One-step ethylene purification from ternary mixtures by an ultramicroporous material with synergistic binding centers.

Developing advanced porous materials with industrial potential to separate multicomponent gas mixtures that are structurally similar is a crucial but challenging task. Here, we report the efficient one-step separation of ethylene (C2H4) from acetylene (C2H2) and carbon dioxide (CO2) using an ultramicroporous metal-organic framework UTSA-16. The synergistic effect of the polarized carboxyl groups and coordinated water molecules in its pore channel enables the material to have high uptakes for C2H2 and CO2 due to electrostatic potential matching, as well as excellent separation selectivity against C2H4. Breakthrough experiments suggest that UTSA-16 can efficiently separate 99.9% pure C2H4 from ternary mixtures with a high productivity of 403 L kg-1. Moreover, the preparation cost of UTSA-16 is significantly lower than other related adsorbents by 40-2000 times, indicating its unique potential for industrial applications.

Efficient recovery of bisphenol A from aqueous solution using K2CO3 activated carbon derived from starch-based polyurethane.

Endocrine-disrupting compounds (EDCs) are increasingly polluting water, making it of practical value to develop novel desirable adsorbents for removing these pollutants from wastewater. Here, a simple cross-linking strategy combined with gentle chemical activation was demonstrated to prepare starch polyurethane-activated carbon (STPU-AC) for adsorbing BPA in water. The adsorbents were characterized by various techniques such as FTIR, XPS, Raman, BET, SEM, and zeta potential, and their adsorption properties were investigated comprehensively. Results show that STPU-AC possesses a large surface area (1862.55 m2·g-1) and an abundance of functional groups, which exhibited superior adsorption capacity for BPA (543.4 mg·g-1) and favorable regenerative abilities. The adsorption of BPA by STPU-AC follows a pseudo-second-order kinetic model and a Freundlich isotherm model. The effect of aqueous solution chemistry (pH and ionic strength) and the presence of other contaminants (phenol, heavy metals, and dyes) on BPA adsorption was also analyzed. Moreover, theoretical studies further demonstrate that hydroxyl oxygen and pyrrole nitrogen are the primary adsorption sites. We found that the efficient recovery of BPA was associated with pore filling, hydrogen-bonding interaction, hydrophobic effects, and π-π stacking. These findings demonstrate the promising practical application of STPU-AC and provide a basis for the rational design of starch-derived porous carbon.

ß-Cyclodextrin functionalized SBA-15 via amide linkage as a super adsorbent for rapid removal of methyl blue.

To remove the bulky aqueous organic dye e.g. methyl blue (MB) from water, ordered mesoporous silica SBA-15 has been functionalized with ß-cyclodextrin (ß-CD) via amide linkage. The surface physical and chemical properties of the surface of the resulted ß-CD-functionalized adsorbents (abbrev. SBA15-A-CD) were characterized systematically. The results indicate that the channels of SBA-15 were uniformly modified with amine groups and were further ß-CD-terminated via amide linkages, without ruining its ordered mesoporous structure. The effects of contact time, pH, ionic strength, temperature and salt on the adsorption performance were explored. SBA15-A-CD showed maximum adsorption capacity for MB up to 1791 mg·g-1 combined with excellent recyclability. Besides, the adsorption behavior of MB onto SBA15-A-CD has been investigated by DFT calculation and two-dimensional NMR. Specifically, the enhanced adsorption capacity for MB stems from the tailored host-guest interaction between ß-CD cavity and aromatic moiety of MB in combination with the electrostatic attraction between amine groups and sulfonated group of MB. These findings offer good opportunities for improving the ability of mesoporous silica in adsorption of bulky anion dyes in wastewater.

Synthesis of carbon quantum dots with iron and nitrogen from Passiflora edulis and their peroxidase-mimicking activity for colorimetric determination of uric acid.

Carbon quantum dots co-doped with iron and nitrogen (Fe@NCDs) were synthesized by using Passiflora edulis Sims (P. edulis) as a precursor. The Fe@NCDs exhibit outstanding peroxidase-mimetic activity owing to successful doping with iron resulting in a behavior similar to that of iron porphyrins. In the presence of H2O2, the Fe@NCDs catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) with a color change from colorless to blue. The blue oxidation product has a characteristic absorption peaking at 652 nm. A colorimetric assay was worked out for uric acid (UA) that measures the hydrogen peroxide produced during oxidation of UA by uricase. Response is linear in the 2-150 µM UA concentration range, and the limit of detection is 0.64 µM. The method was applied to the determination of UA in (spiked) urine, and recoveries ranged from 92.0 to 103.4%. Graphical abstract Schematic representation of the fabrication of iron and nitrogen co-doped carbon dots (Fe@NCDs) using Passiflora edulis Sims as carbon-based materials. First, uric acid (UA) was oxidized to generate H2O2 by uricase. Then, the Fe@NCDs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form blue-colored oxidized TMB (oxTMB) in the presence of H2O2. UA can be quantified based on the theory.

Strong green fluorescent hydrogels with Ba2 MgSi2 O7 :Eu2+ phosphor embedded in cellulose.

Non-cytotoxic and green-emitting fluorescent hydrogels were constructed from a cellulose solution containing Ba2 MgSi2 O7 :Eu2+ green phosphor in a NaOH/urea aqueous system. The structure, optical properties and cytotoxicity of these hydrogels were studied. The Ba2 MgSi2 O7 :Eu2+ phosphor particles were dispersed evenly in the cellulose hydrogel matrix. Good luminescent properties of Ba2 MgSi2 O7 :Eu2+ phosphor were maintained in the hydrogels, leading to strong green emission under ultraviolet excitation. Fluorescent hydrogels have no obvious cytotoxicity in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation test, and have potential use in in vivo applications like optical imaging and drug delivery.

Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin.

Stability of inclusion complex formed by cellulose in NaOH/urea aqueous solution at low temperature.

Cellulose has been demonstrated to be dissolved in 7 wt% NaOH/12 wt% urea aqueous solution pre-cooled to -12 °C, as a result of the formation of inclusion complexes (ICs) associated with cellulose, urea and NaOH. However, this cellulose solution is meta-stable, and IC aggregate could form. In this work, the influences of solvent composition and temperature on the stability of the cellulose ICs in NaOH/urea aqueous solvent system were investigated by dynamic and static light scattering. The stability of cellulose ICs in NaOH/urea aqueous solvent system was firstly enhanced and then lessened with NaOH concentration increasing. The addition of urea slightly enhanced the stability of ICs. Furthermore, the solvent composition had been optimized to reduce the aggregation phenomenon of ICs. The proportion of single cellulose ICs in 9 wt% NaOH/13 wt% urea system increased to 0.96, indicating a stable and better dispersion system of the cellulose ICs. Moreover, temperature exhibited great effect on the IC stability. The molecular weight of cellulose in 9 wt% NaOH/13 wt% urea system at 10 °C reached a low value about 7.6×10(4) g/mol and the single cellulose ICs were predominant species in this case. This work provided a better pathway to characterize the dilute cellulose in NaOH/urea aqueous solution, in which the single cellulose ICs were predominant species.