine and melamine were obtained in spiked real samples. In a word, the nano‐composite material has the advantages of magnetic separation and high adsorption affinity for cyromazine and melamine, and it is a promising adsorbent for extracting cyromazine and melamine from real samples.

Catalytic activation preparation of nitrogen-doped hierarchical porous bio-char for efficient adsorption of dichloromethane and toluene

Volatile organic compounds (VOCs) adsorption by carbonaceous materials is one of the most promising technologies for their efficient abatement, which requires the construction of both suitable porous structures and functional groups. In this work, nitrogen-doped hierarchical porous bio-char (NHWC) was prepared via a facile catalytic activation process, in which NH3·H2O was used as activation agent to introduce nitrogen dopants and trace CaCl2 acted as catalyst for hierarchical pore formation. VOCs dynamic adsorption experiments indicated that the prepared NHWC exhibits excellent dichloromethane and toluene adsorption properties. Particularly, the combined adsorption capacities of dichloromethane and toluene in NHWC are 54.9 and 308 mg g−1, respectively, much higher than those in microporous bio-char, indicating the significant role of hierarchical porosity in multiple VOCs molecules combined adsorption. Control experiments using the prepared model carbon materials indicate that the excellent combined adsorption performance originates from both nitrogen dopants and hierarchical porous structure. Density functional theory calculations further reveal that the introduced nitrogen functional groups enhance the van der Waals interactions between VOCs molecules and carbon surface, thereby improving the combined adsorption of VOCs. This work provides a new strategy of optimizing the pore structure and surface chemistry of bio-char.

Design of Hybrid PAH Nanoadsorbents by Surface Functionalization of ZrO2 Nanoparticles with Phosphonic Acids.

This study focuses on the preparation of innovative nanocomposite materials based on surface modification of commercial nano-ZrO2 optimized from Brønsted acid–base surface reactions. This surface modification was carried out by direct grafting of suitable phosphonic acids bearing a vinylic or phenylic substituent in aqueous solution. Different loading quantities of the anchoring organophosphorus compounds were applied for each materials synthesis. The resulting nanohybrids were thoroughly characterized by infrared spectroscopy (DRIFT), solid-state nuclear magnetic resonance (NMR), nitrogen adsorption-desorption (BET), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS), demonstrating the reliability and efficient tunability of the surface functionalization based on the starting Zr/P ratio. Our nanocomposite materials exhibited a high specific surface area as well as complex porosity networks with well-defined meso-pore. The as-prepared materials were investigated for the adsorption of a mixture of 16 polycyclic aromatic hydrocarbons (PAHs) at 200 ng·mL−1 in an aqueous solution. Adsorption kinetics experiments of each individual material were carried out on the prepared PAHs standard solution for a contact time of up to 6 h. Pretreatments of the adsorption test samples were performed by solid-phase extraction (SPE), and the resulting samples were analyzed using an ultrasensitive GC-orbitrap-MS system. The pseudo-first-order and the pseudo-second-order models were used to determine the kinetic data. The adsorption kinetics were best described and fitted by the pseudo-second-order kinetic model. The correlation between the nature of the substituent (vinylic or phenylic) and the parameters characterizing the adsorption process were found. In addition, an increase of PAHs adsorption rates with phosphonic acid loading was observed.

Trimethylchlorosilane modified activated carbon for the adsorption of VOCs at high humidity

• Hydrophobic coating formed on activated carbon by hydrolysis of TEOS and impregnation of TMCS. • The best condition of TMCS impregnation was investigated. • Morphology and hydrophobicity of activated carbon changed after modification using TMCS. • TMCS modified activated carbon maintains great VOCs adsorption capacity under humid condition. Water vapor is inevitable in practical volatile organic compounds (VOCs) exhaust emission, leading to the deterioration of activated carbon adsorption performance. A hydrophobic modification method of activated carbon (AC) using tetraethyl orthosilicate (TEOS) and trimethylchlorosilane (TMCS) was developed to improve the selectivity of VOCs. A series of characterization and toluene dynamic adsorption experiments at the relative humidity (RH) between 0% and 90% were conducted to find the optimal condition of TMCS and evaluate the modification method. The results showed that TEOS constructed -Si-O-Si- structure and introduced Si-OH to react with TMCS. 30%(w/w) TMCS impregnation for 24 h was an appropriate condition, which improved the water contact angle from 111.6° to 143.6°. When the RH increased from 0% to 60% and 90%, the saturated adsorption capacity of Bare-AC decreased by 45% and 64%, respectively. However, for the TMCS modified activated carbon, the decreases could reduce to only 6% and 9%. At high humidity, the improvement in hydrophobicity compensated the damage of microstructure and provided 52% better toluene adsorption capacity at RH 60%, and 91% better at RH 90%.

Highly efficient adsorptive removal of toluene using silicon-modified activated carbon with improved fire resistance

Activated carbons (ACs) are widely applied in the removal of volatile organic compounds (VOCs) emitted from industrial processes, because of their high adsorption capacity, low cost and reusability. Their poor thermal stability under oxidative conditions is a limiting factor and often leads to fire risk in real applications. Here, Si-modification was performed over a wood-derived AC material, and a series of modified ACs with different Si/C mass ratios (0.1–0.9) were prepared via a hydrothermal route. Physicochemical characteristics of Si/C samples was examined by XRD, SEM, TEM, XPS, FTIR and N2-physisorption measurements. As compared to pristine AC, Si-modified ACs showed enhanced fire resistance, and an increase of ignition temperature by 79 ℃ was achieved at a Si/C mass ratio of 0.9. A combination of TEM, XPS and FTIR characterization suggests that the formation of amorphous SiO2 nanoparticles and SiC species on the surface was responsible for the enhanced fire resistance of Si-modified ACs. By increasing microporosity, Si-modification also significantly improved the adsorption capacity of toluene as a model VOC molecule. Static and dynamic adsorption experiments were performed to understand the adsorption kinetics of the Si-modified ACs. Reusability tests showed that the desorption rate of the modified AC remained at nearly 80% even after five cycles of repeated adsorption-desorption, indicating that the modified AC has a great potential for industrial applications.

Polymer brush-grafted cotton fiber for the efficient removal of aromatic halogenated disinfection by-products in drinking water

Apart from the activated carbon, other functional adsorbents are usually not frequently reported for the removal of disinfection by-products (DBPs) in drinking water. In this study, a novel polymer brush-grafted cotton fiber was prepared and for the first time used as adsorbents for the efficient removal of aromatic halogenated DBPs in drinking water in the column adsorption mode. Poly (glycidyl methacrylate) (PGMA) was grafted onto the surface of cotton fibers via UV irradiation, and then diethylenetriamine was immobilized on the PGMA polymer brush through amination reaction to obtain the aminated cotton fibers (ACFs). The adsorption performance of the prepared ACF was investigated with eight aromatic halogenated DBPs via dynamic adsorption experiments. The results revealed that ACF showed significantly longer breakthrough point (38,500–225,500 BV) for aromatic halogenated DBPs compared with the granular activated carbon (150–500 BV). Thomas model was used to fit the breakthrough curves, and the theoretical value of the maximum adsorption capacity ranged from 14.76 to 89.47 mg/g. The enhanced adsorption performance of the ACF for aromatic halogenated DBPs was mainly due to the formation of hydrogen bonds. Additionally, the partially protonated amine groups also improved the adsorption performance. Furthermore, the ACF also showed remarkable stability and reusability.

Preparation of sulfamethazine molecularly imprinted polymer by electron beam irradiation polymerization

Molecularly imprinted polymers (MIPs) of sulfamethazine (SMZ) were prepared initiated by election beam irradiation in acetonitrile (ACN) with the use of SMZ as template molecule, acrylamide (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent. The combination of SMZ with MaA and EGDMA was studied by infrared spectroscopy. The adsorption kinetics experiment and selectivity of sulfamethazine imprinted polymers were investigated by ultraviolet spectrometry. The experimental results showed that there was a binding effect among SMZ, MAA and EGDMA. When the molar ratio of SMZ, MAA and EGDMA was 1 : 4 : 20, and the irradiation dose was 150 kGy, the adsorption capacity of MIP for sulfamethazine (Q MIP) was the largest (31 mg·g−1). Furthermore, the imprinting factor (F) was 12.91, and the separation factor (α) for SMZ and sulfonamide (SNM) was 1.77.

Preparation of flexible electrospun AOPAN/PVDF membranes for removing Pb2+ from water

Electrospun AOPAN/PVDF composite nanofiber membranes for metal ions treatment have been prepared by coaxial electrospinning. AOPAN shell layer was modified chemically for adsorbing metal ions by chelation, whereas the chemically stable PVDF inner core was for maintaining mechanical stability. Polymer concentration and applied voltage had obvious influence on the characteristics of the fibers’ structure, morphology and strength. The amidoxime reaction was sensitive to the pH value of solution, and it was found that the alkaline condition hindered the reaction. The characterization by SEM, FTIR and XRD showed that the AOPAN/PVDF membrane retained the core–shell structure integrity after chemical modification. In the static and dynamic adsorption experiments, the mechanical strength of the AOPAN/PVDF membrane did not change obviously within 5 cycles of adsorption and regeneration. In addition, the AOPAN/PVDF membranes showed a certain level of efficiency in removal of Pb2+ in aqueous solution; the adsorption capacities of the membranes in the 5th run were higher than 45% of the adsorption of the corresponding fresh membranes. The work provides a potential approach for preparing membranes having good feasibility for practical application in adsorption separation of metal ions.Graphical