Lanthanum ion–impregnated granular activated carbon for the removal of phenol from aqueous solution: Equilibrium and kinetic study

The current study discusses application of the lanthanum ions (La³⁺) as an activating agent incorporated /immobilized into coconut shell–based granular activated carbon (GAC) for porosity development; subsequently, the carbon material is used for the adsorption of phenol from aqueous solutions. The new carbons were characterized using FTIR, XRD, CHNO, burn off, and carbon yield. The surface functional groups were determined by Boehm titration. The Brunauer–Emmett–Teller (BET) surface area of the carbons is 953 m² g⁻¹ (GACLa1073), 997 m² g⁻¹ (GAC383), and 973 m² g⁻¹ (GACO383). Langmuir, Freundlich, Dubinin–Radushkevich, and John–Sivanandan Achari (J-SA) isotherm models on the equilibrium isotherm data were examined for the new carbon-phenol system. It is found that the Langmuir isotherm fits better with a monolayer adsorption capacity, highest for GACLa1073 (387.59 mg g⁻¹) followed by GAC383 (303.03 mg g⁻¹) and GACO383 (197.62 mg g⁻¹). Kinetic studies reveal that the adsorption system follows the pseudo–second-order kinetic model. Isotherm analysis by the phase change method of John-Sivanandan Achari (J-SA) isotherm gives a better insight into adsorption phenomena, which is accompanied by regeneration studies of carbon with >75% for GACLa1073 after three cycles.     

Preparation of an Anti-Aggregation Silica/Zinc/Graphene Oxide Nanocomposite with Enhanced Adsorption Capacity

Nanomaterials play a significant role in adsorption treatment of dye wastewater, but irreversible aggregation of nanoparticles poses a significant problem. In this work, nanomesoporous zinc-doped silicate (NMSZ) was prepared by an in situ method. To prevent agglomeration, NMSZ was covalently bonded to graphene oxide (GO) sheets to form a nano-silica/zinc/graphene oxide composite (GO-NMSZ), aimed at removal of cationic dye methylene blue (MB). For comparison, undoped mesoporous silica (MS) was also synthesized and modified to obtain a silica/graphene oxide composite (GO-MS). The materials were characterized by powder XRD, SEM, FTIR spectroscopy, TEM, nitrogen sorption, and X-ray photoelectron spectroscopy (XPS). Preservation of the oxygen-containing groups of GO in the composites led to higher adsorption capacities. The best GO-NMSZ composite exhibited an enhanced adsorption capacity of 100.4 mg g⁻¹ for MB compared to those of undoped GO-MS (80.1 mg g⁻¹) and nongrafted NMSZ (55.7 mg g⁻¹). The nonselective character of GO-NMSZ is demonstrated by effective adsorption of anionic dye Congo red (127.4 mg g⁻¹) and neutral dye isatin (289.0 mg g⁻¹). The adsorption kinetics, adsorption isotherms, and a thermodynamic study suggested that MB adsorption occurs by chemisorption and is endothermic in nature.     

Performance evaluation of functionalized ordered mesoporous silica for VOCs adsorption by molecular dynamics simulation

Volatile organic compounds (VOCs) are growing pollutants now that cause the serious environmental pollution and threaten human health. The functionalized ordered mesoporous silica (FOMS) has attracted considerable attention in adsorbing VOCs. In this paper, the molecular dynamics simulation was used to simulate the adsorption performance of FOMS on VOCs (acetone, ethyl acetate and toluene). After simulating different pore sizes (2 nm, 3 nm and 4 nm) adsorption performances of ordered mesoporous silica (OMS) on VOCs, OMS with a pore size of 4 nm was selected to further study the influence of functional groups (vinyl, methyl, and phenyl). The following law was obtained: the saturated adsorption capacities of vinyl-functionalized OMS (V-FOMS) to acetone, ethyl acetate and toluene were 3.045 mmol.g^?1, 2.568 mmol.g^?1 and 1.976 mmol.g^?1 respectively; the saturated adsorption capacities of methyl-functionalized OMS (M-FOMS) to acetone, ethyl acetate and toluene were 2.798 mmol.g^?1, 2.312 mmol.g^?1 and 1.698 mmol.g^?1 respectively; the saturated adsorption capacities of phenyl-functionalized OMS (P-FOMS) to acetone, ethyl acetate and toluene were 2.124 mmol.g^?1, 1.941 mmol.g^?1 and 1.539 mmol.g^?1 respectively. These results show that the adsorption ability of FOMS for different adsorbates follows the sequence of acetone > ethyl acetate > toluene. Furthermore, the interaction between functional groups (vinyl, methyl and phenyl) in FOMS and VOCs was explored. It is found that the interaction between different functional groups and adsorbates is different (interaction energy effect). This interaction energy effect promotes FOMS to better adsorb VOCs. This work would provide fundamental understanding and guidance for the development of novel adsorption materials for the adsorption of VOCs.     

Porous graphene oxide-based carbon artefact with high capacity for methylene blue adsorption

A three-dimensional porous graphene oxide (PGO) material prepared by hydrothermal method was selected to adsorb methylene blue (MB), which demonstrates a high MB adsorption capacity, up to 1100 mg g^?1 in alkaline solution at room temperature. The influences of different pore structures and different contents of oxygen-containing functional groups on MB adsorption behaviors were studied in detail, which indicated that the high MB adsorption capacity is mainly ascribed to the synergistic effect of the large number of oxygen-containing functional groups and the interconnected 3D porous network. Moreover, based on the investigation on the adsorption kinetics and the effect of pH value on MB adsorption, we propose a two-step adsorption kinetics for PGO, which involved in two interactions between MB molecular and porous graphene oxide-based carbon: electrostatic force and π-π stacking. Besides, the calculation of the activation energies indicates that chemisorption dominates the adsorption for PGO in comparison with physisorption for three-dimensional porous graphene materials which has low adsorption capacity because of the removal of functional groups. The results are of great significance for the design and environmental applications of PGO as a promising adsorbent material for water purification.     

Adsorption of Dyes from Aqueous Textile By-Products on Activated Carbon from Scenedesmus obliquus

The adsorption of activated carbon prepared from Scenedesmus obliquus (algae) was evaluated through adsorption of Astrazon red. The adsorption efficiency of activated carbon was determined based on the specific surface area and pore size distribution. These results were compared with the results obtained with untreated algae. Approximately a 3-fold increase in the percentage of dye removal was observed for activated carbon compared to the untreated material. The primary reason for this observation may be the increase in specific surface area and total pore volume by chemical activation from 0.0136 to 423.7001?m²?g^?1 and from 0.0012 to 0.1643?cm³?g^?1, respectively. A pseudo-second-order model was fit with the kinetic data and the results indicate chemical adsorption. The maximum adsorption capacity of activated carbon was 181.82?mg?g^?1 at 25°C according to Langmuir isotherm model.     

Poly(hydroxyethyl methacrylate) membranes: as a hydrogel support for use in immobilized metal affinity chromatography

Lysozyme adsorption onto a dye ligand (Procion Red HE-3B) immobilized and Cu(II) incorporated poly(2-hydroxyethylmethacrylate) (pHEMA) membrane, were investigated. The membranes were prepared by UV initiated photopolymerization of HEMA in the presence of an initiator (α-α′-azoisobutyronitrile; AIBN). The amount of immobilized dye on the membrane was 112.2 μmol g⁻¹. Lysozyme adsorption on to these membranes from aqueous solutions containing different amounts of lysozyme at different pH was investigated in batch system. Lysozyme adsorption capacity of the dye-ligand immobilized membrane was 45.6 mg g⁻¹. Lysozyme adsorption capacity of the Cu(II) incorporated membranes (112.3 mg g⁻¹) was greater than that of the Procion Red HE-3B immobilized membranes. The non-specific adsorption of lysozyme on the pHEMA membranes was 0.14 mg g⁻¹. More than 97% of the adsorbed lysozyme were desorbed in 60 in the desorption medium containing 1.0 M KSCN at pH 8.0.     

The preparation of PZS-OH/CNT composite and its adsorption of U(VI) in aqueous solutions

In this paper, polycyclotriphosphazene coated carbon nanotubes (PZS-OH/CNT) composite material has been synthesized via a facial method. The prepared PZS-OH/CNT was characterized by FTIR, BET, zeta potential and SEM. The material was investigated as an adsorbent for the adsorption towards U(VI) from aqueous solutions. Several parameters like solution pH, contact time and temperature were used to evaluate the sorption efficiency. The results indicated that the adsorption capacity of uranium on PZS-OH/CNT was improved from 41.48 mg g⁻¹ for CNT to 338.98 mg g⁻¹ due to the presence of functional groups on PZS-OH/CNT. The U(VI) sorption on PZS-OH/CNT was well fitted to the Langmuir adsorption isotherm and pseudo-second kinetics models. The thermodynamic parameters (ΔH, ΔS and ΔG) showed the U(VI) adsorption on CNT and PZS-OH/CNT was endothermic and spontaneous in nature.

     

Facile synthesis of magnetic hybrid metal–organic frameworks with high adsorption capacity for methylene blue

A magnetic hybrid material (Fe₃O₄‐COOH/HKUST‐1) was easily synthesized via a two‐step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe₃O₄ spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m² g⁻¹) and excellent magnetism (23.65 emu g⁻¹). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g⁻¹), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo‐second‐order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic.     

Corncob-to-xylose residue (CCXR) derived porous biochar as an excellent adsorbent to remove organic dyes from wastewater

Biochar was prepared from corncob-to-xylose residue (CCXR) by KOH activation and anaerobic pyrolysis method. The effect of activation temperature on the microstructure of the biochar was studied. Results showed that the biochar prepared at 850°C (850NBC) possessed high specific surface area and exhibited excellent adsorption property. The maximum adsorption capacity of 2249 mg g⁻¹ was obtained when 850NBC was used for treating methylene blue (MB) solution. Adsorption isotherm fittings revealed that Langmuir and Freundlich models were applicable to 850NBC adsorption process, and the adsorption process was limited by adsorption site and the biochar surface functional groups. Furthermore, 850NBC showed good adsorption property when it was used to treat the other organic dyes of Congo red (751 mg g⁻¹), Orange II (735 mg g⁻¹), Indigo carmine (662 mg g⁻¹) and Methyl Orange (465 mg g⁻¹). Biochar 850NBC also possessed an acceptable recyclability which maintained 68.7% absorption capacity after 6 cycles when it was used to treat MB solution. These results proposed that 850NBC is expected to be a promising potential adsorbent for treating organic dyes waste water.     

Facile Synthesis of Ultrastable Porous Aromatic Frameworks by Suzuki–Miyaura Coupling Reaction for Adsorption Removal of Organic Dyes

Porous aromatic frameworks (PAFs) with robust structure, high stability, and high surface area have attracted intense interest from scientists in diverse fields. However, there are still very few reports on the adsorption of organic dyes by PAFs. In this work, four new PAFs have been facilely synthesized by the polymerization of a tetrahedral-shaped (four-node) monomer with a series of three-node monomers through Suzuki–Miyaura coupling reactions. All the obtained materials possess hierarchical porous structures and show high thermal and chemical stability. The Brunauer–Emmett–Teller (BET) surface areas of these PAFs were determined to be 857 m² g⁻¹ for PAF-111 , 526 m² g⁻¹ for PAF-112A , 725 m² g⁻¹ for PAF-112B , and 598 m² g⁻¹ for PAF-113 . Rhodamine B was selected as a model organic dye to test the adsorption capacities of the obtained PAF materials. PAF-111 showed a maximum adsorption capacity of 1666 mg g⁻¹ (167 wt %) for Rhodamine B, which is among the highest values reported to date for porous organic materials. It is noteworthy that PAF-111 could be reused in at least ten cycles under the adsorption conditions without any loss of adsorption capacity. Our study has revealed the great potential and advantages of PAFs as ultrastable adsorption materials for the removal of organic dyes.     

N-Doped Porous Carbon Derived from Solvent-Free Synthesis of Cross-Linked Triazine Polymers for Simultaneously Achieving CO2 Capture and Supercapacitors

It is highly desirable to design advanced heteroatomic doped porous carbon for wide application. Herein, N-doped porous carbon (NPC) was developed via the fabrication of high nitrogen cross-linked triazine polymers followed by pyrolysis and activation with controllable porous structure. The as-synthesized NPC at the pyrolysis temperature of 700 °C possessed rich nitrogen content (up to 11.51 %) and high specific surface area (1353 m² g⁻¹), which led to a high CO₂ adsorption capability at 5.67 mmol g⁻¹ at 298.15 K and 5 bar pressure and excellent stability. When the activation temperature was at 600 °C, such NPC exhibited a superior electrochemical performance as anode for supercapacitors with a specific capacitance of 158.8 and 113 F g⁻¹ in 6 M KOH at a current density of 1 and 10 A g⁻¹, respectively. Notably, it delivered an excellent stability with capacity retention of 97.4 % at 20 A g⁻¹after 6000 cycles.     

“Activated Borane” – A Porous Borane Cluster Network as an Effective Adsorbent for Removing Organic Pollutants

The unprecedented co-thermolysis of decaborane(14) (nido-B₁₀H₁₄) and toluene results in a novel porous material (that we have named “activated borane”) containing micropores between 1.0 and 1.5 nm in diameter and a specific surface area of 774 m² g⁻¹ (Ar, 87 K) that is thermally stable up to 1000 °C. Solid state ¹H, ¹¹B and ¹³C MAS NMR, UV-vis and IR spectroscopies suggest an amorphous structure of borane clusters interconnected by toluene moieties in a ratio of about three toluene molecules for every borane cluster. In addition, the structure contains Lewis-acidic tri-coordinated boron sites giving it some unique properties. Activated borane displays high sorption capacity for pollutants such as sulfamethoxazole, tramadol, diclofenac and bisphenol A that exceed the capacity of commercially-available activated carbon. The consistency in properties for each batch made, and the ease of its synthesis, make activated borane a promising porous material worthy of broad attention.     

Hierarchical Carbon Nanowire/Ni@MnO2 Nanocomposites for High-Performance Asymmetric Supercapacitors

A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO₂ (CC/N-CNWs/Ni@MnO₂) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO₂ is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO₂ electrode exhibits a higher specific capacitance of 571.4 F g⁻¹ compared with those of CC/N-CNWs@MnO₂ (311 F g⁻¹), CC/Ni@MnO₂ (196.6 F g⁻¹), and CC@MnO₂ (186.1 F g⁻¹) at 1 A g⁻¹ and remarkable rate capability (367.5 F g⁻¹ at 10 A g⁻¹). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO₂ as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg⁻¹ at a power density of 900 W kg⁻¹ and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.     

Ultrastable Surface-Dominated Pseudocapacitive Potassium Storage Enabled by Edge-Enriched N-Doped Porous Carbon Nanosheets

The development of ultrastable carbon materials for potassium storage poses key limitations caused by the huge volume variation and sluggish kinetics. Nitrogen-enriched porous carbons have recently emerged as promising candidates for this application; however, rational control over nitrogen doping is needed to further suppress the long-term capacity fading. Here we propose a strategy based on pyrolysis–etching of a pyridine-coordinated polymer for deliberate manipulation of edge-nitrogen doping and specific spatial distribution in amorphous high-surface-area carbons; the obtained material shows an edge-nitrogen content of up to 9.34 at %, richer N distribution inside the material, and high surface area of 616 m² g⁻¹ under a cost-effective low-temperature carbonization. The optimized carbon delivers unprecedented K-storage stability over 6000 cycles with negligible capacity decay (252 mA h g⁻¹ after 4 months at 1 A g⁻¹), rarely reported for potassium storage.     

Preparation of poly(hydroxyethyl methacrylate-co-methacrylamidohistidine) beads and its design as a affinity adsorbent for Cu(II) removal from aqueous solutions

Different metal-complexing ligands carrying synthetic adsorbents have been reported in the literature for heavy metal removal. We have developed a novel and new approach to obtain high metal adsorption capacity utilizing 2-methacrylamidohistidine (MAH) as a metal-complexing ligand. MAH was synthesized by using methacrylochloride and histidine. Spherical beads with an average size of 150–200 μm were obtained by the radical suspension polymerization of MAH and 2-hydroxyethylmethacrylate (HEMA) conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, p(HEMA-co-MAH) beads had a specific surface area of 17.6 m² g⁻¹. Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling studies, FTIR and elemental analysis. These p(HEMA-co-MAH) affinity beads with a swelling ratio of 65%, and containing 1.6 mmol MAH g⁻¹ were used in the adsorption/desorption of copper(II) ions from metal solutions. Adsorption equilibria was achieved in ∼2 h. The maximum adsorption of Cu(II) ions onto pHEMA was ∼0.36 mg Cu(II) g⁻¹. The MAH incorporation significantly increased the Cu(II) adsorption capacity by chelate formation of Cu(II) ions with MAH molecules (122.7 mg Cu(II) g⁻¹), which was observed at pH 7.0. pH significantly affected the adsorption capacity of MAH incorporated beads. The observed adsorption order under non-competitive conditions was Cu(II)>Cr(III)>Hg(II)>Pb(II)>Cd(II) in molar basis. The chelating beads can be easily regenerated by 0.1 M HNO₃ with higher effectiveness. These features make p(HEMA-co-MAH) beads very good candidate for Cu(II) removal at high adsorption capacity.     

Multilevel Coupled Hybrids Made of Porous Cobalt Oxides and Graphene for High-Performance Lithium Storage

Metal oxide coupling with carbon materials holds great promise for lithium storage. Herein, multilevel coupled cobalt oxide–graphene (CoO/CO₃O₄–G) hybrids were fabricated by in situ assembly of Co hydroxide precursors and a calcination process. The oxygen-containing functional groups on the graphene surface act as bridging sites and tend to bond with Co²⁺ ions, effectively modifying the morphology and structure of the Co species. The as-obtained CoO/CO₃O₄–G hybrids are composed of unique CoO/CO₃O₄ porous nanoparticles uniformly anchored on graphene sheets, as confirmed by a series of characterization analyses. Benefiting from these structural characteristics, the CoO/CO₃O₄–G hybrids used as an anode can deliver a high capacity of about 1080 mA h g⁻¹ reversibly at 0.1 Ag⁻¹ in the voltage range between 3.0 and 0.01 V, which is remarkably superior to that of the CoO hexagonal sheets in the absence of graphene. The high reversible capacity of the CoO/CO₃O₄–G hybrids is retained at elevated current densities, for example, a capacity of approximately 455 mA h g⁻¹ can be achieved at a current rate as high as 4 A g⁻¹, indicative of its potential for high-performance lithium-ion batteries.     

Graphene/Amorphous Carbon Restriction Structure for Stable and Long-Lifespan Antimony Anode in Potassium-Ion Batteries

Sb-based materials have attracted much attention owing to their ability to undergo a multi-electron alloy reaction with K⁺. However, there are still the serious problems of volume change and aggregation of particles, which lead to rapid capacity fading and a limited lifespan. In this work, a graphene/amorphous carbon restriction structure is proposed, in which the amorphous carbon layer on the surface of Sb nanoparticles can protect the particles from pulverization, and the graphene can buffer the volume change of the material. In addition, the conductive network formed by the dual carbon structure effectively improves the rate performance of the material. Thus, the material delivers a high capacity of 550 mA h g⁻¹ at 100 mA g⁻¹, a rate capability of 370 mA h g⁻¹ at 2000 mA g⁻¹, and a long lifespan of 350 cycles without significant capacity fading. The dual carbon strategy proposed offers a reference for the design of high-performance anode materials.     

Optimizing Fe-Based Metal-Organic Frameworks through Ligand Conformation Regulation for Efficient Dye Adsorption and C2H2/CO2 Separation

Regulating the structure of metal-organic frameworks (MOFs) by adjusting the ligands reasonably is expected to enhance the interaction of MOFs on special molecules/ions, which has significant application value for the selective adsorption of guest molecules. Herein, two tricarboxylic ligands H₃L−Cl and H₃L−NH₂ were designed and synthesized based on the ligand H₃TTCA by replacing part of the benzene rings with C=C bonds and modifying the chlorine and amino groups on the 4-position of the benzene ring. Two 3D Fe-MOFs ( UPC-60-Cl and UPC-60-NH₂ ) with the new topology types were constructed. As the C=C bonds of the ligands have flexible torsion angles, UPC-60-Cl features three types of irregular 2D channels, while UPC-60-NH₂ has a cage with two types of windows on the surface. The synergistic effect of unique channels and modification of functional groups endows UPC-60-Cl and UPC-60-NH₂ with high adsorption capacity for organic dyes. Compound UPC-60-Cl shows high adsorption capacity for CV (147.2 mg g⁻¹), RHB (100.3 mg g⁻¹), and MO (220.9 mg g⁻¹), whereas UPC-60-NH₂ exhibits selective adsorption of MO (158.7 mg g⁻¹). Meanwhile, based on the diverse pore structure and modification of active sites, UPC-60-Cl and UPC-60-NH₂ show the selective separation of equimolar C₂H₂/CO₂. Therefore, reasonable regulation of organic ligands plays a significant role in guiding the structure diversification and performance improvement of MOFs.     

Preparation of Ultramicroporous Materials by Fluidized-Bed Pyrolytic Deposition of Carbon in Pores of a Carbon Matrix

Samples of microporous materials were prepared by pyrolytic deposition of carbon from divinyl in a fluidized bed reactor onto carbon supports obtained from coconut and pine nut shells. The influence exerted on the adsorption capacity for CO2 by the divinyl pyrolysis temperature (in the range 600–750°С) and degree of densification (in the range 6–22%) was studied. Carbon deposition conditions ensuring the specific surface area (S_BET) lower than 5 m2 g^–1 at the adsorption capacity for СО₂ higher than 1 mmol g^–1 for both samples were found.     

Synthesis of EDTA-modified magnetic activated carbon nanocomposite for removal of permanganate from aqueous solutions

In this study, activated carbon particles were magnetized by different amounts of maghemite in different temperatures using co-precipitation method and the resultant nanocomposite were modified with ethylenediaminetetraacetic acid (EDTA) to increase the permanganate contaminants adsorption capacity and to prevent degradation and oxidation of maghemite nanoparticles. Various properties of nanocomposite were investigated using different techniques including, vibrating sample magnetometer, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometer. Different kinetics, isotherms and thermodynamic models of adsorption process were investigated. Comparing data with kinetic models showed that the adsorption process complies with the pseudo-second-order kinetic model. The study of equilibrium isotherms data at different temperatures indicated that the adsorption process is more compatible with Langmuir model. Negative values of ΔG and positive values of ΔH revealed that adsorption process is spontaneous and endothermic. Response surface methodology was used to determine optimal parameters of an adsorbent dose of 1 g L⁻¹, pH = 2 and initial permanganate concentration of 50 mg L⁻¹, according to which, the maximum capacity of permanganate adsorption obtained under optimal conditions was 93.86 mg g⁻¹.