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A label-free electrochemical sensor, based on a classic lead ions (Pb 2+ )-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 Pb 2+ . 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 Pb 2+ -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 Pb 2+ , 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 Pb 2+ 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 Pb 2+ 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 Pb 2+ in drinking water defined by the U.S. Environmental Protection Agency. The electrochemical sensor was also used to detect Pb 2+ 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 Pb 2+ in aqueous environment., (Copyright © 2016 Elsevier B.V. All rights reserved.)

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 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. [ABSTRACT FROM AUTHOR]

In this study, a novel nitrogen-functionalized magnetic ordered mesoporous carbon (N-Fe/OMC) with uniform pore size (3.8 nm) and excellent magnetic property (8.46 emu/g) was fabricated through simple impregnation then polymerization and calcination. The resultant adsorbent exhibited more preferential sorption toward Pb(II) and phenol than simple equivalent mixture of magnetic ordered mesoporous carbon (Fe/OMC) and pristine ordered mesoporous carbon (OMC). Binary adsorption showed that the coexistence of Pb(II) and phenol at low concentrations would slightly accelerate their jointly adsorption because of partial complexation between Pb(II) and phenol. While at high concentrations, Pb(II) adsorption would be inhibited in relation to the competition from phenol, but phenol adsorption was scarcely affected due to the directly phenol molecular adsorption pattern. Pb(II) adsorption was more suitable in alkaline solution and affected by ionic strength on account of electrostatic interaction, whereas phenol adsorption was better in neutral pH and hardly interfered by ionic strength as the adsorption was a physical combination process. Thermodynamics indicated that the uptakes of Pb(II) and phenol were endothermic and exothermic processes, respectively. Moreover, N-Fe/OMC could be regenerated effectively and recycled by using dilute NaOH and acetone solutions. These superior properties demonstrate that N-Fe/OMC is attractive for practical applications in treatment of water contamination by Pb(II) and phenol. [ABSTRACT FROM AUTHOR]

• BMC was synthesized and applied as a novel adsorbent. • BMC exhibited higher adsorption capacity than the pristine OMC. • Several kinetic and isotherm models were applied to interpret the adsorption process. • A possible adsorption mechanism was proposed. • BMC showed stable adsorption performance in the natural water and good reusability. Boron doped ordered mesoporous carbon (BMC) was prepared to improve the adsorption of Pb(II). The effects of several parameters such as contact time, pH, and ionic strength on the adsorption by both pristine ordered mesoporous carbon (OMC) and BMC were investigated. Thermodynamic, sorption isotherm and adsorption kinetics models were used to study the adsorption mechanisms by each of the adsorbents. Based on intraparticle diffusion model, the adsorption process by the two adsorbents mainly involved the quick liquid-film diffusion stage and slow pore diffusion portion, and fitting experimental data with Temkin model indicates that the adsorption process by both of the adsorbents involve physisorption and chemisorption. Based on Langmuir model, the estimated maximum adsorption capacity for BMC was about 1.3 times higher than the pristine OMC. Moreover, BMC retained good adsorption performance in tap and lake water, and could be regenerated effectively and recycled using EDTA. The results suggested that BMC, with enhanced adsorption performance compared with OMC, could be considered as very effective and promising materials for Pb (II) removal from wastewater. [ABSTRACT FROM AUTHOR]