Facile fabrication of Fe/Zr binary MOFs for arsenic removal in water: High capacity, fast kinetics and good reusability.

A water-stable bimetallic Fe/Zr metal-organic framework [UiO-66(Fe/Zr)] for exceptional decontamination of arsenic in water was fabricated through a facile one-step strategy. The batch adsorption experiments revealed the excellent performances with ultrafast adsorption kinetics due to the synergistic effects of two functional centers and large surface area (498.33 m2/g). The absorption capacity of UiO-66(Fe/Zr) for arsenate [As(V)] and arsenite [As(III)] reached as high as 204.1 mg/g and 101.7 mg/g, respectively. Langmuir model was suitable to describe the adsorption behaviors of arsenic on UiO-66(Fe/Zr). The fast kinetics (adsorption equilibrium in 30 min, 10 mg/L As) and pseudo-second-order model implied the strong chemisorption between arsenic ions and UiO-66(Fe/Zr), which was further confirmed by DFT theoretical calculations. The results of FT-IR, XPS analysis and TCLP test demonstrated that arsenic was immobilized on the surface of UiO-66(Fe/Zr) through Fe/Zr-O-As bonds, and the leaching rates of the adsorbed As(III) and As(V) from the spent adsorbent were only 5.6% and 1.4%, respectively. UiO-66(Fe/Zr) can be regenerated for five cycles without obvious removal efficiency decrease. The original arsenic (1.0 mg/L) in lake and tap water was effectively removed in 2.0 hr [99.0% of As(III) and 99.8% of As(V)]. The bimetallic UiO-66(Fe/Zr) has great potentials in water deep purification of arsenic with fast kinetics and high capacity.

Identification of mercury species in coal combustion by-products from power plants using thermal desorption-atomic fluorescence spectrometry on-line coupling system.

Along with the environmental protection policies becoming strict in China, the air pollution control devices (especially selective catalytic reduction (SCR)) are widely equipped in coal-fired power plants. The installation and run of these devices will inevitably affect mercury (Hg) species distribution in coal fired by-products such like fly ash (FA) and gypsum. In this work, a new on-line coupling system based on atomic fluorescence spectrometry (AFS) with a home-made chromatographic workstation was successfully developed to identify Hg species through thermal programmed desorption (TPD). The influences of matrix, furnace temperature, and carrier gas flow on analytical performance were investigated and the parameters were optimized. The FA and gypsum samples from coal-fired power plants equipped with SCR were collected and the mercury species were analyzed by the developed coupling system. HgCl2 and HgO were the main species in FA, while Hg2Cl2 and HgO were the main species in gypsum. All of Hg species in the studied FA and gypsum samples were released below 400 °C. A sequential extraction procedure was applied to further verify the operational Hg species including mobile and non-mobile fractions in FA and gypsum samples. This study demonstrated that AFS coupled with TPD procedure was an effective method to analyze Hg species in coal combustion by-products from power plants.

Exceptional removal and immobilization of selenium species by bimetal-organic frameworks.

Binary metallic organic frameworks can always play excellent functions for pollutants removal. One binary MOFs, UiO-66(Fe/Zr)), was newly synthesized and applied to remove aquatic selenite (SeIV) and selenate (SeVI). The adsorption behaviors and mechanisms were investigated using batch experiments, spectroscopic analyses, and theoretical calculations (DFT). The characterization results showed that the material inherited the topological structure of UiO-66 and excellent thermal stability. The large specific surface area (467.52 m2/g) and uniform mesoporous structures of the synthesized MOFs resulted in fast adsorption efficiency and high adsorption capacity for selenium species. The adsorbent kept high adsorption efficiency in a wide pH range from 2 to 11 with good anti-interference ability. The maximum adsorption capacity for Se(IV) and Se(VI) reached as high as 196 mg/g at pH 3 and 258 mg/g at pH 5, respectively. The process was conformed to fit pseudo-second-order kinetics and Langmuir isotherm, and could be explained by the formation of Fe/Zr-O-Se bond on the material surface, which was interpreted by the results of XPS, FTIR and DFT calculation. The regeneration and TCLP experiments demonstrated that UiO-66(Fe/Zr) could be regenerated for five cycles without obvious decrease of efficiencies, and the leaching rate of the adsorbed Se(IV) and Se(VI) in the spent adsorbent were only 4.8% and 2.3%. More than 99% of original Se(IV) and Se(VI) in the lake and tap water samples (1.0 mg/L of Se) could be removed in 2.0 h.

Electrospun metal-organic frameworks hybrid nanofiber membrane for efficient removal of As(III) and As(V) from water.

Metal-organic frameworks (MOFs) have been widely applied for pollutants removal in water. However, the powdered MOFs are always suffered from aggregation during use and difficult collection after use. These problems discount their efficiency and inhibit their reusability. In this work, Zr-based MOF (UiO-66) was successfully imprisoned into a water-stable polyacrylonitrile (PAN) substrate by electrospinning. The containing UiO-66 hybrid membrane was confirmed by instrumental characterizations and its stability was also investigated by ICP-OES analysis. The obtained composite membrane can efficiently remove both arsenite (AsIII) and arsenate (AsV) from water under natural pH conditions. The adsorption kinetic fitted well with pseudo-second-order model and was dominated by chemisorption. Its adsorption isotherm can be described by Langmuir model. The maximal adsorption capacities of the hybrid membrane for As(V) and As(III) were 42.17 mg/g and 32.90 mg/g, respectively. Our results demonstrated that the MOFs-dispersed electrospun nanofiber membrane can greatly inherit the MOFs' original adsorption properties and exhibits good regenerability without loss of MOFs. Electrospinning is an effective and practical method for the preparation of MOFs hybrid membrane, which makes the composite very easy to be collected after use.

Comparison of arsenic fractions and health risks in PM2.5 before and after coal-gas replacement.

Coal-Gas replacement project has been implemented to decrease haze pollution in China in recent years. Airborne arsenic (As) mostly originates from coal burning processes. It is noteworthy to compare the distribution of arsenic fraction in PM2.5 before and after coal-gas replacement. Eighty PM2.5 samples were collected in Baoding in December 2016 (coal dominated year) and December 2017 (gas dominated year) at different functional areas including residential area (RA), industrial area (IA), suburb (SB), roadside (ST) and Botanical Garden Park (BG). The fraction, bioavailability and health risk of As in the PM2.5 samples were investigated and compared between these two years. Arsenic was mainly distributed in the non-specifically sorbed fraction (F1) and the residual fraction (F5). However, the proportion of F1 to the total As in 2017 was higher than that in 2016, while the proportion of As in the amorphous and poorly-crystalline hydrous oxides of Fe and Al fraction (F3) in 2017 was lower. The distributions of fraction and bioavailability showed temporal and spatial characteristics. The total concentration and bioavailability of As in SB and IA were significantly higher than those in RA, ST and BG. The BF (Bioavailability Factor) values of As ranged from 0.30 to 0.61. Health risk assessment indicated that the hazard quotient (HQ) and carcinogenic risk (CR) of As in PM2.5 significantly decreased after coal-gas replacement.

Fraction distribution of arsenic in different-sized atmospheric particulate matters.

The sequential extraction method was used to determine the fraction of arsenic (As) in different-sized particulate matters (PMs) (i.e., PM2.5, PM10, and total suspended particles (TSP)). Samples were collected from Baoding, a typical medium-sized city with the serious haze pollution in China. The bioavailabilities of As in the samples were estimated based on the fraction results. A large percentage of fine particles were detected in TSP, with the average PM2.5/PM10 and PM10/TSP ratios all above 0.69. The total concentrations of As in PM2.5, PM10, and TSP samples were in the range of 4.5-296.4, 14.1-708.0, and 32.8-798.0 ng m-3, respectively. The mass percentages of As in PM2.5, PM2.5-10, and PM10-100 were calculated; the results indicated that As tended to concentrate in fine particles. PM-bound As mainly presented in the nonspecifically sorbed fraction (F1) during all of the sampling periods. The percentages of F1-As and bioavailability of As were higher in PM2.5, followed by PM10 and TSP. By contrast, the residual fraction (F5-As) contents declined in the order of TSP > PM10 > PM2.5. Significant differences in the speciation and bioavailability of As in different-sized PMs were found, and the influence of particle size on the speciation and bioavailability of As in PMs was verified. Fine particles adsorbed more As with higher bioavailability, and potentially led to more serious adverse effects on human health than the larger ones.

A comparative study on arsenic fractions in indoor/outdoor particulate matters: a case in Baoding, China.

The distribution and bioavailability of arsenic (As) in indoor/outdoor total suspended particulates (TSP), inhalable particulate matters (PM10), and fine particulate matters (PM2.5) in Baoding, China were investigated. The average I/O ratios for TSP, PM10, and PM2.5 were 0.52, 0.66, and 0.96, respectively. There was no significant correlation between indoor/outdoor TSP, PM10, and PM2.5. The indoor/outdoor concentrations of As surpassed the limited value of As. I/O ratios of arsenic in TSP, PM10, and PM2.5 were 0.52, 0.58, and 0.55, respectively. The contents of arsenic in different fractions were mainly affected by the total concentrations of arsenic in particulate matters (PM) rather than the particle sizes for TSP and PM10. Arsenic was mainly in non-specifically sorbed fraction (F1) in both indoor and outdoor PM2.5. The evaluated carcinogenic risk (CR) was within the safe level. The bioavailability of As increased with particle size decreasing for both indoor and outdoor PM. The potential bioavailability of As in outdoor particles was higher than that of indoor particles with the same size, especially PM2.5.

Speciation and bioaccessibility of heavy metals in PM2.5 in Baoding city, China.

The health risks and toxicity of heavy metals (HMs) in PM2.5 are not only associated with their total amounts, but also with their species and bioaccessibility. In this study, the speciation (fractions) and bioaccessibility of HMs (Pb, Cd, Cr, Cu and Zn) as well as their correlations in fine particulate matter (PM2.5) samples from four seasons were studied. A sequential extraction procedure was applied to divide the studied HMs into four fractions: acid-soluble fraction (F1), reducible fraction (F2), oxidative fraction (F3) and residual fraction (F4). The simulated body fluids (gastrointestinal and lung phases) were used for in vitro tests in order to evaluate the bioaccessibility of HMs. The distribution of HMs in PM2.5 was season and element dependent. It was found that Zn was the most abundant element among the five measured metals and followed by Pb, Cu, Cr and Cd. The total contents of each HM in different seasons were in the following order: winter > autumn > spring > summer. The studied HMs were mainly concentrated in acid-soluble fraction (F1) with high bioaccessibility (p < 0.05) except for Cr. Zn, Pb and Cu possessed the highest bioaccessibility in summer while Cd and Cr were the highest in winter. In vitro tests indicated that HMs in PM2.5 were much more accessible to gastrointestinal fluids rather than lung phase (Gamble's solution). A significant correlation was found between the results from the optimized BCR sequential extraction and solubility bioaccessibility research consortium (SBRC). The fractions extracted by SBRC were consistent with the first two fractions extracted by the sequential extraction method.

A meta-analysis of interleukin-6 as a valid and accurate index in diagnosing early neonatal sepsis.

We aimed to systematically assess the overall value of interleukin 6 (IL-6) in diagnosing neonates with sepsis. A systematic literature search was conducted using the following electronic databases: PubMed, Embase, and Cochrane, to identify eligible studies through the index words updated till November 2018. Cross-sectional studies, as well as prospective cohort studies, were included in the above-mentioned group of eligible studies. We also searched the literature sources that had a link to the present study, which were further assessed by heterogeneity through the use of a proper-effects model to calculate pooled weighted specificity, sensitivity, and diagnostic odds ratio (DOR). We also conducted summary receiver operating characteristic (SROC) analyses for neonatal sepsis. In the present meta-analysis, there were 31 studies exploring IL-6 for the diagnostic accuracy of neonatal sepsis. The global specificity and sensitivity of IL-6 for neonatal sepsis were as follows: 88% (95% confidence interval [CI]: 83%-92%) and 82% (95% CI: 77%-86%), respectively. The global positive and negative likelihood ratio of IL-6 in diagnosing neonatal sepsis were 7.03 (95% CI: 4.81-10.26) and 0.20 (95% CI: 0.15-0.26), respectively. The global DOR was 29.54 (95%CI: 18.56-47.04) of IL-6. In addition, the area under the SROC was high for IL-6 (AUC = 0.92; 95% CI: 0.89-0.94). In this study, we performed a systematic review and meta-analysis to assess the diagnostic accuracy studies of IL-6 in diagnosing neonatal sepsis. Our results suggested that IL-6 is a valid and accurate index in diagnosing early neonatal sepsis, but it still needs to be combined with other laboratory tests and specific clinical manifestations.

Bioavailability/speciation of arsenic in atmospheric PM2.5 and their seasonal variation: A case study in Baoding city, China.

Arsenic (As) can be easily enriched in atmospheric particulate matters (PMs), especially in fine particulate matters (PM2.5). In this study, thirty two PM2.5 samples were collected in four seasons in Baoding, China, where the haze pollution was very serious in recent years. The total contents, species and bioavailability of arsenic in PM2.5 samples were investigated. Species of arsenic in the PM2.5 samples were discriminated as five fractions using a sequential extraction method: non-specifically sorbed fraction (F1), specifically-sorbed fraction (F2), amorphous and poorly-crystalline hydrous oxides of Fe and Al fraction (F3), well-crystallized hydrous oxides of Fe and Al fraction (F4) and residual fraction (F5). Bioavailabilities of arsenic in the PM2.5 samples were evaluated by in vitro tests using both solubility bioavailability research consortium (SBRC) and Gamble's solution extraction methods. The total volume concentrations of As in PM2.5 were significantly higher in winter than the other seasons. However, the highest mass concentration of As was found in spring. Scanning electron microscopy (SEM) characterization indicated that the physical morphology of the particles varied in different seasons. Significant differences of fraction distribution and BFs were found between different seasons. Arsenic in PM2.5 samples mainly presented in F1 with high bioavailability factor (BF), especially for the samples in summer. In vitro tests indicated that arsenic in PM2.5 could be dissolved more easily in gastric phase rather than intestinal and lung phases. There was a significant correlation between species and in vitro tests. Interestingly, a synergy effect was found between F2 and F3. Health risk assessment indicated that arsenic in PM2.5via inhalation exposure for both children and adults could cause adverse effects. Principal component analysis suggested that the arsenic in PM2.5 was from the similar sources between summer and autumn, winter and spring, respectively.

Spatial distribution of mercury in topsoil from five regions of China.

The concentrations and distributions of mercury (Hg) in topsoil from four provinces and one municipality in China were investigated. A total of 1,254 samples were collected and analyzed. The average concentrations of Hg were 0.064 mg kg(-1) for Liaoning Province, 0.100 mg kg(-1) for Jiangsu Province, 0.110 mg kg(-1) for Zhejiang Province, 0.154 mg kg(-1) for Sichuan Province, and 0.098 mg kg(-1) for Chongqing Municipality. Although differences were found among the ranges of Hg concentrations, the average values for each region were similar with other published data. The concentrations of Hg in topsoil varied largely upon the sampling locations. More than 80 % of the soil samples from Liaoning Province, Jiangsu Province, Zhejiang Province, and Chongqing Municipality, were ranked Grade I by the China Environmental Quality Standard for Soils, which can be considered as not contaminated by Hg. The concentrations of Hg in 0.3-0.4 % of soils collected from Jiangsu Province, Zhejiang Province and Chongqing Municipality exceeded the limitation for Grade III, indicating the contamination of Hg in these sites. The sources and potential risks of Hg in these sites should be brought to attention and further investigated.