Enhanced catalytic sulfamethoxazole degradation via peroxymonosulfate activation over amorphous CoSx@SiO2 nanocages derived from ZIF-67.

In this work, the amorphous CoSx@SiO2 nanocages were hydrothermally synthesized by sulfurizing ZIF-67@SiO2 in the presence of thioacetamide (TAA). The catalytic performances of CoSx@SiO2 nanocages as heterogeneous catalysts to activate peroxymonosulfate (PMS) for the sulfamethoxazole (SMX) degradation were systematically investigated. 100% SMX was degraded within 6 min in CoSx@SiO2/PMS system, indicating that the amorphous CoSx@SiO2 nanocages exhibited outstanding sulfate radical-advanced oxidation process (SR-AOP) activity toward SMX degradation due to the regeneration of Co2+ by surficial sulfur species like S2-/S22-. The effects of PMS dosages, initial pH, SMX concentrations and co-existing ions on SMX degradation efficiency were explored in detail. The SMX removal efficiency was obviously improved in the simulated wastewater containing chloride ions (Cl-) and low-concentration bicarbonate ions (HCO3-). The residual PMS and the generated sulfate radical (SO4·-) were determined quantitatively in CoSx@SiO2/PMS system. A possible mechanism in CoSx@SiO2/PMS system was proposed based on the results of quenching experiments, X-ray photoelectron spectroscopy (XPS) analysis, electrochemical tests, and electron spin resonance (ESR). The CoSx@SiO2 exhibited good stability and reusability, in which 100% SMX removal was achieved even after five consecutive cycles. This work provided a strategy for regulating the stability of cobalt-based catalyst for efficient pollutant degradation by PMS activation.

Bioaccessibility and risk assessment of cadmium from uncooked rice using an in vitro digestion model.

Cadmium (Cd)-contaminated rice is one of the most important sources of cadmium exposure in the general population from some Asian countries. This study was conducted to assess cadmium exposure from uncooked rice in rural mining areas based on the bioaccessible fraction of cadmium using an in vitro digestion model. The biotoxic effects of cadmium in uncooked rice from mining areas were much higher than those in the control area, based not only on their higher total concentration (52.49 vs. 7.93 µg kg(-1)), but also on their higher bioaccessibility (16.94% vs. 2.38%). In the mining areas, the bioaccessible fraction of cadmium in uncooked rice has a significant positive correlation with the total concentration of cadmium in rice and there was quarterly unsafe rice to the public in the mining areas. The results indicated that the in vitro digestion model could be a useful and economical tool for providing the solubilization or bioaccessibility of uncooked rice in the mining area. The results could be helpful in conducting future experiments of cooked rice in the vitro model.

[Remediation Pb, Cd contaminated soil in lead-zinc mining areas by hydroxyapatite and potassium chloride composites].

The composite agents containing potassium chloride (KCl) and Hydroxyapatite (HA) were used to remediate the lead and cadmium contaminated soil in Fenghuang lead-zinc mining-smelting areas, Hunan province. The objective of this study was to identify and evaluate the influence of Cl- to the fixing efficiency of Pb and Cd by HA. Two types of contaminated soil (HF-1, HF-2) were chosen and forty treatments were set by five different Hydroxyapatite (HA) dosages and four different Cl- dosages. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the results. It showed that HA could efficiently fix the Pb and Cd from TCLP form. The maximum Pb-fixing efficiency and Cd-fixing efficiency of two types of soil were 83.3%, 97.27% and 35.96%, 57.82% when the HA: Pb: KCl molar ratio was 8: 1: 2. Compared to the fixing efficiency without KCl, KCl at the KCl: Pb molar ratio of 2 improved Pb-fixing efficiency and Cd-fixing efficiency by 6.26%, 0.33% and 7.74%, 0.83% respectively when the HA: Pb molar ratio was 8. Generally, Cl- can improve the Pb/Cd-fixing efficiency in heavy metal contaminated soil by Hydroxyapatite.

[Determination of five trace elements (Pb, Cd, Se, As and Hg) in human whole blood by temperature-controllable wet digestion and ICP-MS technique].

A method for the determination of five trace elements, including Pb, Cd, Se, As and Hg concentrations in human whole blood by HNO3-H2O2 digestion under temperature-controllable condition and ICP-MS was described. Under the optimum experimental conditions and instrumental operation parameters, the limit of detection for the five elements were 2-40 ng x L(-1). The system had a good stability with RSDs of the determination of value repeated 3 times less than 3%. The accuracy of the method was evaluated by the results of determination of the Chinese national standard references GBW(E)09034-09036 and GBW09101b, and the analytical results well agreed with the certified values. Using this method, the concentration of the five elements in whole blood of 34 habitants from mercury mining area in western Human province was studied. The result showed that the blood Se and blood As level was at security scope, however, blood Pb, Cd and Hg level was too high and beyond the safety thresholds which should be concerned about. The analytical method mentioned above can be used for determination of trace elements in human blood to achieve a convenient and rapid operation and accurate result.

[Temporal and spatial variation rule of methylmercury in water in the Second Songhua River].

The concentrations of methylmercury (MeHg) in water were investigated in both level period and flood period in the Second Songhua River. The results show that the MeHg concentrations in water of Hongshi, Shihaoxian and Ganshuigang sites are relatively higher than other sampling sites. The MeHg concentrations in the level period are higher than the flood season in most sampling sites beside Laozhou and Sifangtai sites. By comparing the MeHg concentrations in different years, the results reveal that the MeHg concentrations in 1981 decreased with the distances increasing from the sites to the pollution source. The MeHg concentrations in most sites greatly fell in 1983, when the pollution source had been ceased for one year. The concentrations approached the natural background level in most sites, however, they were over 0.35 ng x L(-1) from Zhaoyuan site to Sifangtai site. The MeHg concentrations in corresponding sites in 2006 were higher than that in 1983, but were lower than that in 1981. Moreover, the pollution level in water of the Second Songhua River was also discussed.

[Total and methyl mercury contents in arthropods].

We researched mercury contents in plants and arthropods collected from the river banks in mercury polluted areas. The results show that total mercury (T-Hg) and methyl mercury (Me-Hg) in Locusta migratoria manilensis and Acrida chinensis are 0.032 - 0.402 mg x kg(-1), 0.023 - 0.362 mg x kg(-1) and 0.003 - 0.031 mg x kg(-1), 0.004 - 0.015 mg x kg(-1) while the proportion of Me-Hg to T-Hg are 3.5% - 49.7% and 2.0% - 44.4%. T-Hg in arthropods is higher than that a magnitude in non-polluted areas. As primary consumers, mercury contents in Locusta migratoria manilensis and Acrida chinensis are lower than plants they eat. That is not consistent with the non-polluted areas. Paratenodera sinensis is the second consumer and there is an obvious mercury accumulation in it. For Locusta migratoria manilensis, T-Hg decreased with the body length while for Acrida chinensis that increased following a decreasing. But Me-Hg in both increased with body length. Mercury contents in tissues of arthropods are significantly different. The order is abdomen > thorax > head. Mercury and methyl mercury contents in arthropods would lead wild birds, fowls and amphibians in the ecologic risk condition.