•Metastable Bi3+ self doped NaBiO3 nanosheets were successfully prepared.•Metastable self doped NaBiO3 could generate singlet oxygen.•Metastable self doped NaBiO3 showed enhanced photocatalytic activity.•Visible light enhanced the generation of singlet oxygen from self doped NaBiO3.•Carbamazepine was degraded and mineralized by self doped NaBiO3 irradiated with visible light.Metastable Bi3+ self-doped NaBiO3 (NBO) nanosheets were prepared by using acidic hydrolysis of NaBiO3·2H2O in HNO3 solutions. It was found that the as-prepared NBO nanosheets showed both chemical oxidation ability and photocatalytic oxidation activity for the degradation of carbamazepine under visible light irradiation. The pseudo-zero order reaction kinetic constant for the photodegradation of carbamazepine (20 mmol L−1) over the metastable NBO nanosheets was 0.087 min−1, being 10.4 and 5.0 times that of the photocatalytic oxidation over the stable NBO nanosheets and the chemical oxidation over the metastable NBO nanosheets in dark, respectively. The enhanced photodegradation of carbamazepine over the metastable NBO nanosheets was mainly attributed to a reaction process of photocorrosion of the NBO nanosheets, which increased generation of singlet oxygen from the lattice oxygen of NBO and promoted a synergistic effect between the chemical oxidation and the photocatalytic oxidation. Singlet oxygen and photo-generated holes were identified as the major reactive species for photodegradation of carbamazepine. By a rough estimation, the (dark) chemical oxidation, photocorrosion process and photocatalysis contributed 19.4%, 60% and 20.6% of the total degradation of carbamazepine, respectively. Based on the identification of intermediates by GC– and LC–MS, two degradation pathways of carbamazepine in both chemical oxidation system and photocatalytic system were proposed. The developed dual-reactive-species-based photocatalysis may be a useful technology for the purification of water containing carbamazepine.Download high-res image (180KB)Download full-size image

•Surface carboxylated Cu0/Fe3O4 nanocomposites were successfully prepared.•Cu0/Fe3O4 could activate molecular oxygen toward degradation of chlorophenols.•Cu0/Fe3O4 exhibited highly catalytic activity in a wide pH range from 3.0 to 10.0.•The generation of O2−, H2O2, and OH over Cu0/Fe3O4 was evidenced and tracked.•The activation of O2 was confirmed to be synergistically initiated by Cu0 and Fe3O4.Surface carboxylated Cu0/Fe3O4 nanocomposites were prepared and used as a heterogeneous catalyst for activating molecular oxygen toward degradation of chlorophenols. The use of 1.0 g L−1 Cu0/Fe3O4 composites yielded a nearly complete removal of 4-chlorophenol (4-CP, 0.1 mmol L−1) in 60 min in a wide pH range from 3.0 to 10.0. The pseudo first rate constant (k) for 4-CP degradation at pHinitial 7.0 in the system of Cu0/Fe3O4-Air was 0.073 min−1, being 10.9 and 7.3 times that obtained in the systems of alone Cu0 and Fe3O4 nanoparticles, respectively. The generation of O2−, H2O2, and OH as reactive oxygen species from the catalytic activation of O2 over the Cu0/Fe3O4 composites was evidenced and tracked. The activation of dissolved oxygen was confirmed to be synergistically initiated by the simultaneous use of strongly-interacted Cu0 and Fe3O4 nanoparticles, where the surface carboxyl groups mediated fast reduction of Fe(III) back to Fe(II) in Fe3O4 domains by Cu0 as a reducing agent. The present study not only sheds light on the synergistic effect between bimetal oxides in the environmental catalytic processes, but also provides a facile and efficient chemical method for the oxidative removal of organic pollutants.Download high-res image (156KB)Download full-size image

•Co/N-CNTs was prepared by a calcination-acid treatment method with Co3[Co(CN)6]2 as a precursor.•Co/N-CNTs had excellent adsorption and catalytic performances for PMS activation.•Co/N-CNTs worked in a wide range of operation conditions with a good recyclability.•There was a synergistic effect between adsorption and catalysis on Co/N-CNTs.•The mechanism involved the efficient cycle between Co(II) and Co(Ш).Bifunctional materials having both good catalytic and adsorptive performances are promising in the field of wastewater treatment. Cobalt-encapsulated and nitrogen-doped bamboo-like carbon nanotubes (Co/N-CNTs) were prepared by a simple method of calcination and acid treatment with Co3[Co(CN)6]2 as a precursor. Based on a series of characterization and performance studies, Co/N-CNTs were confirmed to be able to function as both a catalyst and an adsorbent for oxidative degradation of organic pollutants in the presence of peroxymonosulfate (PMS). When rhodamine B was used as a typical dye pollutant, it was found that all the added pollutant (10 mg L−1) was completely removed in 7 min by using 0.1 g L−1 Co/N-CNTs and 0.2 g L−1 PMS. The fast and efficient degradation of the pollutant was attributed to the synergistic effect between adsorption and catalysis on the surface of Co/N-CNTs. It was confirmed that this bifunctional material provided good performances in a wide range of operation conditions, such as a wide temperature range and a wide pH range. Co/N-CNTs also exhibited a good recyclability. A mechanism study indicated that the main active species in the catalytic oxidation process was surface-bound SO4− and OH.Download high-res image (278KB)Download full-size image

The determination of antibiotics in biological samples is compromised by their interaction with proteins. It is showed here that the water resistant zeolite imidazolate framework 67 (ZIF-67) represents a useful sorbent for solid-phase extraction (SPE) of fluoroquinolones (FQs) from biological samples. ZIF-67 is unique in possessing permanent nanoscale porosity and a high surface area. As a result, it efficiently excludes proteins from the inner network but can well adsorb small organic molecules. Its extraction capacity for FQs exceeds that of isostructural ZIF-8, probably due to high affinity for Co(II) ions in ZIF-67. The findings were exploited to design a method for the analysis of FQs, which were extracted from bio-samples by ZIF-67 via SPE. Following elution of the absorbed FQs with NaOH/methanol, they were quantified by HPLC with diode array detection. The assay has a wide linear range that extends from 3.9 to 4000 μg⋅kg‾1, with detection limits between 1.2 and 2.9 μg⋅kg‾1. The method was successfully applied to the determination of FQs in manure.

It is challenging to fabricate a surface-enhanced Raman scattering (SERS) substrate for capturing targets that have weak affinity with conventional SERS substrates. Hence a new strategy is proposed by combining surface modification and gelation of Ag nanoparticles. The weak affinity between the target and the Ag nanoparticles was strengthened by β-cyclodextrin (CD) as a “bridge”, and the hydrogel structure ensured the good reproducibility and sensitivity of the substrate. In the synthesis, the CD was used as a reducing and shape-controlling agent to form CD-modified Ag nanoparticles, which were then encapsulated into a polyvinyl alcohol (PVA) hydrogel. The three dimensional self-standing PVA–CD–Ag hydrogel showed not only excellent homogeneity and reproducibility in SERS sensing, but also good recognition ability toward sulfonamides. The CD modification strengthened the affinity of sulfonamides to the Ag surface not only through a host–guest interaction drawing sulfonamides into its interior cavity, but also as a scaffold to pull analytes close to its cavity, as clarified by fluorescence and 1H NMR methods. This molecular targeting substrate was used for the trace detection of sulfonamides on a portable Raman instrument, producing detection limits as low as 10 ng mL−1. The new substrate was also used for the identification of sulfonamides from their mixture by providing their fingerprint information.

●A HPLC-CAD method was developed for the determination of perfluorinated carboxylic acids.●The new method showed high recovery, reproducibility and excellent sensitivity.●The new method provided a wide linear range of 5–1000 μg L−1 PFCAs.●The detection limits of the method were 75–220 ng L−1 PFCAs after a preconcentration treatment.●The SPE-HPLC-CAD method was successfully applied to analyze practical wastewater samples.Perfluorocarboxylic acids (PFCAs) are persistent pollutants being widely detected in the environment. In order to quantitatively determine PFCAs, a simple and rapid method for the simultaneous determination of five PFCAs was developed by coupling high performance liquid chromatographic (HPLC) separation and corona-charged aerosol detector (CAD). The PFCAs were separated on a Symmerry® C8 analytical column (150 mm×3.9 mm) under isocratic conditions with a mobile phase consisting of 5 mM ammonium acetate (pH4.9±0.2) and methanol (30:70 (v/v)) at the flow rate 1 mL min−1. Ammonium acetate as ion pairing agent was added to the mobile phase for better separation and peak shapes. The elaborated method was validated for linearity, precision and accuracy. The detection limits ranged from 1.5 to 4.4 μg L−1 for PFCAs with C atoms of C4 to C8, which were decreased further to 75 to 220 ng L−1 after 20-fold preconcentration. The method was confirmed to have good precision with relative standard deviation of 0.9%-4.2% for intraday measurements and 0.9%-4.1% for interday measurements. The optimized method was applied to analyze practical wastewater samples with satisfactory results.

It is a challenge to simultaneously determine the multiple-component targets in complex matrices when some of the targets bear chromophores but some contain no chromophores. A novel HPLC–CAD–DAD method coupled with accelerated solvent extraction and online solid phase extraction (SPE) was developed for simultaneous determination of seven antibiotics in solid bio-matrices. The online SPE operation parameters were optimized on a Acclaim®120 C18 cartridge in terms of extraction efficiency with sample injection volume of 1 mL, and the online SPE operation yielded enhancement factors in the range of 29–77 for the different antibiotics. The proposed method showed good recoveries ranging between 79.2 and 104.7 % for different antibiotics and excellent inter-day and intra-day precision with relative standard deviation values ranging from 0.6 to 7.8 %. The detection limits were between 1.8 and 18.0 μg kg−1.

•Efficient removal of ultralow-level endocrines from water is achieved with graphene adsorption.•Unusual changes were observed in the adsorption isotherms of bisphenols in the tested wide range.•The adsorption decreased the surface grooved regions but increased the flat regions of graphene.•An adsorption mechanisms of bisphenols on graphene was proposed.Graphene was used to remove low-level environmental endocrines in micro-polluted water with the aid of an investigation about the adsorption of bisphenols at low levels in a very wide range from 0.0005 to 70 mg L−1. It was found that over the wide concentration range, the adsorption isotherms could be divided into two regions: they followed the Freundlich model in the lower concentration region (correlation coefficient R2 > 0.99), but obeyed the Langmuir model in the higher concentration region (R2 > 0.99). This was attributed to the adsorption-induced changes in the morphology of graphene, which created different adsorption sites on the surface of graphene. The obtained values of thermodynamic parameters ΔG0, ΔH0 and ΔS0 indicated that the adsorption was a spontaneous, exothermic and entropy-decreasing process. The absolute values of these parameters tended to be decreased with increasing bisphenol concentration, suggesting stronger affinity of the binding sites on graphene for the adsorption of the bisphenols at lower concentrations. As confirmed by some characterization and monitoring experiments, the increased bisphenol adsorption decreased the surface grooved regions formed by wrinkles and increased the flat regions. The highly and lowly-wrinkled (or flat) surface states of graphene accounted for the observed two-stage adsorption isotherms.Download high-res image (208KB)Download full-size image

It is challenging to fabricate a surface-enhanced Raman scattering (SERS) substrate for capturing targets that have weak affinity with conventional SERS substrates. Hence a new strategy is proposed by combining surface modification and gelation of Ag nanoparticles. The weak affinity between the target and the Ag nanoparticles was strengthened by β-cyclodextrin (CD) as a “bridge”, and the hydrogel structure ensured the good reproducibility and sensitivity of the substrate. In the synthesis, the CD was used as a reducing and shape-controlling agent to form CD-modified Ag nanoparticles, which were then encapsulated into a polyvinyl alcohol (PVA) hydrogel. The three dimensional self-standing PVA–CD–Ag hydrogel showed not only excellent homogeneity and reproducibility in SERS sensing, but also good recognition ability toward sulfonamides. The CD modification strengthened the affinity of sulfonamides to the Ag surface not only through a host–guest interaction drawing sulfonamides into its interior cavity, but also as a scaffold to pull analytes close to its cavity, as clarified by fluorescence and 1H NMR methods. This molecular targeting substrate was used for the trace detection of sulfonamides on a portable Raman instrument, producing detection limits as low as 10 ng mL−1. The new substrate was also used for the identification of sulfonamides from their mixture by providing their fingerprint information.