High Adsorption Selectivity Research Articles

High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO2/N2 and CH4/N2 separation

High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO2/N2 and CH4/N2 separation

Insight into a novel circulation system combined with coordination leaching and biosorption for Cu(II) efficient recycling from electroplating sludge

A novel circulation system combined with coordination leaching and biosorption process was successfully used for the direct recycling of Cu2+ from the electroplating sludge. Cu2+ was firstly efficiently leached out from the sludge by the choosing organic acid, and then it was selectively adsorbed onto a modified sorbent from the lixivium containing other co-ions including Zn2+, Ca2+, Fe3+, Cr3+, and Mg2+ under dynamic adsorption condition. The results of static leaching experiments and DFT calculations showed that citric acid showed the best leaching performance for Cu2+ among the studied organic acids and the traditional inorganic acid (HCl). To selective recovery of Cu2+ from the lixivium, ethylenediamine tetraacetic acid dianhydride (EDTAD) modified bagasse was prepared, and it had high adsorption capacity, selectivity, and good reusability toward Cu-citric acid complex. The adsorption isotherm for Cu matched with the Langmuir model with a maximum adsorption capacity of 52.2 mg/g. XPS and EXAFS analysis illustrated that the Cu-citric acid complex was broken by EDTA on the modified bagasse, and Cu2+ enriched on the sorbent while citric acid was released into the lixivium again. In the combined leaching and sorption circulation system, Cu2+ was simultaneously absorbed on the modified bagasse fixed bed column once it was leached out. Benefitting the recycling of citric acid and the continuous adsorbing of Cu of the circulation system, the leaching efficiency could be increased from 75.0 % to 92.4 %, even in the very dilute citric acid solutions (concentration of 0.01 mol/L). The combined methods could increase Cu recovery efficiency from the sludge at a low concentration of the leaching agent, which had great potential in the practical application.

High-strength ionic hydrogel constructed by metal-free physical crosslinking strategy for enhanced uranium extraction from seawater

Uranium is one of the most important elements in the nuclear industry, and efficient extraction of uranium from the ocean is conducive to the sustainable development of nuclear energy. In this work, rigid perylene tetracarboxylate anion (PTC4−) was introduced by physical (non-covalent) crosslinking strategy to obtain metal-free ionic hydrogel PAOIB-PTC. PTC4− not only increased the rigid structure content of ionic hydrogel, but also formed dynamic macrocycle AO-PTC with amidoxime (AO) through hydrogen bonds. Unlike reported heterogeneous additives, PTC4− did not undergo inhomogeneity or shedding. Therefore, PAOIB-PTC exhibited high strength (7.34 MPa), excellent solvent resistance and salinity tolerance. A large number of hydrophilic groups and multistage pore structure endowed PAOIB-PTC with high hydrophilicity, which facilitated U(VI) mass transfer and led to rapid adsorption rates (88.6 mg g−1 h−1, c0 = 250 ppm). Since the metal-free component enabled more adsorption sites to be utilized, the maximum adsorption capacity of PAOIB-PTC was as high as 1008.03 mg g−1, which exceeded most reported hydrogel-based uranium adsorbents. Experiments and DFT calculations proved that PAOIB-PTC possessed high adsorption selectivity through uranyl recognition via hydrogen bonding and synergistic coordination by supramolecular structure AO-PTC. The low-concentration uranium capture capability and excellent recycling performance demonstrated the practical application potential of PAOIB-PTC. This work provides an idea for the design of metal-free ionic hydrogels with high-strength, and the established PAOIB-PTC is expected to be a candidate material for enhanced uranium extraction from seawater.

Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions

Phytic acid-modified carboxymethyl cellulose (CMC-PA) has been investigated as a promising adsorbent for the removal of uranium from aqueous solutions. The synthesis of CMC-PA involves the hydrogen bonding interaction between CMC and PA, resulting in the incorporation of PA groups onto the cellulose backbone. The hydrophilicity, reusability and adsorption capacity of the prepared CMC-PA hydrogel have improved with the increase of PA content. Moreover, the adsorption experiments were conducted by varying parameters such as pH, initial uranium concentration, and contact time. The results showed that CMC-PA exhibited excellent uranium adsorption performance, with a theoretical maximum adsorption capacity of 436 mg/g. In addition, the material exhibits excellent reusability, and the reusability improves with the increase of crosslinking density, indicating that the crosslinking structure of the polymer gel can effectively enhance the structural stability of the material. Furthermore, CMC-PA also exhibits high selective adsorption performance towards uranium ions in the presence of various competing ions. Its high adsorption capacity, reusability, and selectivity make it a promising candidate for high-performance uranium ion adsorbents.

Piperazine-loaded electrospun fiber mats with MIL-101(Cr, Mg) metal organic framework for CO2 capture

MIL-101(Cr, Mg) is a promising metal organic framework (MOF) considering its moisture, thermal, and chemical stabilities. Piperazine-loaded polyacrylonitrile (PAN)/MIL-101(Cr, Mg) fiber mats were fabricated with different percentages of piperazine (10%, 20%, and 30%) in the polymer solution using an electrospinning technique. The PAN/MIL-101 fiber mats exhibited improved adsorption capacity and selectivity when combined with piperazine because of the improved affinity of CO2 molecules for the basic amine sites of piperazine. PAN/MIL-101–20% was selected as an optimum fiber mat owing to its high CO2 adsorption capacity (2.48 mmol/g) and selectivity (38), which are 2.4 and 2.9 times higher than those of the fiber mat without piperazine, respectively. The stability of the PAN/MOF fiber mat in humid air and NO2 gas and the results of ten adsorption-desorption experiments showed consistent CO2 capture performance.

Ultra-high adsorption capacity and selectivity of photo-enhanced sulfur-rich M2S3 (M[dbnd]Bi and Sb) for gold recovery from electronic wastewater

Recycling gold efficiently from electronic waste (e-waste) not only facilitates the sustainable use of precious resources, but also mitigates environmental risks. In this work, two simple metal sulfides M2S3 (MBi and Sb) microspheres with extraordinary adsorption properties were prepared by a convenient hydrothermal technique for selectively recovering gold from e-waste water. The assistance of visible light significantly improved the gold adsorption performance of M2S3. Two sulfide materials exhibit excellent gold adsorption properties, and the maximum capacity for adsorption reaches 3615.45 mg g−1 for Bi2S3, and 1651.95 mg g−1 for Sb2S3 under optimal conditions and incandescent light irradiation. Gold adsorption on M2S3 materials follows Langmuir and pseudo-second order kinetic models, suggesting that the Au(III) adsorption is dominated by chemisorption in a monolayer adsorption mode. XRD and XPS analysis indicate that the strong sulfur affinity for gold and the photocatalytic reduction-oxidation reaction between Bi2S3 and gold are the main mechanisms for effective gold adsorption on metal sulfides. In addition, M2S3 exhibits excellent gold adsorption selectivity against coexisting ions including Zn(II), Co(II), Cu(II), Fe(III), Ni(II), Mg(II), Ca(II), Al(III) present in actual electronic wastewater. The gold loaded on Bi2S3 was efficiently eluted using acidic thiourea, and the excellent adsorption performance was maintained over five adsorption/desorption cycles. This work presents an effective and simple method for recovering gold(III) from the leachate of discarded electronic devices. Metal sulfides have high adsorption selectivity, ultra-high adsorption capacity, and excellent recyclability, making them a promising green adsorption material for recovering gold from electronic waste.

Dispersive solid phase extraction using a hydrophilic molecularly imprinted polymer for the selective extraction of patulin in apple juice samples

A molecularly imprinted polymer with a specific selectivity for patulin was successfully synthesized. The molecularly imprinted material was prepared using the two functional monomers dopamine and melamine and formaldehyde as the cross-linker. The resulting material possessed a large number of hydrophilic groups, such as hydroxyls, imino groups, and ether linkages. For the first time, uric acid was used as a dummy template for its structural similarity to patulin. Comprehensive characterization and detailed studies of the adsorption process were carried out via adsorption isotherms, while the rate-limiting steps were investigated using adsorption kinetics. Separation, determination, and quantification of patulin were achieved by ultra-high performance liquid chromatography coupled with both photodiode array detection and tandem mass spectrometry. The latter was applied to patulin confirmation in the analysis of real samples. The methodology was validated in 20 apple juice samples. The results showed that the developed hydrophilic molecularly imprinted polymer had high selectivity and specific adsorption towards patulin, with mean recoveries ranging between 85 and 90% and a relative standard deviation lower than 15%. The developed molecularly imprinted polymer exhibited good linearity in the range 1–100 ng mL−1 with coefficient of determination (R2) > 0.99. The limit of detection was 0.5 ng mL−1, and the limit of quantification was 1 ng g−1. The developed method showed a good purification capacity for apple juices due to its hydrophilic nature and the polar interactions established with the target analyte.Graphical abstract

Tailoring the Hydrophobic Interface of Core-Shell HKUST-1@Cu2O Nanocomposites for Efficiently Selective CO2 Electroreduction.

The electrochemical reduction of carbon dioxide (CO2) to ethylene creates a carbon-neutral approach to converting carbon dioxide into intermittent renewable electricity. Exploring efficient electrocatalysts with potentially high ethylene selectivity is extremely desirable, but still challenging. In this report, a laboratory-designed catalyst HKUST-1@Cu2O/PTFE-1 is prepared, in which the high specific surface area of the composites with improved CO2 adsorption and the abundance of active sites contribute to the increased electrocatalytic activity. Furthermore, the hydrophobic interface constructed by the hydrophobic material polytetrafluoroethylene (PTFE) effectively inhibits the occurrence of hydrogen evolution reactions, providing a significant improvement in the efficiency of CO2 electroreduction. The distinctive structures result in the remarkable hydrocarbon fuels generation with high Faraday efficiency (FE) of 67.41%, particularly for ethylene with FE of 46.08% (-1.0V vs RHE). The superior performance of the catalyst is verified by DFT calculation with lower Gibbs free energy of the intermediate interactions with improved proton migration and selectivity to emerge the polycarbon（C2+） product. In this work, a promising and effective strategy is presented to configure MOF-based materials with tailored hydrophobic interface, high adsorption selectivity and more exposed active sites for enhancing the efficiency of the electroreduction of CO2 to C2+ products with high added value.

Ultra-fine potassium hexacyanoferrate(II) nanoparticles modified ZIF-67 for adsorptive removal of radioactive strontium from nuclear wastewater

Development of a material with high adsorption capacity and selectivity for removal of strontium ion (Sr2+) from nuclear wastewater is a challenge. Herein, dodecahedral zeolitic imidazolate frameworks-67 (ZIF-67) was successfully modified by potassium hexacyanoferrate(Ⅱ) (K4Fe(CN)6) nanoparticles, and used as an effective adsorbent for Sr2+ removal from model wastewater. In construction of adsorbent, methanol was used as the medium for assembly of ultra-fine and uniform 25 nm of K4Fe(CN)6 nanoparticles on ZIF-67, well maintaining the original dodecahedral morphology and mesoporous structure of ZIF-67 crystal. N in 2-methylimidazole (2-MI) bonded with Co to generate ZIF-67, while the unsaturated Co in ZIF-67 bonded with N in K4Fe(CN)6 to form spherical nanoparticles. Specific surface area of ZIF-67 were regulated by K4Fe(CN)6 to an appropriate value of 607.464 m2·g−1 for Sr2+ adsorption. Adsorption efficiency of K4Fe(CN)6 modified ZIF-67 for Sr2+ was significantly enhanced to 90 % within 2 h at ambient conditions, due to the improvement in morphology, structure and chemical property of adsorbent. K4Fe(CN)6 modified ZIF-67 exhibited high adsorption selectivity 45 mg·g−1 for Sr2+ in the presence of competing metal ions such as K+, Na+, Mg2+ and Ca2+, and thus achieved 40 mg·g−1 of adsorption capacity for Sr2+ in actual tap water. Adsorption kinetics and isotherms were well fitted with the second-order kinetics and the Langmuir model, respectively, suggesting a chemisorption process. Mechanism studies showed that the surface of ZIF-67 was uniformly covered by ultra-fine nanoparticles, on the outer layer of which K+ ions were distributed as the adsorption sites for ion exchange with Sr2+.

Highly selective recovery of yttrium from mining wastewater using biosynthetic iron sulfide nanoparticles

The selective recovery of rare earth elements (REEs) from mining wastewater has become a hot research topic due to the increasing industrial value of REEs. Herein, biosynthetic iron sulfide nanoparticles (nFeS) were deployed as a superior adsorbent to selectively recover Y(Ⅲ) from mining wastewater. The maximum adsorption efficiency achieved for of Y(Ⅲ) by nFeS was 81.2 % compared to only 38.7 % for Eu(Ⅲ) and 20.8 % for Mn(Ⅱ), demonstrating that nFeS had a high selective adsorption for Y(Ⅲ). To understand the origins of the high selectivity of nFeS, the removal of REEs by the capping layer and the FeS-core were separately investigated. Specifically, given the hard and soft acid base principle (HASB) and the square antiprism coordination geometry of Y(Ⅲ), the adsorption of Y(Ⅲ) by the capping layer was predominantly attributed to CO and –NH2 serving as a monodentate ligand to strongly chelate with Y(Ⅲ), while Y(Ⅲ) interacted with Fe–O on the FeS-core and –COOH more via ion-exchange with Y(Ⅲ). Collectively, cooperative interactions between the capping layer and FeS-core resulted in the overall highly selective adsorption of Y(Ⅲ) by nFeS, suggest this approach has significant potential for future practical remediation and recovery applications to Y(Ⅲ) rich mining wastewaters.

Postsynthetic amine modification of porous organic polymers for CO2 capture and separation

AbstractPorous organic polymers (POPs) constitute an important class of sorbents studied in various adsorption and separation processes. Their unique properties, including high surface areas, adjustable pore sizes, and surface chemistries make them ideal candidates for CO2 capture. To achieve a high CO2 adsorption capacity and selectivity, particularly at the low partition pressures required for post‐combustion CO2 capture or direct capture of CO2 from the atmosphere, incorporating amines onto the polymer frameworks or within the pores has shown much promise. This review provides a comprehensive summary of recent studies on the synthesis and CO2 capture performance of amine‐functionalized POPs. The review also provides a detailed discussion of structure‐performance relationships, focusing on how the loading amount and amine type influence CO2 capture capacity, CO2/N2 selectivity, heat of adsorption, sorption kinetics, and recyclability of POPs. Additionally, the authors offer their perspective on the challenges associated with the practical implementation of amine‐modified POPs for CO2 capture.

Wood frame structured carbons with integrated sieving layer for propylene/propane separation

Adsorption separation of propylene/propane is of great importance in producing the key feedstock of propylene. The core challenge lies in the design of high-performance adsorbent materials capable of high adsorption uptake and selectivity. Here we report a proof-of-concept adsorbent of wood frame structured carbons with an integrated sieving layer, which is prepared on the basis of natural woods by imparting functional polymer layers in the wood cells. The polymer layers in the wood frame penetrate into the wood walls and transform into integrated sieving layer in the resultant carbon honeycombs, rather than block the wood channels. The effective sieving layer as well as the ordered free transport channels enable this type of material to display excellent propylene/propane separation performance, showing a high propylene adsorption uptake of 1.72 mmol g−1, and an ideal adsorbed solution theory and dynamic selectivity up to 3.8 × 104 and 139 at 298 K and 1 bar, respectively. This work provides a unique idea for designing structured carbon adsorbents with selective sieving layer, which may apply to other molecular recognition, separation, and purification processes beyond propylene/propane separation.

Zeolite enhanced iron-modified biocarrier drives Fe(II)/Fe(III) cycle to achieve nitrogen removal from eutrophic water

The problem of nitrogen removal in eutrophic water needs to be solved. Two new autotrophic nitrogen removal technologies, ammonia oxidation coupled with Fe(III) reduction (Feammox) and Nitrate-dependent Fe(II) oxidation (NDFO), have been shown to have the potential to treat eutrophic water. However, the continuous addition of iron sources not only costs more, but also leads to sludge mineralization. In this study, nano-sized iron powder was loaded on the surface of K3 filler as a solid iron source for the extracellular metabolism of iron-trophic bacteria. At the same time, due to the high selective adsorption of zeolite for ammonia can improve the low nitrogen metabolism rate caused by low nitrogen concentrations in eutrophic water, three kinds of modified functional biological carriers were prepared by mixing zeolite powder and iron powder in different proportions (Z1, Zeolite:iron = 1; Z2, Zeolite:iron = 2; Z3, Zeolite:iron = 3). Z3 exhibited the best performance, with removal efficiencies of 54.8% for total nitrogen during 70 days of cultivation. The chemical structure and state of iron compounds changed under microorganism activity. The ex-situ test detected high NDFO and Feammox activities, with values of 1.02 ± 0.23 and 0.16 ± 0.04 mgN/gVSS/h. The enrichment of NDFO bacteria (Gallionellaceae, 0.73%-1.43%–0.74%) and Feammox bacteria (Alicycliphilus, 1.51%-0.88%–2.30%) indicated that collaboration between various functional microorganisms led to autotrophic nitrogen removal. Hence, zeolite/iron-modified biocarrier could drive the Fe(II)/Fe(III) cycle to remove nitrogen autotrophically from eutrophic water without carbon and Fe resource addition.

Hierarchical nanocomposites derived from UiO-66 framework and zeolite for enhanced CO2 adsorption

In this study, a new nanocomposite composed of zeolite Y incorporated into the UiO-66 framework has been synthesized by solvothermal growth of UiO-66 on the support of zeolite Y, and investigated for CO2 adsorption and separation of CO2/CH4 gas mixtures. The aim of this work was to increase the CO2 uptake and the selectivity of the base framework, as well as to increase its thermal stability. Various weight ratios of UiO-66/zeolite Y were prepared to achieve the optimal composition subject to the highest adsorption capacity. The formation of UiO-66/zeolite Y nanocomposites was verified with different characterization methods. It was observed that UiO-66/zeolite Y with a weight ratio of 90:10 has the same morphology as pristine UiO-66 but with superior porosity. Compared to base UiO-66, its surface area and micropore volume increased by about 80 % and 50 %, respectively. Moreover, the results indicate a substantial improvement of 50 % in the CO2 adsorption capacity of nanocomposite (14.6 mmol/g, 298 K, 30 bar) compared to pristine UiO-66. To our knowledge, the newly synthesized nanocomposites exhibited the record-highest CO2 adsorption capacity among the reported UiO-66 composites. The predicted CO2/CH4 adsorption selectivity of the nanocomposite based on IAST is also higher than that of the pristine MOF. Finally, the cyclic adsorption/desorption test revealed more than 95 % desorption efficiency after ten cycles. Due to the high capacity, selectivity, and reversibility of CO2 adsorption on the UiO-66/zeolite Y, and also the high thermal stability of the nanocomposite, it is suggested as an excellent potential adsorbent for the practical application of biogas and natural gas purification. Furthermore, this contribution also presents an insight into the role of zeolite Y in the nanocomposite framework which could comprehend pore size distribution control by varying its amount.

Phenol removal from aqueous media using BEA zeolite: A molecular simulation study on the effect of zeolite mobile cations

Phenol removal from wastewater is crucial due to its high toxicity at low concentrations. In this study, the effectiveness of BEA zeolites (All-Si-BEA, H-BEA, Ca-BEA, and Na-BEA) for phenol removal was investigated using GCMC and MD simulations. The surface area and pore volume of the BEA structures were analyzed. The results showed that All-Si-BEA and H-BEA zeolites had slightly larger pore volumes (less than 2 %) compared to cationic BEA zeolites, indicating minimal impact of cations on pore volume. Efficient phenol adsorption was observed on all zeolite structures, even at low concentrations. All-Si-BEA and H-BEA exhibited high selectivity (105-106) and phenol adsorption capacity (1.86 mmol/g) at low phenol concentrations. Water adsorption was lower on All-Si-BEA and H-BEA, while cationic zeolites had higher water adsorption. The simulations showed that water molecules gather around mobile cations in the pores, causing variation in water adsorption in All-Si-BEA, H-BEA compared to cationic BEAs. The energy examination confirmed this observation. The diffusion coefficients of phenol in BEA (All-Si-BEA, H-BEA, Na-BEA, and Ca-BEA) were 5.34 × 10−5, 3.49 × 10−5, 5.32 × 10−6, and 1.02 × 10−6 (cm2/s), respectively, indicating higher mobility in All-Si-BEA and H-BEA compared to cationic BEA zeolites. Increasing the number of water molecules in the zeolite structures resulted in a decrease in the diffusion coefficient of phenol due to the hindrance caused by water molecules. Overall, All-Si-BEA and H-BEA showed higher potential for phenol separation from water compared to cationic BEA zeolites.

Simultaneous extraction of C3H8 and C2H6 from ternary C3H8/C2H6/CH4 mixtures in an ultra-microporous metal–organic framework

The efficient purification of methane from other light hydrocarbons is of prime importance in natural gas purification. However, the exploitation of stable adsorbents with both high selectivity and high adsorption capacity remains a challenge. Herein, an ultra-microporous Co-based metal–organic framework (Co-MOF) with abundant selective binding sites decorating the pore wall was applied for the highly efficient separation of ternary C3H8/C2H6/CH4 mixtures. The Co-MOF shows remarkable C3H8 and C2H6 adsorption capacities with uptakes of 59.4 cm3/g and 58.6 cm3/g, respectively, while only adsorbing a low amount of CH4 with an uptake of 16.6 cm3/g at 298 K and 100 kPa. The ideal adsorbed solution theory selectivities for C2H6/CH4 (v/v = 50/50) and C3H8/CH4 (v/v = 50/50) reach 26.0 and 290.0 at 298 K, respectively, surpassing most of the state-of-the-art MOF materials. The molecular simulation reveals that the excellent adsorption and separation performance of Co-MOF derives from its suitable pore size and functional pore surfaces. Furthermore, the breakthrough experiments reveal that the Co-MOF exhibits excellent separation performance of C3H8 and C2H6 from natural gas. Notably, the dynamic separation performance of Co-MOF can be well-maintained after five cycles, demonstrating its excellent cycling stability. The high stability and excellent separation performance make Co-MOF a promising adsorbent for natural gas purification.

Toward a mechanistic understanding of Rhenium(VII) adsorption behavior onto aminated polymeric adsorbents: Batch experiments, spectroscopic analyses, and theoretical computations

Rhenium, a rare and critical metal, existing in the industrial wastewater has been aroused extensive interests recently, due to its environmental and resource issues. Chitosan, an easily available, low-cost and eco-friendly biopolymer, was prepared and modified by grafting primary, secondary, tertiary and quaternary amino groups, respectively. Adsorption behaviors and interactions between ReO4− and these four types of aminated adsorbents were investigated through batch experiments, spectroscopic analysis, and theoretical computations. Chitosan modified with secondary amines showed an extremely high uptake of ReO4− with 742.0 mg g−1, which was higher than any reported adsorbents so far. Furthermore, a relatively high adsorption selectivity for Re(VII), as well as the stable and facile regeneration of these aminated adsorbents revealed a promising approach for Re(VII) recovery in full-scale applications. The electrostatic attraction was illustrated to be the main adsorption mechanism by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy analyses. Significantly, the sub-steps of the adsorption process, encompassing the transformation of binding sites and the subsequent binding between these sites and the adsorbate, have been thoroughly investigated through the density functional theory (DFT) calculation method. This approach was firstly proposed to clearly demonstrate the differences in Re(VII) adsorption behavior onto four types of aminated adsorbents, resulting the importance of not only strong binding energy but also an appropriate binding spatial environmental for effective Re(VII) adsorption.

Adsorption and Recognition Property of Tyrosine Molecularly Imprinted Polymer Prepared via Electron Beam Irradiation.

To realize the selective separation of L-tyrosine (L-Tyr) and avoid the drawbacks of traditional thermal polymerization, electron beam irradiation polymerization was developed for the fabrication of L-Tyr molecularly imprinted polymers (MIPs). Firstly, L-Tyr MIPs were prepared with methacrylic acid and ethylene glycol dimethacrylate and without an initiator. Then, the influence of absorbed dosage and temperature on the adsorption capacity of L-Tyr, as well as the thermodynamic behavior, were investigated. The maximum adsorption capacity of 10.96 mg/g for MIPs was obtained with an irradiation dosage of 340 kGy under 15 °C, and the ΔH0 and ΔS0 of the adsorption process are -99.79 kJ/mol and -0.31 kJ/mol·K, respectively. In addition, the effect of adsorption time on adsorption performance was evaluated under different initial concentrations, and the kinetic behavior was fitted with four different models. Finally, the recognition property of the obtained MIPs was investigated with L-Tyr and two analogues. The obtained MIPs have an imprinting factor of 5.1 and relatively high selective coefficients of 3.9 and 3.5 against L-tryptophan and L-phenylalanine, respectively. This work not only provided an L-Tyr MIP with high adsorption capacity and selectivity but also provided an effective and clean method for the synthesis of MIPs.

Ultralight, superhydrophobic and fire-resistant nitrogen-doped graphene aerogel for oil/water separation

The simultaneous achievement of graphene aerogels with low density, high adsorption capacity and selectivity, as well as high mechanical strength, holds great significance but remains a challenging task. By adjusting the concentration and ratio of graphene oxide, dopamine and L-ascorbic acid, the hydrogel without obvious volume shrinkage and stability was synthesized by hydrothermal reaction at low temperature, after freeze-drying and calcination, nitrogen doped graphene aerogel (NGA) with ultralight, superhydrophobic, superoleophilic, fire-resistant, and compressible/recoverable were obtained. The density of NGA is only about 1.9 mg/cm3, and the water and oil contact angles in air are 153.3° and 0°, respectively. Given the aforementioned beneficial features, NGA can efficiently select and adsorb multifarious of oils and organic solvents in oil/water mixtures so as to achieve oil/water separation. Remarkably, NGA exhibits an impressive adsorption capacity of up to 150–305 times its own weight, and it also possesses excellent adsorption recyclability. Therefore, NGA has great potential in the treatment of oil pollution in the water environment.

A novel double-network hydrogel made from electrolytic manganese slag and polyacrylic acid-polyacrylamide for removal of heavy metals in wastewater

Electrolytic manganese slag (EMS), a bulk waste generated in industrial electrolytic manganese production, can be a cost-effective adsorbent for heavy metals removal after appropriate modification. In this study, EMS was activated by NaOH and then used to make the EMS-based double-network hydrogel (an EMS/PAA hydrogel) via a one-pot method. The results showed that the EMS/PAA hydrogel exhibits a high selective adsorption capacity of 153.85, 113.63 and 54.35 mg·g−1 for Pb (II), Cd (II) and Cu (II), respectively. In addition, Density Functional Theory (DFT) suggests that the adsorption energies (Ead) of Pb, Cd and Cu on SiO2/PAA of the EMS/PAA gels are − 4.15, − 1.96, and − 2.83 eV, respectively, and SiO2/PAA, with a strong affinity to Pb2+, is one of the reasons for the selective adsorption capacity of EMS/PAA gel for Pb2+. The removal efficiency of the EMS/PAA gel for Pb2+, Cd2+, Cu2+ decreased after four adsorption-desorption cycles by 20.00 %, 24.56 % and 46.56 %, respectively. Mechanism studies suggested that the elimination of the heavy metals by EMS/PAA gels mainly involves electrostatic attraction, inner-sphere complexation, and coordination interactions. The EMS/PAA hydrogels not only have high adsorption capacity, but are also easy to prepare and circulate, making them ideal for practical applications.