Solid-state 13C NMR Research Articles

Removal of Cr(VI) from aqueous phase using dimethylaminopropylamine anchored polystyrene‐co‐divinylbenzene polymer as adsorbent

AbstractThe current investigation delves into the effectiveness of dimethylaminopropylamine tethered onto polystyrene‐co‐divinylbenzene polymer for the proficient elimination of hexavalent chromium from simulated wastewater. The resin was characterized using SEM, FT‐IR spectroscopy, EDX, elemental analysis, thermogravimetry, and solid state 13C NMR spectroscopy. The experimental investigation into sorption dynamics involved varying process parameters, including initial Cr(VI) concentration, amount of adsorbent used, solution pH, temperature, and contact between phases. The binding modes of chromate ions, either bidentate or monodentate, were observed, with their manifestation influenced by the solution's pH. Sorption capacity was found to be pH‐dependent, with removal efficiencies of 98.27%, 96.38%, and 85.52% observed at pH levels of 3, 6, and 9, respectively. PS‐DMAPA resin demonstrated robust regeneration capabilities, throughout five consecutive adsorption–desorption cycles. The Langmuir adsorption model exhibited excellent agreement with the experimental findings (R2 = 0.9994), revealing a maximum adsorption capacity of 70.15 mg g−1 at 298 K. Additionally, the experimental findings closely matched the second‐order kinetic model. The kinetics of sorption and the thermodynamic parameters were also investigated. Performance evaluating of the PS‐DMAPA resin under dynamic conditions included analyzing the Cr(VI) breakthrough curve. The 10% sodium chloride solution was employed to effectively recover the extracted Cr(VI) quantitatively.

HOST-GUEST INTERACTIONS FACILITATED BY CHALCOGEN BONDING WITHIN SELENADIAZOLE FUNCTIONALISED PORPHYRIN NANOTUBES.

The structural rigidity of tetrakis(4-pyridyl)porphyrin (TPyP) has been utilised to prepare a robust novel porous coordination polymer of composition Cd2(TPyP)(sez)2 (TPyP = 5,10,15,20-tetra(4-pyridyl)porphyrin, sez = 1,2,5-benzoselenadiazole-5-carboxylate). The coordination polymer may be described as a hexagonal porphyrin nanotube (PNT) and has the potential to bind guest molecules through chalcogen bonding. Single crystal X-ray diffraction (SCXRD) data indicate an internal pore diameter ~9 Å which represents ~35% of the crystal volume. Immersion of the PNTs in solvents such as DMSO and CS2 result in the incorporation of these molecules within the nanotubes with chalcogen bonding between host and guest. The crystallographic guest-inclusion investigations are complemented by solid-state 77Se, 13C, 113Cd and 2H NMR studies which provide insights into dynamic behaviour. The porosity of the crystals was further explored using gas adsorption experiments, indicating the reversible uptake of CO2, CH4, H2 and N2. Structure-function relationships are clearly established from complementary crystallographic, NMR and adsorption investigations.

Record-Breaking H2S Capture and ppm-Level Sensing with a Chemically Stable Porous Organic Cage.

The first experimental investigation of a porous organic cage (POC) for the challenging task of H2S capture is reported. The N-containing cage molecular material, a tertiary amine POC (6FT-RCC3), demonstrates the highest H2S (hydrogen sulfide) capture (record capacity) for a porous material at room temperature and atmospheric pressure (20.6mmol H2S g-1; 25 H2S molecules per cage) combined with excellent reversibility for at least five adsorption-desorption cycles. In situ FTIR spectroscopy, solid-state 13C, and 15N CP MAS NMR spectroscopy experiments are applied to investigate the adsorption mechanism, identifying relatively weak interactions via hydrogen bonding. In addition, the fluorescence performances of this POC material are evaluated for the detection and sensing of H2S, where a clear H2S selectivity is observed over other gases. Remarkably, the limit of detection (LOD) is calculated to be 0.13mm (≈4.43ppm) in a tetrahydrofuran (THF) solution of H2S.

Transforming Nanocrystals into Superhard Boron Carbide Nanostructures.

Boron carbide (B4+δC) possesses a large potential as a structural material owing to its lightness, refractory character, and outstanding mechanical properties. However, its large-scale industrialization is set back by its tendency to amorphize when subjected to an external stress. In the present work, we design a path toward nanostructured boron carbide with greatly enhanced hardness and resistance to amorphization. The reaction pathway consists of triggering an isomorphic transformation of covalent nanocrystals of Na1-xB5-xC1+x (x = 0.18) produced in molten salts. The resulting 10 nm B4.1C nanocrystals exhibit a 4-fold decrease of size compared to previous works. Solid-state 11B and 13C NMR coupled to density functional theory (DFT) reveal that the boron carbide nanocrystals are made of a complex mixture of atomic configurations, which are located at the covalent structural chains between B11C icosahedral building units. These nanocrystals are combined with a spark plasma-sintering-derived method operated at high pressure. This yields full densification while maintaining the particle size. The nanoscaled grains and high density of grain boundaries provide the resulting nanostructured bodies with significantly enhanced hardness and resistance to amorphization, thus delivering a superhard material.

The potential of supramolecular synthon to develop coamorphous systems with tailored physical stability: Mechanistic insights integrating kinetics and thermodynamics

Coamorphous drug delivery systems have received increasing interest owing to their potential to improve the solubility, dissolution and bioavailability of poorly water-soluble drugs. However, the crystallization risk is one of major limitations in their application. It has been widely recognized that the coformer plays a vital role in physical stability of coamorphous formulation. Unfortunately, the screen of optimal coformer still adopts a trial-and-error method, which is time-consuming and expensive. Herein, a supramolecular synthon approach based on the interaction between functional groups, was exploited to design coamorphous systems (CMs) consisting of lurasidone hydrochloride (LH) and three coformers, saccharin (SAC), L-tryptophan (TRP), and L-cysteine hydrochloride (CYS). X-ray powder diffraction suggested the order of physical stability of the coamorphous systems was ranked as LH-CYS CM > LH-TRP CM > LH-SAC CM. The charge-assisted hydrogen bond between LH and coformer was confirmed by infrared spectroscopy and solid-state 13C NMR. Moreover, structural, electronic, and molecular interaction information, especially hydrogen bonding interactions, were quantified by theoretical calculations, including miscibility calculations, molecular dynamics simulations and quantum chemical calculations. It was revealed that LH-CYS CM exhibited the best miscibility, strongest binding energy and strongest H-bond with partially covalent character, demonstrating the significant role of supramolecular synthon in stabilizing coamorphous formulations. Interestingly, LH-TRP CM, not LH-CYS CM, exhibited the lowest molecular mobility among three coamorphous systems, which was inconsistent with their physical stability. But from thermodynamic perspective, the order of configurational entropy and physical stability of coamorphous systems was completely consistent. We shed light on the comprehensive effects of molecular mobility and configurational entropy on physical stability of coamorphous systems. Importantly, the relationship between supramolecular synthon and kinetic/thermodynamic mechanisms was also discussed, and the positive correlation between configurational entropy and intermolecular interactions was proposed in this paper. Our findings demonstrated the great potential of supramolecular synthon in designing coamorphous systems with tailored physical stability, and further provided a deeper insight into the mechanisms of physical stability of coamorphous systems.

Insight into evolution characteristics of pyrolysis products of HLH and HL coal with Py-VUVPI-MS and DFT

To achieve a comprehensive understanding of the influence of chemical structure on the evolution characteristics of coal pyrolysis products, pyrolysis reaction of two kinds of low rank coal (Huolinhe and Huangling coal) were investigated with pyrolysis-vacuum ultraviolet photoionization mass spectrometry (Py-VUVPI-MS). The soft ionized mass spectral detection can provide evolved information of original pyrolysis product. The chemical structure of coal samples was characterized by solid-state 13C-NMR, indicating HLH coal with more branched chain and longer aliphatic chain structure. The bond dissociation enthalpies (BDE) of β-Cal-Cal and β-Cal-O within model compounds were obtained with density functional theory. The difference of peak temperature with maximum evolution was collected to investigate the effect of the chemical environment on evolution behavior of pyrolysis products. The results reveal that branched and long aliphatic side-chains can reduces BDE of β-Cal-Cal and β-Cal-O, resulting in the lower peak temperature of pyrolysis products derived from HLH coal. Substituent groups (such as alkyl and hydroxyl groups) attached on the aromatic rings can reduce peak temperatures. Moreover, the effects of the different substituted position on the aromatic ring of the methyl group presented on differences of the BDE. An increase in aromatic ring size correlates with a certain degree of reduction in BDE for β-Cal-Cal; consequently, peak temperature of pyrolysis products with larger aromatic rings is lower. The pyrolysis behavior of coal were discussed based on the experimental observations and theoretical calculation, which are beneficial to understand the reaction route and mechanism of coal pyrolysis.

Comparative analysis of polysaccharide and cell wall structure in Aspergillus nidulans and Aspergillus fumigatus by solid-state NMR

Invasive aspergillosis poses a significant threat to immunocompromised patients, leading to high mortality rates associated with these infections. Targeting the biosynthesis of cell wall carbohydrates is a promising strategy for antifungal drug development and will be advanced by a molecular-level understanding of the native structures of polysaccharides within their cellular context. Solid-state NMR spectroscopy has recently provided detailed insights into the cell wall organization of Aspergillus fumigatus, but genetic and biochemical evidence highlights species-specific differences among Aspergillus species. In this study, we employed a combination of 13C, 15N, and 1H-detection solid-state NMR, supplemented by Dynamic Nuclear Polarization (DNP), to compare the structural organization of cell wall polymers and their assembly in the cell walls of A. fumigatus and A. nidulans, both of which are key model organisms and human pathogens. The two species exhibited a similar rigid core architecture, consisting of chitin, α-glucan, and β-glucan, which contributed to comparable cell wall properties, including polymer dynamics, water retention, and supramolecular organization. However, differences were observed in the chitin, galactosaminogalactan, protein, and lipid content, as well as in the dynamics of galactomannan and the structure of the glucan matrix.

Design of innovative and low-cost dopamine-biotin conjugate sensor for the efficient detection of protein and cancer cells

The rapid, precise identification and quantification of specific biomarkers, toxins, or pathogens is currently a key strategy for achieving more efficient diagnoses. Herein a dopamine-biotin monomer was synthetized and oxidized in the presence of hexamethylenediamine, to obtain adhesive coatings based on polydopamine-biotin (PDA-BT) on different materials to be used in targeted molecular therapy. Insight into the structure of the PDA-BT coating was obtained by solid-state 13C NMR spectroscopy acquired, for the first time, directly onto the coating, deposited on alumina spheres. The receptor binding capacity of the PDA-BT coating toward 4-hydroxyazobenzene-2-carboxylic acid/Avidin complex was verified by means of UV–vis spectroscopy. Different deposition cycles of avidin onto the PDA-BT coating by layer-by-layer assembly showed that the film retains its receptor binding capacity for at least eight consecutive cycles. Finally, the feasibility of PDA-BT coating to recognize cell lines with different grade of overexpression of biotin receptors (BR) was investigated by tumor cell capture experiments by using MCF-7 (BR+) and HL-60 (BR−) cell lines. The results show that the developed system can selectively capture MCF-7 cells indicating that it could represent a first approach for the development of future more sophisticated biosensors easily accessible, low cost and recyclable with the dual and rapid detection of both proteins and cells.

Synergic Effects of Ordered Mesoporous Bifunctional Ionic Liquid: A Recyclable Catalyst to Access Chemoselective N-Protected Indoline-2,3-dione Analogous

SBA-15 and organic ionic liquid were incorporated in a post-grafting technique for generating a bifunctional ionic liquid embedded mesoporous SBA-15. The prepared heterogeneous catalyst was employed for the first time to synthesize N-alkylated indoline-2,3-dione at mild conditions to afford excellent yields in a short reaction time. The synthesized DABCOIL@SBA-15 catalyst was meticulously characterized by various techniques, such as FT-IR, solid-state 13C NMR, solid-state 29Si NMR, small-angle X-ray diffraction (XRD), and N2 adsorption–desorption. Further, the morphological behavior of the catalyst was studied by SEM and TEM. The thermal stability and number of active sites were determined by thermogravimetric analysis (TGA). The Hammett equation was used to analyze the synergetic effect of the catalyst and substituent effects on the N-alkylated products of 5-substituted isatin derivatives, which resulted in a negative slope. This negative slope indicates a positive charge in the transition state. Notably, the DABCOIL@SBA-15 catalyst demonstrated its practicality by being reused for seven cycles with consistently high catalytic activity.

DNP enhanced solid-state NMR – A powerful tool to address the surface functionalization of cellulose/paper derived materials

This concept summarizes recent advances in development and application of DNP enhanced multinuclear solid-state NMR to study the molecular structure and surface functionalization of cellulose and paper-based materials. Moreover, a novel application is presented where DNP enhanced 13C and 15N solid-state NMR is used to identify structure moieties formed by cross-linking of hydroxypropyl cellulose. Given these two aspects of this concept-type of article, we thus combine both, a review on recent findings already published and unpublished recent data that complement the existing knowledge in the field of characterization of functional lignocellulosic materials by DNP enhanced solid-state NMR.

Bispillar[5]arene-Based Slide-Ring Polyrotaxanation Enables Enhanced Toughness, Recyclability, Impact, and Puncture Resistance of Polyisoprene Elastomers.

A series of slide-ring polyrotaxanes (SRPs) have been constructed by the solvent-free blending of a ditopic pillar[5]arene (DP5A) and polyisoprene (PIP) after thermal annealing. Solid-state 13C NMR experiments supported the fact that the pillar[5]arene rings of DP5A were threaded by PIP chains to afford physically interlocked networks. Tensile tests revealed that 1% of DP5A can improve the elongation at break from 50 to 239%, the tensile modulus from 2.1 to 3.9 MPa, and the toughness from 0.35 to 4.5 MJ/m3. Impact and puncture resistance experiments show that the DP5A-doped materials exhibit remarkable enhancement of protective and impalement-resistant performance. The samples can be also recycled repeatedly due to their physical crosslinking nature. The important stress delocalization effects have been attributed to the pulley effect of DP5A in the SRP materials, which represents a supramolecular approach for improving the performance of PIP elastomers.

Ruthenium nanoparticle immobilised on ionic liquid polymer as efficient catalyst for the hydrolysis of NaBH4

Development of heterogeneous catalyst is significant key for achieving high performance of NaBH4 hydrolysis to produce hydrogen. The stability of sodium borohydride in the presence of suitable catalyst is the efficient method to generate hydrogen. In this work, styrene-imid PIILP, polymer 1 decorated styrene, imidazolium ionic liquid, and cross-coupling is successfully synthesised by AIBN initiated radical polymerisation, then precipitation with 3,3′,3″phosphinetriyltribenzene sulfonate with ratio (1:0.3) to isolate the first styrene-imid- sulphonated PIILP, polymer 2. RuNP@styrene-imid-sulphonated PIILP, RuNPs catalyst 3 was synthesised by impregnation with RuCl3, then reduction by NaBH4. Moreover, several analytical techniques such as, 31P, 1H, 13C solid-state NMR, CHN, IR, XPS, TEM, TGA-DTA, and SEM were examined to explore the obtained catalyst 3. The hydrogen generation from NaBH4 utilizing catalyst 3 was exhibited the catalytic behaviour studying several parameters such as, temperature, catalytic loading, and NaBH4 concentrations this work was deducted the activation energy (30.32 kJmol-1), and the turnover frequency (TOF) reached up 134.9, 112.77, and 98.38 moleH2.molcat−1.min−1 at 40, 35 and 30 °C. The effectiveness of Ruthenium nanoparticle catalyst 3 for the hydrolysis reaction of NaBH4 was examined in H2O and D2O resulting kinetic isotope effect (KIE) kH/kD = 3. In addition, RuNPs demonstrated a promising efficient for reuse catalyst 3 after five cycles for the catalytic hydrolysis.

On the flexibility of 1,4-bis(phenylethynyl)benzene butyl ester organic crystal featuring mobile components

The quest for organic materials with compliant mechanical properties has significantly increased in the past few years in materials science and engineering. Crystalline organic compounds are excellent candidates for exploring and developing those long-lasting properties in the solid state since their fine structural functionalization may provide them with unique flexible behaviors. This study describes the 1,4-bis(phenylethynyl)benzene butyl ester synthesized in four steps and whose crystal can display elastic and elasto-plastic responses upon action with an external stimulus. A detailed characterization by single crystal X-ray diffraction revealed a layered crystal array that results from π-π stacking interactions, C–H⋯O and C-H⋯π bonds. Complementarily, variable temperature solid-state 13C and 2H NMR studies were carried out to probe the motion of the different components of the molecule and explore their possible association with the mechanical features. The compiled evidence indicates that the central phenylenes and the butyl groups experience molecular motion at different timescales, which, combined with the crystal array, facilitate the observed elastic and elasto-plastic flexibility. The results presented here not only contribute to advancing our understanding of flexible behavior but also could inspire potential applications such as flexible electronics.

Efficient Removal of Mercury from Wastewater Solutions by a Nitrogen-Doped Hyper-Crosslinked Polyamine.

Mercury, a highly toxic metal and pollutant, poses a significant risk to human health and the environment. This study describes the synthesis of a new nitrogen-doped heteroaromatic hyper-crosslinked polyamine (HCPA) via the polycondensation of 2,6-diaminopyrazine and tris(4-formylphenyl)amine for the efficient removal of mercury ions from aqueous solutions. The HCPA polymer was characterized by solid-state 13C-NMR and FT-IR spectroscopy. A powder X-ray diffraction and thermogravimetric analysis showed that the polymer was semicrystalline in nature and stable up to 500 °C. Adsorption isotherms indicated that mercury adsorption occurred via mono- and multilayer adsorption by HCPA, as depicted by the Langmuir, Freundlich, and Redlich-Peterson isotherm models, with a maximum adsorption capacity of qm = 333.3 mg/g. Adsorption kinetic models suggested that the adsorption process was fast and effective, reaching equilibrium within 20 min. Thermodynamics of the adsorption process revealed that it was endothermic and spontaneous in nature due to the positive ΔH0 of 48 kJ/mol and negative ΔG0 values of -4.5 kJ/mol at 293 K. Wastewater treatment revealed 98% removal of mercury indicating the selective nature of HCPA. Finally, HCPA exhibited excellent performance and regeneration up to three cycles, demonstrating its great potential as an adsorbent for environmental remediation applications.

Synthesis and application of triptycene based oligomers for the stereoselective aldol reaction of isatin and ketones

Novel triptycene derived oligomers (TOL1, TOL2 and TOL3) with multiple metal-coordinating sites have been synthesized in high yields using a three-component one-pot synthetic protocol and were characterized by various analytical tools such as FT-IR, solid state 13C NMR, GPC and FESEM. The GPC analysis revealed TOLs as oligomers with 8-10 repeating units. The catalytic applications of these oligomers were investigated for the stereoselective synthesis of 3-hydroxy-2-oxindoles via aldol reaction of isatin with ketones by the in-situ complexation of the oligomers with Cobalt metal. All the tested reactions worked well to generate the corresponding products in excellent yields with good diastereo-selectivities.

A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye.

The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1-100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications.

Study of the effect of bleaching agents on the crystalline index of cellulose-based materials derived from corn husk by CP/MAS 13C NMR and FT-IR spectroscopies

This work proposes an evaluation of the Crystalline Index (CrI) in function of the bleaching process employed during cellulose extraction from corn husk, for further characterization using CP/MAS 13C NMR, XRD, and FT-IR. In that sense, CrI values were calculated by FT-IR and the bands associated with the crystalline and amorphous regions were observed at 1424 cm−1 and 896 cm−1, respectively. Similarly, the signals due to ordered (89.1 ppm) and disordered (84.2 ppm) cellulose chains were detected by solid-state 13C NMR, while the Segal equation was only used for comparison purposes. Additionally, PCA studies showed consistent results attributed to the crystalline region in cellulose domains analyzed by both, FT-IR and solid-state 13C NMR. The results revealed the coexistence of cellulose I/cellulose II and its effect on CrI, as well as the incomplete mercerization process, in some cases non-cellulosic residues can cause an overestimation of CrI. Additionally, the thermal stability and the glass transition temperature were determined by TGA/DTA and DSC analyses. Finally, a partially fibrillated-network morphology with a diameter of 20.47 ± 2.77 μm was observed in cellulose bleached with peracetic acid, whereas organosolv method provides flexible and clean microfibrils with diameter sizes between 10 and 9 μm.

Newly synthesised diglycolamide functionalised silica gel with terminal 2-ethylhexyl alkyl chain, Silica-DGA (2EH) having high ligand density for adsorption of trivalent actinide and lanthanide from acidic medium

A novel diglycolamide resin with 2-ethylhexyl terminal alkyl chain functionalised to silica gel was synthesised and characterised by ATR-FTIR, SEM, TG/DSC, &13C (CP/MAS) solid state NMR techniques. Effective functionalization of the organic ligand upon silica gel was confirmed from the two carbonyl stretching frequencies at 1735 cm−1 and 1619 cm−1 in the FTIR spectrum and carbonyl carbon atom signal at 170 ppm in 13C (CP/MAS) solid state NMR spectrum. Thermo gravimetric measurement showed 17.3 ± 0.2 % (W/W) weight loss corresponding to the ligand loading value of 425 µmol/g. The resin showed very high uptake of trivalent lanthanide and actinide ions from 4.0 M HNO3 medium and very low distribution of Cs & Sr; Kd ∼ 1.1×103 mL/g for Am(III), ∼ 1.41×103 mL/g for Eu(III), ∼2.5 mL/g for Sr and 1.53 mL/g for Cs. FTIR spectroscopic study of the Eu3+ adsorbed resin showed single carbonyl stretching frequency at 1654 cm−1, instead of the two carbonyl stretching frequencies in fresh silica-DGA(2EH) resin indicating complexation through carbonyl oxygen. Very low Kd of ∼1.2–5.1 mL/g for lanthanides/actinides from 4.0 M HNO3 containing water soluble DGA namely N, N, N, N, Tetraethyldiglycolamide (TEDGA) in the concentration range 0.3–0.1 M indicates 99 % back adsorption feasibility.

Synergistic effect of CaCO3 particles and porous carbon towards the removal of Zn2+ ions in aqueous solutions

This work describes the preparation of an adsorbent containing CaCO3 particles dispersed in activated carbon and its use for the removal of Zn2+ ions from aqueous solutions. The combination of the large porosity of the activated carbon support with the easy ion exchange occurring at the surface of the carbonate particles led to the achievement of fast adsorption kinetics and excellent ion removal capacity for the composite adsorbent. The material was synthesized by wet impregnation of the porous carbon support with an aqueous solution of Ca(NO3)2, followed by evaporation of the solvent with subsequent heat treatment in an inert atmosphere. X-ray diffraction results demonstrated the presence of CaCO3 crystals in the material, but with broad and low intensity diffraction peaks, corresponding to an average crystallite size of 20 nm; solid-state 13C NMR spectroscopy confirmed the presence of this phase by means of the identification of the signal relative to the 13C nuclei of the CO32− group at ∼170 ppm. The carbon-based adsorbent containing the CaCO3 particles showed excellent ability to remove Zn2+ ions from aqueous solutions, with essentially all ions removed after 30 min of contact time. In addition, the kinetic analysis data were properly fitted using the pseudo-second order model, pointing to the occurrence of chemisorption as the rate limiting of the process. The equilibrium adsorption isotherms were correctly described by the Langmuir model, indicating that the adsorption takes place with the formation of a monolayer on the adsorbent surface. The results evidenced a synergistic effect of the porous carbon and the CaCO3 particles regarding the Zn2+ ions removal, with a fast adsorption kinetics at the initial stage of adsorption attributed to the high availability of the dispersed CaCO3 particles on the carbon surface.

Radiation reduction modification of sp2 carbon-conjugated covalent organic frameworks for enhanced photocatalytic chromium(VI) removal

A sp2 carbon-conjugated covalent organic framework (BDATN) was modified through γ-ray radiation reduction and subsequent acidification with hydrochloric acid to yield a novel functional COF (named rBDATN-HCl) for Cr(VI) removal. The morphology and structure of rBDATN-HCl were analyzed and identified by SEM, FTIR, XRD and solid-state 13C NMR. It is found that the active functional groups, such as hydroxyl and amide, were introduced into BDATN after radiation reduction and acidification. The prepared rBDATN-HCl demonstrates a photocatalytic reduction removal rate of Cr(VI) above 99% after 60 min of illumination with a solid-liquid ratio of 0.5 mg/mL, showing outstanding performance, which is attributed to the increase of dispersibility and adsorption sites of rBDATN-HCl. In comparison to the cBDATN-HCl synthesized with chemical reduction, rBDATN-HCl exhibits a better photoreduction performance for Cr(VI), demonstrating the advantages of radiation preparation of rBDATN-HCl. It is expected that more functionalized sp2 carbon-conjugated COFs could be obtained by this radiation-induced reduction strategy.