Enhanced Cr (VI) removal with Pb (II) presence by Fe2+-activated persulfate and zero-valent iron system.

Combined heavy metals such as chromium (Cr (VI)) and lead (Pb (II)) in natural water have globally posed severe environmental and public health risk. Here the removal of Cr (VI) and Pb (II) mixed pollutants using Fe2+-activated persulfate (PS) with extra zero-valent iron (ZVI), which was not only a supplementary Fe2+ source, but also a high-efficiency absorbent, was investigated. During removal, pivotal factors of initial pollutant concentration, dosages of ZVI and PS, initial pH and temperatures were examined. Interestingly, generating a lot of H+ in the process of Fe (II) activating persulfate were helpful to the corrosion of ZVI over a large range of pH (1-9). Under the optimum condition, removal efficiency of Pb (II) and Cr (VI) have reached 100% and 94.26% respectively. The removal mechanism was suggested as a three-step reaction that the Pb (II) boosted the removal of Cr (VI) by co-precipitated in wastewater, and the Pb (II) and Cr (VI) were adsorbed and subsequently reduced to Pb0 and Cr3+ as Cr(OH)3 or Cr3+-Fe3+ hydroxides on ZVI surface. Cr (VI) and Pb (II) adsorption kinetics agreed with the pseudo-second-order reaction rate expression. In addition, we were surprised to found that the contribution effect of chromium and lead co-precipitation for their removal by Fe (II) - PS-ZVI has strong dependence on initial pH and concentration ratio of Cr (VI) and Pb (II). The result indicated that Fe (II)-PS-ZVI system should be a favourable removal technology for Cr (VI) and Pb (II).

FBCU-Net: A fine-grained context modeling network using boundary semantic features for medical image segmentation.

The performance of deep learning-based medical image segmentation methods largely depends on the segmentation accuracy of tissue boundaries. However, since the boundary region is at the junction of areas of different categories, the pixels located at the boundary inevitably carry features belonging to other classes and difficult to distinguish. This paper proposes a fine-grained contextual modeling network for medical image segmentation based on boundary semantic features, FBCU-Net, which uses the semantic features of boundary regions to reduce the influence of irrelevant features on boundary pixels. First, based on the discovery that indistinguishable pixels are usually boundary pixels in medical images, we introduce new supervision information to find and classify boundary pixels. Second, based on the existing relational context modeling schemes, we generate the boundary region representations representing the semantic features of boundary regions. Last, we use boundary region representations to reduce the influence of irrelevant features on boundary pixels and generate highly discriminative pixel representations. Furthermore, to enhance the attention of the network to the boundary region, we also propose the boundary enhancement strategy. We evaluate the proposed model on five datasets, TUI (Thyroid Tumor), ISIC-2018 (Dermoscopy), 2018 Data Science Bowl (Cell Nuclei), Glas (Colon Cancer), and BUSI (Breast Cancer). The results show that FBCU-Net has better boundary segmentation performance and overall performance for different medical images than other state-of-the-art (SOTA) methods, and has great potential for clinical application.

Pivotal effects of external Fe2+ on remediation of arsenite by zero-valent iron/persulfate: Efficiencies and mechanism.

Persulfate could be activated by zero-valent iron (ZVI) leading to the rapid removal of various contaminants. However, quick consumption of Fe2+ largely constrained the removal (%) of target pollutants. Here it was reported that Na2S2O8 (SP) combined with ZVI, as an external source of Fe2+, was activated by Fe2+ to quickly (minutes scale) and efficiently (more than 90%) remove As (III) from aqueous solution at an initial pH value from 1.0 to 9.0. As (III) removal was obviously improved by an increase of Fe2+ rather than Na2S2O8 dosage. The removal of As (III) using Fe2+-SP-ZVI system followed the pseudo-second-order kinetic and pseudo-first-order kinetic expression. Fe2+ from ZVI oxidization could improve the efficient generation of , which obviously boosted ZVI corrosion. The production of could be manipulated by oxalic acid, ethylenediaminetetraacetic acid (EDTA), citric acid and phosphates through controlling the concentration of dissociative Fe2+, leading to an obvious repression on As (III) removal. The fitting of X-ray absorption fine structure (XAFS) spectra illustrated that the interatomic distance of As-O shell was located between As(III)-O and As(V)-O shell and external Fe2+ could promote the oxidation of As (III) to As (V) from 35.6% in 1.0 min-44.5% in 10.0 min. Goethite as the main component of iron oxyhydroxides might play a significant role of As (III) adsorption in Fe2+-SP-ZVI system. These findings are crucial for knowing the fate and transport of arsenic under permeable reactive barriers.

Involute the reactivity of persulfate with zero-valent iron for enhanced removal of arsenic (V) in aspect involvement of Fe2+ or Fe3.

Being a fundamental issue regarding sewage treatment, heavy metals removal from industrial effluents has been subject to intense scrutiny in both the academic and practical worlds. The removal of pentavalent arsenic (As(V)), one of the most poisonous pollutants, was investigated using a sodium persulfate and iron powder system activated by ferrous ions (Fe2+-ZVI-PS). As(V) could be effectively removed by an Fe2+-ZVI-PS system in a timely fashion (minute scale) with high removal rates (more than 90.0%) over a wide range of pH (1-9) and concentration (20-100 mg/L). The removal of As(V) by the Fe2+-ZVI-PS system integrated favorably with the pseudo-second-order reaction kinetics. Researches on X-ray photoelectron spectroscopy (XPS) demonstrated that the Fe2+-ZVI-PS system enables the removal of As(V) through the process of co-precipitation and adsorption. Our findings thus emphasized that the Fe2+-ZVI-PS system should be an effective trigger to purifying arsenic from the environment. Our results indicated that the Fe2+-ZVI-PS system could be an effective candidate for remediation of arsenic in the environment.