Ya Pang

Immobilization of laccase on magnetic bimodal mesoporous carbon and the application in the removal of phenolic compounds.

A novel magnetically separable laccase immobilized system was constructed by adsorbing laccase into bimodal carbon-based mesoporous magnetic composites (CMMC). A large adsorption capacity (491.7 mg g(-1)), excellent activity recovery (91.0%) and broader pH and temperature profiles than free laccase have been exhibited by the immobilized laccase. Thermal stability was enhanced to a great extent and operational stability was increased to a certain extent. The shift of kinetic parameters indicated affinity change between enzyme and substrate. Application of the immobilized system in phenol and p-chlorophenol removal was investigated in a batch system. Adsorption effects of the support were responsible for the quick removal rate in the first hour, and up to 78% and 84% of phenol and p-chlorophenol were removed in the end of the reaction, respectively, indicating that the magnetic bimodal mesoporous carbon is a promising carrier for both immobilization of laccase and further application in phenol removal.

Insight into highly efficient co-removal of p-nitrophenol and lead by nitrogen-functionalized magnetic ordered mesoporous carbon: Performance and modelling

Highly efficient simultaneous removal of Pb(II) and p-nitrophenol (PNP) contamination from water was accomplished by nitrogen-functionalized magnetic ordered mesoporous carbon (N-Fe/OMC). The mutual effects and inner mechanisms of their adsorption onto N-Fe/OMC were systematically investigated by sole and binary systems, and thermodynamic, sorption isotherm and adsorption kinetics models. The liquid-film diffusion step might be the rate-limiting step for PNP and Pb(II). The fitting of experimental data with Temkin model indicates that the adsorption process of PNP and Pb(II) involve physisorption and chemisorption. There exist site competition and enhancement of PNP and Pb(II) on the sorption to N-Fe/OMC. Moreover, N-Fe/OMC could be regenerated effectively and recycled by using dilute NaOH and acetone. These demonstrated superior properties of N-Fe/OMC indicate that it could be applied to treatment of wastewaters containing both lead and PNP.

Highly effective adsorption of cationic and anionic dyes on magnetic Fe/Ni nanoparticles doped bimodal mesoporous carbon.

Magnetic Fe/Ni nanoparticles doped bimodal mesoporous carbon (MBMC) was prepared for highly effective adsorption of cationic dye methylene blue (MB) and anionic dye methyl orange (MO). Structure characterization demonstrated that Fe/Ni nanoparticles were embedded into the interior of the mesoprous carbon, and MBMC maintained ordered and bimodal mesopores. The effects of several parameters such as contact time, pH, temperature, ionic strength and dye molecular structure on the adsorption were investigated. Alkaline pH was better for MB adsorption, while acidic pH was more favorable for MO uptake. The adsorption capacity was slightly enhanced when existing ion concentrations increased. Adsorption on MBMC was affected by the molecular structures of different dyes, and both primary and secondary pores of MBMC were involved in dye adsorption. The adsorption kinetics fitted well with pseudo-second-order model and exhibited 3-stage intraparticle diffusion mode. Equilibrium data were best described by Langmuir model, and the estimated maximum adsorption capacity for MB and MO was 959.5mg/g and 849.3mg/g, respectively. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Moreover, the adsorbent could be regenerated using ethanol, and the regenerated adsorbent after seven cycles could retain over 80% of the adsorption capacity for the fresh adsorbent. The results suggested that MBMC could be considered as very effective and promising materials for both anionic and cationic dyes removal from wastewater.

Cr(VI) reduction by Pseudomonas aeruginosa immobilized in a polyvinyl alcohol/sodium alginate matrix containing multi-walled carbon nanotubes.

Pseudomonas aeruginosa (P. aeruginosa) was immobilized with polyvinyl alcohol (PVA), sodium alginate and multiwalled carbon nanotubes (MCNTs). After immobilization, the beads were subjected to freeze-thawing to enhance mechanical strength. When exposed to 80 mg/L Cr(VI), the immobilized bacteria were able to reduce 50% of them in 84 h, however the free cells were deactivated at this concentration. The beads were used to reduce 50 mg/L Cr(VI) for nine times, with the reduction efficiency above 90% in the first five times and 65% in the end.

Trace detection of picloram using an electrochemical immunosensor based on three-dimensional gold nanoclusters

Picloram, a herbicide widely used for broadleaf weed control, is persistent and mobile in soil and water with adverse health and environmental effects. It is important to develop a sensitive method for accurate detection of trace picloram in the environment. In this article, a type of ordered three-dimensional (3D) gold (Au) nanoclusters obtained by two-step electrodeposition using the spatial obstruction/direction of the polycarbonate membrane is reported. Bovine serum albumin (BSA)-picloram was immobilized on the 3D Au nanoclusters by self-assembly, and then competitive immunoreaction with picloram antibody and target picloram was executed. The horseradish peroxidase (HRP)-labeled secondary antibody was applied for enzyme-amplified amperometric measurement. The electrodeposited Au nanoclusters built direct electrical contact and immobilization interface with protein molecules without postmodification and positioning. Under the optimal conditions, the linear range for picloram determination was 0.001-10 μg/ml with a correlation coefficient of 0.996. The detection and quantification limits were 5.0 × 10(-4) and 0.0021 μg/ml, respectively. Picloram concentrations in peach and excess sludge supernatant extracts were tested by the proposed immunosensor, which exhibited good precision, sensitivity, selectivity, and storage stability.

Removal and recovery of Zn2+ and Pb2+ by imine-functionalized magnetic nanoparticles with tunable selectivity.

This research investigated the adsorption of zinc and lead from binary metal solution with tunable selectivity. A nano adsorbent was prepared by introducing imine groups onto the surface of stability enhanced magnetic nanoparticles and then characterized by TEM and FTIR. Binary metal components adsorption was carried out in different concentration of metal and EDTA solution. Due to the interaction between metals and adsorbent in the presence of EDTA, the selective adsorption of zinc and lead could be achieved with 100% selectivity. To only remove zinc from binary metals, the solution condition was [EDTA]/[M(2+)] = 0.7 with pH of 6, and its saturated adsorption capacity was 1.25 mmol/g. For selective adsorption of lead, an equilibrium adsorption capacity of 0.81 mmol/g was obtained under the condition of [EDTA]/[M(2+)] = 0.7 and pH of 2. The exhausted adsorbent could be regenerated by simple acid or alkali wash, and high purity lead and zinc salt solutions were recovered and concentrated.

Highly sensitive fluorescence quantification of picloram using immunorecognition liposome

Picloram is a widely used chlorinated herbicide, which is quite persistent and mobile in soil and water with adverse health and environmental risks. A simple and efficient method with high sensitivity and good selectivity was developed in this work to analyze picloram. The aldehyde group functionalized quartz glass plate was used to catch picloram by Schiff base reaction, and reacted with the liposomes-labeled antibody. The fluorescein isothiocyanate (FITC) solution was encapsulated in the liposomes. After being released from the liposomes, the fluorescence of FITC was measured by a fluorimeter. It was found that the fluorescence intensity is linearly correlated to the logarithm of picloram concentration, ranging from 1.0 × 10(-4) to 100 ng mL(-1), with a detection limit of 1.0 × 10(-5) ng mL(-1). Picloram concentration in real wastewater samples were accurately measured by the proposed method and HPLC, the results of the two methods were approximately the same. The proposed method showed high sensitivity and good selectivity, and could be an efficient tool for picloram quantitative analysis.

Plasmonic resonance excited dual Z-scheme BiVO4/Ag/Cu2O nanocomposite: synthesis and mechanism for enhanced photocatalytic performance in recalcitrant antibiotic degradation

The utilization of solar energy based on semiconductor photocatalysts for pollutant removal and environmental remediation has become a research hot spot and attracted great attention. In this study, a novel ternary BiVO4/Ag/Cu2O nanocomposite has been successfully synthesized via simple wet impregnation of Cu2O particles coupled with a subsequent photo-reduction pathway for the deposition of metallic Ag on the surface of BiVO4. The resulting BiVO4/Ag/Cu2O photocatalyst was used for the degradation of tetracycline (TC) under visible light irradiation (λ > 420 nm). Results showed that the coating contents of the Cu2O and Ag particles presented a great effect on the eventual photocatalytic activity of the photocatalysts, and the optimum coating contents of Cu2O and Ag were obtained with their mass ratios of 3% and 2%, respectively. Under optimum conditions, nearly 91.22% TC removal efficiency was obtained based on ternary BiVO4/Ag/Cu2O nanocomposites, higher than that of pure BiVO4 (42.9%) and binary BiVO4/Cu2O (65.17%) and BiVO4/Ag (72.63%) nanocomposites. Meanwhile, the enhanced total organic carbon (TOC) removal efficiency also indicated the excellent photocatalytic degradation ability of the BiVO4/Ag/Cu2O nanocomposites. As for their practical application, the effects of initial TC concentration, various supporting electrolytes and different irradiation conditions were investigated in detail. Three-dimensional excitation–emission matrix fluorescence spectroscopy (3D EEMs) was used to show the by-products of TC molecule degradation. Cycling experiments indicated the high stability of the as-prepared photocatalysts. Furthermore, the results obtained from radical trapping experiments and ESR measurements suggested that the photocatalytic degradation of TC in the BiVO4/Ag/Cu2O based photocatalytic system was the joint action of the photogenerated holes (h+), superoxide radical (˙O2−) and hydroxyl radical (˙OH). The enhanced photocatalytic activity of BiVO4/Ag/Cu2O was attributed to the synergistic effect of Cu2O, Ag and BiVO4, especially the surface plasmon resonance effect and the established local electric field brought about by metallic Ag. Additionally, to deeply understand the reaction mechanism, a dual Z-scheme charge transfer pathway has been proposed.

A label–free GR–5DNAzyme sensor for lead ions detection based on nanoporous gold and anionic intercalator

A label-free electrochemical sensor, based on a classic lead ions (Pb2+)-dependent GR-5DNAzyme as the catalytic unit, disodium-anthraquinone-2,6-disulfonate (AQDS) as DNA intercalator, and nanoporous gold (NPG) for signal amplification, was designed for sensitive and selective detection of Pb2+. Firstly, NPG modified electrode surface were employed as a platform for the immobilization of thiolated probe DNA, and then, hybridized with DNAzyme catalytic beacons. The Pb2+-induced catalytic reaction makes the substrate strand break at the cleavage sitGe irreversibly, which disturbs the formation of DNA strands. AQDS served as an indicator that intercalated into the base-pairing regions of DNAzyme, resulting in a strong electrochemical signal. In the presence of Pb2+, the complementary regions were reduced, due to the fracture of the DNA strand, resulting in the release of AQDS. And a decreased current was obtained, corresponding to Pb2+ concentration. Taking advantage of the amplification effect of NPG electrode for increasing the reaction sites of thiol modified capture probe, the proposed electrochemical biosensor could detect Pb2+ quantitatively, in the range of 1-120nM, with a limit of detection as low as 0.02nM, which is much lower than the maximum contamination level for Pb2+ in drinking water defined by the U.S. Environmental Protection Agency. The electrochemical sensor was also used to detect Pb2+ from real water samples, and the results showed excellent agreement with the values determined by inductively coupled plasma mass spectroscopy. This biosensor showed a promising potential for on-site detecting Pb2+ in aqueous environment.

Sensitive and renewable picloram immunosensor based on paramagnetic immobilisation

Picloram (4-amino-3,5,6-trichloro-2-pyridincarboxylic acid) is one of the chlorinated pesticides. It is widely used for control of wood plants, wheat, barley and wide range of broadleaf weeds as a plant growth regulator. An immunosensor was developed for detection of picloram concentration in compost extracts and river water. The laccase-picloram was prepared. The magnetic core-shell (Fe3O4-SiO2) nanoparticles were modified with anti-picloram-IgG and attached to the surface of carbon paste electrode (CPE) with the aid of paramagnetism. Following competitive immunoreaction with picloram and the picloram-laccase to form immunocomplex, electrochemical measurement was carried out. After immunoassay, the electrode was immersed in glycin-hydrochloric acid buffer or polished with diamond paper for regeneration. The linear range for picloram detection was 1 × 10–4–10 µg mL–1 with the correlation coefficient of 0.9936, and the detection limit is 1 × 10–4 µg mL–1. The laccase labelled on the picloram for competitive immunoassay showed good activity, and the current response was strong and stable in electrochemical detection. The current reached 95% of the steady-state current within about 100 s. The proposed immunosensor exhibited good precision, sensitivity, selectivity, reusability, and storage stability.