The greater structural versatility of two-dimensional polymeric nanosheets could be available through the development of a bottom-up polymerization strategy compared with top-down nanosheets (such as graphene and metal chalcogenides). However, rational synthesis by solution polymerization has been a long-standing challenge. Considering that Glaser coupling is catalyzed by cuprous (I) salts with the participation of oxygen, an air/liquid interfacial coupling reaction has been designed and used to prepare a two-dimensional porous triptycene-based polymeric nanosheet (2D-PTNS). This 2D-PTNS shows a high BET surface area, good gas adsorption ability and excellent selective adsorption of C2H6/CH4 at ambient temperature and pressure.

•Higher catalytic capacity of Cu/SiC is obtained than Cu/ATP under MW induction.•Active species came from dehydration of Cu clusters and Cu-redox cycle in Cu/ATP.•“Hot spots” sped up the movement of electrons in Cu/SiC to generate h+/e− pairs.•Complete removal of PNP in soil can be achieved with MW catalytic treatment.•The denitro-hydroxylation of PNP is the initial step based on DFT calculations.The catalytic capabilities of copper doped attapulgite (Cu/ATP) and silicon carbide (Cu/SiC) nanocomposites for p-nitrophenol (PNP) were characterized under microwave (MW) irradiation. Higher catalytic performance of Cu/SiC was obtained than that of Cu/ATP due to higher production rate of reactive oxygen species (ROS) as well as higher MW absorptivity. The electron (e−) – hole (h+) pairs were related to the generation of ROS on Cu/SiC. The modification Cu with SiC had an enhancement on the band gap and large EVB absolute values, which promoted the catalytic activity of Cu/SiC. An ROS-producing copper-redox cycle between CuI and CuII of Cu/ATP was responsible for PNP degradation. The produced CuI via thermal dissociation of [Cu–O–Cu]n species in Cu/ATP activated molecular oxygen, followed by Fenton-like reactions to produce ROS. The reusability of the catalysts and negligible phase transformation of Cu species after five rounds of cycle verified the catalyst stability. Based on Density functional theory (DFT) calculation and catalytic experimental analyses, the denitro-hydroxylation of PNP was the initial oxidation reaction step followed by further oxidation to form short-chain carboxylic acids. OH oxidation was predominant whereas O2− was not involved in the OH addition on the meta-position due to lower oxidation energy than the corresponding activation energies. Other than reactive species attack, the “hot spots” on the surface of Cu/SiC was responsible for thermal stabilization of PNP/intermediates in soil. In this study, MW-assisted Cu/ATP and Cu/SiC catalytic degradation of PNP was proved to be an efficient technology for wastewater treatment and soil remediation.

•Higher catalytic performance of Fe/SiC for NOR is obtained under MW induction.•Molecular oxygen is activated by solid Fe0 and FeII on Fe/SiC with MW irradiation.•Fe shell corrosion and subsequent Fe0/II oxidation contribute to ROS generation.•The piperazinyl ring as the most reactive site is directly attacked by OH.Sustained molecular oxygen activation by iron doped silicon carbide (Fe/SiC) was investigated under microwave (MW) irradiation. The catalytic performance of Fe/SiC for norfloxacin (NOR) degradation was also studied. Rapid mineralization in neutral solution was observed with a pseudo-first-order rate constant of 0.2239 min−1 under 540 W of MW irradiation for 20 min. Increasing Fe/SiC rod and MW power significantly enhanced the degradation and mineralization rate with higher yield of reactive oxygen species (ROS). Fe shell corrosion and subsequent Fe0/II oxidation by molecular oxygen with MW activation was the key factor for NOR degradation through two-electron-transfer by Fe0 under acidic conditions and single-electron-transfer by FeII under neutral-alkaline solution. Removal rate of NOR was significantly affected by solution pH, showing higher degradation rates at both acidic and alkaline conditions. The highest removal efficiencies and rates at alkaline pH values were ascribed to the contribution of bound FeII species on the Fe shell surface due to the hydroxylation of Fe/SiC. ·OH was the main oxidizing specie for NOR degradation, confirmed by density functional theory (DFT) calculations and radical scavenger tests. DFT calculations were conducted on the reaction/activation energies of the transition/final states of NOR/degradation products, combined with intermediate identification with high performance liquid chromatography coupled with a triple-quadruple mass spectrometer (HPLC-MS/MS), the piperazinyl ring was the most reactive site for ·OH attack, followed by further ring-opening and stepwise oxidation. In this study, Fe/SiC were proved to be an excellent catalyst for the treatment of fluoroquinolone antibiotics with MW activation.Download high-res image (242KB)Download full-size image

•Effect of EDTA and EDDS addition to ZVI/Air system on degradation of 2,4-DCP was investigated.•Effective removal of 2,4-DCP in contaminated soil was achieved by the heterogeneous ZVI/EDTA/Air (ZEA) system.•O2−/HO2 was the main reactive oxygen species in ZEA system.•Pathways for 2,4-DCP and EDTA degradation by the ZEA system were proposed.The removal of 2,4-dichlorophenol (2,4-DCP) from contaminated soil by an amino carboxylic acid-enhanced zero-valent iron/Air (ZVI/Air) Fenton-like system has been performed in this study. The effects of ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N,N′-disuccinic acid (EDDS) on the catalytic degradation of 2,4-DCP were primarily studied in the presence of ZVI catalyst and O2 oxidant. The result indicated that the degradation of 2,4-DCP in ZVI/Air system was hindered by EDDS but enhanced by EDTA. Complete destruction of 2,4-DCP in contaminated soil was achieved in the heterogeneous ZVI/EDTA/Air (ZEA) Fenton-like system under ambient air and room temperature. ZVI and EDTA were the predominant factors influencing the degradation of 2,4-DCP. The degradation of 2,4-DCP was ascribed to heterogeneous catalytic reaction over the ZVI surface in situ modified by EDTA via the formation of monodentate inner-sphere complexes. In this system, two main reactive oxygen species of O2−/HO2 and Fe(IV) were generated, in which O2−/HO2 was predominant. The novel ZEA oxidation system provides a promising eco-friendly alternative for the remediation of contaminated soils.Graphical abstract

A novel and simple analytical method for the determination of chlorobenzenes (CBs) in soil samples was developed using ultrasonic-assisted water extraction (UAWE) coupled with solvent bar microextraction (SBME). Four chlorobenzenes, 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), hexachlorobenzene (HCB), and 1-chloro-4-nitrobenzene (1-C-4-NB), were used as model compounds to investigate the extraction performance. Parameters affecting the extraction efficiency were investigated in detail. UAWE was used for the extraction of CBs from 1.0 g of sediment using 10 mL of ultrapure water at 100 W for 30 min at 30–35 °C. The extract was subsequently subjected to a single step SBME cleanup and enrichment procedure. Both ends of the solvent bar with about 4 μL of 1-octanol were sealed by a sealing machine, and it was placed in the soil slurry for extraction. After extraction, analysis was carried out by gas chromatography–ion trap mass spectrometry (GC–ITMS) detection. The relative recoveries from the spiked soil sample varied between 93 and 105% for CBs, and exceeded levels achieved for conventional Soxhlet extraction. The method linearities were 10–150, 40–600, and 100–1500 ng g−1 for different CBs. The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.7–27.3 ng g−1 and 2.2–90.9 ng g−1, respectively. Good reproducibilities were obtained with relative standard deviation (RSD) values below 6.8%. The analytical potential of the method was demonstrated by applying the method to spiked soil sample.Highlights► A novel method was developed for the determination of chlorobenzenes in soils. ► Ultrasonic-assisted water extraction was followed by solvent bar microextraction. ► Analysis was carried out by gas chromatography–ion trap mass spectrometry. ► Parameters affecting the extraction efficiency were investigated in detail. ► The technique for the preparation of solvent bar was modified.

Two environmentally friendly sample preparation methods, subcritical water extraction (SWE) and microwave-assisted water extraction (MAWE) coupled to the gas chromatography with electron capture detector (GC-ECD), were evaluated and optimized for the sensitive, selective and solvent-free determination of four chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 4-chlorophenol and pentachlorophenol) in polluted Ya-Er Lake sediments. An orthogonal array design L9 (33) was applied to select the optimum conditions for SWE. The best results as regards sensitivity, repeatability and analyte recovery were obtained using SWE with 9 mL of sodium hydroxide solution (pH 9), at 150 °C for 80 min. The best extraction conditions for MAWE were obtained by using the same extractant as SWE at 900 W and 0.2 MPa for 6 min. Under final working conditions, satisfactory recoveries of individual chlorophenols (CPs) were obtained in the range of 77.7–113.0% and 83.5–104.7% for SWE and MAWE respectively. The effectiveness of the extraction conditions proposed in both methods was evaluated for the extraction of 2,4-DCP in lake sediments with different sample characteristics such as organic carbon and water content. The results indicated that sediments containing relatively low amounts of organic carbon can be quantitatively extracted by both extraction methods. For sediments with larger amounts of organic carbon, the MAWE-based method showed a little better result for analyte recovery than SWE.

•The long-term stability of the FeSO4-H2SO4 treated COPR was evaluated.•Reliable long-term stability for samples curing 400 days was achieved.•H2SO4 significantly enhanced the stabilization efficiency of COPR using FeSO4.•H+ and SO42− both reinforced Cr(VI) release from COPR core to react with Fe(II).In this study, the long-term stability of Cr(VI) in the FeSO4 and H2SO4 (FeSO4-H2SO4) treated chromite ore processing residue (COPR) after 400 curing days and the stabilization mechanisms were investigated. FeSO4-H2SO4 treatment significantly reduced toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) Cr(VI) concentrations to lower than the regulatory limit of 1.5 mg L−1 (HJ/T 301-2007, China EPA) even for the samples curing 400 days, achieving an outstanding long-term stability. Our independent leaching tests revealed that H+ and SO42− have synergistic effect on promoting the release of Cr(VI), which would make Cr(VI) easier accessed by Fe(II) during stabilization. The contributions of H+ and SO42− to Cr(VI) release ratio were 25%–44% and 19%–38%, respectively, as 5 mol H2SO4 per kg COPR was used. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and alkaline digestion analyses were also employed to interpret the possible stabilization mechanism. Cr(VI) released from COPR solid was reduced to Cr(III) by Fe(II), and then formed stable FexCr(1−x)(OH)3 precipitate. This study provides a facile and reliable scheme for COPR stabilization, and verifies the excellent long-term stability of the FeSO4-H2SO4 treated COPR.Download high-res image (253KB)Download full-size image

Two environmentally friendly sample preparation methods, subcritical water extraction (SWE) and microwave-assisted water extraction (MAWE) coupled to the gas chromatography with electron capture detector (GC-ECD), were evaluated and optimized for the sensitive, selective and solvent-free determination of four chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 4-chlorophenol and pentachlorophenol) in polluted Ya-Er Lake sediments. An orthogonal array design L9 (33) was applied to select the optimum conditions for SWE. The best results as regards sensitivity, repeatability and analyte recovery were obtained using SWE with 9 mL of sodium hydroxide solution (pH 9), at 150 °C for 80 min. The best extraction conditions for MAWE were obtained by using the same extractant as SWE at 900 W and 0.2 MPa for 6 min. Under final working conditions, satisfactory recoveries of individual chlorophenols (CPs) were obtained in the range of 77.7–113.0% and 83.5–104.7% for SWE and MAWE respectively. The effectiveness of the extraction conditions proposed in both methods was evaluated for the extraction of 2,4-DCP in lake sediments with different sample characteristics such as organic carbon and water content. The results indicated that sediments containing relatively low amounts of organic carbon can be quantitatively extracted by both extraction methods. For sediments with larger amounts of organic carbon, the MAWE-based method showed a little better result for analyte recovery than SWE.