Metal-organic framework MIL-101(Cr) as a sorbent of porous membrane-protected micro-solid-phase extraction for the analysis of six phthalate esters from drinking water: a combination of experimental and computational study.

An attractive metal-organic framework (MOF) MIL-101(Cr) material was synthesized at the nanoscale and applied as a sorbent in the porous membrane-protected micro-solid-phase extraction (µ-SPE) device for the pre-concentration of phthalate esters (PAEs) in drinking water samples for the first time. Parameters influencing the extraction efficiency, such as the selection of sorbent materials, pH adjustment, the effect of salt, magnetic-stirring extraction time, the desorption solvent and the desorption time, were investigated. Under the optimum conditions, the limits of detection from gas chromatography-mass spectrometric analysis for PAEs varied from 0.004 to 0.02 µg L(-1). The linear ranges were from 0.1 to 50 µg L(-1) or from 0.2 to 50 µg L(-1) for the analytes with the relative standard deviations fluctuating from 0.8 to 10.9% (n = 5). The enrichment factors (EFs) for the target PAEs were varied from 143 to 187. MIL-101(Cr) exhibited remarkable advantages compared to activated carbon and MIL-100(Fe). On the other hand, the computational method was first used to predict the adsorption of MIL-101(Cr) towards PAEs. The molecular interactions and the free binding energies between MIL-101(Cr) and PAEs were observed and calculated in terms of the molecular modeling method. MIL-101(Cr) showed high potential in the analysis of PAEs at trace levels in drinking water. The computational result was consistent with the detected enrichment factors. The computational modeling accurately predicted the extraction efficiency of MOF-based material towards the target analytes. Therefore, the combination of experimental and computational study provided a new strategy on the trace contaminant analysis.

Study of competitive adsorption of acid dyes on magnetic quaternary chitosan salt.

Magnetic quaternary chitosan salt CS/EPTAC/Fe3O4 was used for the removal of acid red 1 (AR1), xylenol orange (XO) and alizarin red (AR) in single, binary and ternary systems. In the single system, the maximal adsorption capacity was 781.55 for AR1, 537.40 for XO and 992.61 mg g(-1) for AR at pH 3.0 and 25 °C. The adsorption kinetics of the three dyes followed the pseudo-second-order model. In the multicomponent system, preferential adsorption was observed for AR at low adsorbent quantities due to the small size of the molecule. When the adsorbent amount was greater, AR1 was adsorbed first because of the greater number of sulfonic acid roots. In the entire adsorption process, XO always adsorbed most slowly.

Photocatalysis-PMS oxidation system based on CQDs-doped carbon nitride nanosheets for degradation of residual drugs in water.

Graphite-like carbon nitride (g-C3N4) is favored for its excellent physicochemical properties. However, the high complexation rate of photogenerated carriers greatly limits its practical applications. Based on this, a novel CQDs-doped carbon nitride nanosheets composite (CNS/CQDs) was prepared and applied to the visible light-induced activation of peroxymonosulfate (PMS) for meloxicam (Mel) and tetracycline (TC) degradation. The photocatalytic degradation of Mel and TC were remarkably promoted in the CNS/CQDs+PMS+vis system. Mel photodegradation of 99.90% was achieved over 30 min with 20 mg CNS/CQDs and 20 mg PMS at pH11. And TC photodegradation of 95.97% was achieved over 45 min with 20 mg CNS/CQDs and 20 mg PMS at nature pH6.5. The TOC mineralization rates of Mel and TC were 75.49% and 52.00%, respectively. The transient photocurrent response and electrochemical impedance measurements (EIS) results indicated that the doping of CQDs could improve the charge transfer efficiency of pure g-C3N4, and CNS/CQDs had a low charge transfer resistance. Capture experiments and EPR tests explored the effective actives in the CNS/CQDs+PMS+vis system. Possible degradation pathways of Mel were also analyzed. This study provides valid residual drugs degradation under the dual conditions of visible light catalytic oxidation and persulfate oxidation, which will be a novel perspective for advanced oxidation technology to effectively remove organic pollutants from water.

Microwave-assisted synthesis of defective Ca1-xAgxTi1-yCoyO3 with high photoelectrocatalytic activity for organic pollutant removal from water.

CaTiO3 is considered to be one of the most promising catalysts for the degradation of organic pollutants, but its application is limited by the wide band gap and low catalytic activity. Element doping is an effective strategy to solve these problems. Herein, a novel CaTiO3 co-doped with Ag and Co (Ca1-xAgxTi1-yCoyO3) was synthesized by combining co-precipitation and the microwave hydrothermal method for the first time. The crystal structure, microstructure and light absorption of the material were systematically investigated. The results showed that Ca1-xAgxTi1-yCoyO3 had higher light absorption than pure CaTiO3, and the band gap was reduced to 2.78 eV. First-principles calculations indicated that Ag-Ca and Co-Ti tended to form donor-acceptor defect pairs in the doping process. These defect states not only enhanced the adsorption properties, but also could be used as carrier traps to optimize the dielectric properties of CaTiO3. In the photoelectrocatalytic system, with 0.01 g of catalyst, 98% of methylene blue in 100 mL solution (10 mg L-1) was degraded in 150 min. In addition, Ca1-xAgxTi1-yCoyO3 showed strong stability and excellent recyclability. The double ion co-doping technology will provide an effective strategy for improving the catalytic activity of traditional wide-band gap semiconductors.

Simple fabrication of Chitosan/Graphene nanoplates composite spheres for efficient adsorption of acid dyes from aqueous solution.

A facile method for the fabrication of crosslinked chitosan/graphene nanoplates composite sphere (CS/GNPs) was presented. The obtained samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and thermogravimetric analysis (TGA). The adsorption activities of CS/GNPs for methyl orange (MO) and acid red 1 (AR1) were evaluated such as the effect of pH and GNPs content, as well as adsorption kinetics and isotherms. In view of practical, the reusability of CS/GNPs was also tested. The resulting adsorption capacity for MO is 230.91mgg-1 and 132.94mgg-1 for AR1, respectively. After saturated adsorption, CS/GNPs can be efficiently regenerated and reused with little uptake loss. Therefore, CS/GNPs is the apromising adsorbent with non-toxic, efficient, low-cost and easy to prepare for the dye removal.

A novel magnetic nanoscaled Fe3O4/CeO2 composite prepared by oxidation-precipitation process and its application for degradation of orange G in aqueous solution as Fenton-like heterogeneous catalyst.

In this work, magnetic nanoparticles (MNPs) Fe3O4/CeO2 were firstly synthesized using three different preparation methods, including coprecipitation, impregnation oxidation-precipitation and impregnation reduction-precipitation, respectively. The catalytic activities of Fe3O4/CeO2 MNPs, prepared by above three methods, were compared systematically in terms of the degradation of orange G (OG). The impregnation oxidation-precipitation process was economical and maneuverable due to the usage of air, no need of nitrogen protection and higher utilization efficiency of iron. Response surface methodology based on central composite design were used to investigate the individual and interactive effects of three process parameters on the OG degradation, i.e. the initial pH of the solution, the dosage of H2O2 and the initial concentration of OG. Under the optimal conditions of pH 2.5, H2O2 30 mM, OG 50 mg L-1, catalyst 2.0 g L-1 and 35 °C, the degradation percentage of OG was 98.2% within 120 min, which agreed well with the modeling prediction (R2 = 0.9984, and Adj-R2 = 0.9969). And the degradation reaction well followed the first-order kinetic with R2 = 0.9969. The Fe3O4/CeO2-OX MNPs showed high catalytic activity, stability and reusability in the degradation of OG.

Guanidinylated bioresponsive poly(amido amine)s designed for intranuclear gene delivery.

Guanidinylated poly(amido amine)s with multiple disulfide linkages (Gua-SS-PAAs) were designed and constructed as nonviral gene carriers. The main chains of these novel carriers were synthesized based on monomers containing guanidino groups (guanidine hydrochloride and chlorhexidine), which could avoid complicated side-chain-modification reactions while introducing the guanidino groups. The synthesized Gua-SS-PAAs polymers were characterized by (1)H nuclear magnetic resonance, molecular weight, and polydispersity. Furthermore, Gua-SS-PAAs polymers were complexed with pDNA, and the properties of the complexes were determined, including entrapment efficiency, particle size, ζ-potential, atomic force microscopy images, stability, DNA complexation ability, reduction sensitivity, cytotoxicity, and transfection efficiency. The new Gua-SS-PAAs carriers exhibited higher transfection efficiency and lower cytotoxicity compared with two widely used gene delivery carriers, polyethylenimine and lipofectamine 2000. Furthermore, the relationship between the side-chain structure and morphological/biological properties was extrapolated, and the results showed that guanidine in the side chain aids in the improvement of transfection efficiency. In addition, the introduction of guanidino group might confer the new carriers with nuclear localization function compared to carriers without it.

[Adsorption behavior of anionic dyes onto magnetic chitosan derivatives].

Adsorption of acid red 1 (AR1) and xylenol orange (XO) onto magnetic quaternary chitosan particles were studied through the static adsorption method. The results showed that, the maximal adsorption capacities calculated by Langmuir equations were 781.55 mg x g(-1) for AR1, 537.40 mg x g(-1) for XO at pH 3.0 and 25 degrees C. The constant n obtained by Frendlich equations were 1.71 and 1.92 respectively, which reflected the favourable adsorption of the dyes onto CS/EPTAC/Fe3O4. Temkin equations showed that heterogeneous surface of adsorbent was the main adsorption point. The adsorption kinetics of two kinds of dyes followed the pseudo-second-order model, which indicated the process was mainly chemical adsorption. Compared with the powder activated carbon, CS/EPTAC/Fe3O4 showed advantages of excellent adsorption performance, rapid separation and easy regeneration.

Ultrasound-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet followed by gas chromatography for the determination of eight pyrethroid pesticides in tea samples.

A novel ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet method (UA-DLLME-SFO) combined with gas chromatography (GC) was developed for the determination of eight pyrethroid pesticides in tea for the first time. After ultrasound and centrifugation, 1-dodecanol and ethanol was used as the extraction and dispersive solvent, respectively. A series of parameters, including extraction solvent and volume, dispersive solvent and volume, extraction time, pH, and ultrasonic time influencing the microextraction efficiency were systematically investigated. Under the optimal conditions, the enrichment factors (EFs) were from 292 to 883 for the eight analytes. The linear ranges for the analytes were from 5 to 100µg/kg. The method recoveries ranged from 92.1% to 99.6%, with the corresponding RSDs less than 6.0%. The developed method was considered to be simple, fast, and precise to satisfy the requirements of the residual analysis of pyrethroid pesticides.

[Preparation of magnetic quaternary chitosan salt and its adsorption of methyl orange from water].

First, quaternary chitosan salts with different substitution degrees were prepared in glycine hydrochloride ([Gly]Cl) ionic liquid. Nano-sized Fe3O4 powder was obtained through chemical co-precipitation method. And then, magnetic quaternary chitosan particles were prepared through inverse suspension cross-linking using Fe3O4 was the nucleus and glutaraldehyde as the cross-linking agent. The influence of different reaction conditions on adsorption was discussed. Adsorption of methyl orange (MO) by magnetic quaternary chitosan particles was studied through the static adsorption method. The results showed that at pH 3.0 and 25 degrees C the adsorption capacity varied from 37.45 mg x g(-1) to 277.5 mg x g(-1) with the MO concentration ranging from 20 mg x L(-1) to 150 mg x L(-1). The adsorption isotherm was fitted to the Freundlich model and the adsorption kinetics was fitted to the pseudo-second order kinetic isotherms capacity experiment. It was found that after the adsorbent was used for four times, its removal rate still exceeded 90%.