The behaviour of p,p-DDE in upland and flooded soil conditions was studied by using14C-p,p-DDE in Hangzhou, China. The dissipation speed of14C-DDE from upland soil is faster than that from flooded soil, especially in the second phase. In flooded soil, 0–8 week T1/2=3.42 (methanol extractable); 8–43 week, T1/2=10.10; in uplan soil, 0–8 week, T1/2=3.22; 8–43 week, T1/2=7.22. There is not too much difference in the distribution patten between upland and flooded soil. Most of the14C-residue is within 2 cm layer of soil column. DDE is very stable in both upland and flooded soil conditions. Experiments were carried out under natural conditions in a net house. LSC (Pachard 1900TR) was used for14C-counting. TLC technique was engaged for the analyzing of its degradation products.
This work contributed to the adsorption of radiocobalt on goethite as a function of contact time, pH, ionic strength and foreign
ions in the absence and presence of fulvic acid (FA) under ambient conditions. The results indicated that adsorption of Co(II)
was dependent on ionic strength and foreign ions at low pH values (pH < 7.8), and independent of ionic strength and foreign
ions at high pH values (pH > 7.8). Outer-sphere surface complexation and/or ion exchange were the main mechanisms of Co(II)
adsorption on goethite at low pH values, whereas inner-sphere surface complexation was the main adsorption mechanism at high
pH values. The presence of FA enhanced Co(II) adsorption at low pH values, but reduced Co(II) adsorption at high pH values.
The thermodynamic data (ΔH0, ΔS0, ΔG0) were calculated from the temperature dependent adsorption isotherms, and the results suggested that adsorption process of
Co(II) on goethite was spontaneous and endothermic. The results are crucial to understand the physicochemical behavior of
Co(II) in the nature environment.
Authors:Shi Xu, Sheng Li, Yun Wei, Li Zhang, and Fei Xu
Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.
Authors:Linglin Xu, Peiming Wang, and Guofang Zhang
The influence of calcium sulfate with different reactivities (anhydrite, α-hemihydrate, and gypsum) on the Portland cement–calcium aluminate cement (PC/CAC) mixtures was presented in the paper. The hydration process and main hydration products (ettringite) of the binders with different content of calcium sulfate was investigated by isothermal conduction calorimetry, setting times, compressive strength, X-ray diffraction (XRD) analysis, and environmental scanning electronic microscope (ESEM) analysis. It is found that the pure PC/CAC mixture without any calcium sulfate addition exhibits very slow hydration kinetics during the first 2 days. By adding calcium sulfate, the setting of the PC/CAC mixture is delayed, but the hydration can be accelerated. The results also show that the reactivity and the amount of the calcium sulfate determine the balance between the hydration products of ettringite and monosulphoaluminate, and also the early hydration kinetics not only in the formation content but in the location of ettringite. In general, when a high content of reactive α-hemihydrate is added, much secondary gypsum forms in voids between cement granules which exert adverse effects on the properties of PC/CAC mixtures. Additionally, ettringite can be formed stably and good binders having good physical properties can be obtained when low reactive anhydrite is added.
This paper provides an overview of the progression of technology structure based on patent co-citation networks. Methods of patent bibliometrics, social network analysis and information visualization are employed to analyze patents of Fortune500 companies indexed in Derwent Innovations Index, the largest patent database in the world. Based on the co-citation networks, several main technology groups are identified, including Chemicals, Petroleum Refining, Motor Vehicles, Pharmaceuticals, Electronics, etc. Relationships among the leading companies and technology groups are also revealed.
Authors:Fan Lan, Xiang Wang, Xianglan Xu, Rongbin Zhang, and Ning Zhang
SnO2 catalysts were prepared with the precipitation method by varying the pH and SnCl4 concentration. For comparison, another two SnO2 samples were also synthesized with sol–gel and combustion methods. All of the catalysts were characterized by N2-BET, XRD and H2-TPR. It was found that the CO oxidation activity of the precipitation samples increases with an increase in pH, while the CH4 oxidation activity seems unchanged. The change of the SnCl4 concentration has little influence on the activity for both CO and CH4 oxidation. The sol–gel sample has relatively higher CO but similar CH4 oxidation activity, due to its higher surface area and finer particle sizes. On the contrary, the combustion sample displays the lowest activity for both reactions, due to its extra low surface area and inert oxygen species.
Authors:G. Xu, L. Zhang, L. Liu, G. Liu, and D. Jia
Thermal behaviors of two mixed-ligand complexes, [Ni(PMPP-SAL)(Py)3] and [Cu(PMPP-SAL)Py]·MeOH, (PMPP-SAL=1-phenyl-3-methyl-4-(salicylidene hydrazide)-propenylidene-pyrazolone-5, Py=pyridine),
were studied by TG-DTG-DTA in dynamic air atmosphere. The complexes show the loss of pyridine molecule is followed by the
decomposition of the PMPP-SAL anion and give respective metal oxides as residues. Meanwhile, the Ozawa-Flynn-Wall model-free
analyses and multivariate non-linear regressions were applied to perform single and overall steps optimization. Kinetic parameters
were given and the most probable mechanism functions were suggested in this study.
Passive air samplers (polyurethane foam disks) were deployed at 25 urban sites and 66 rural sites over the period of July
to October 2005, partly between October 2005 and January 2006 for about 120 days across China, and analyzed for extractable
organo-chlorine /-bromine /-iodine (EOCl/EOBr/EOI) and polychlorinated biphenyls (PCBs) using hybrid neutron activation analysis
(NAA) combined with gas chromatographymass spectrometry (GC-MS). The average concentration of EOCl, EOBr, EOI and ΣPCBs among
all the sites were 173.7, 3.5, 1.0 and 0.74 ng/d, respectively. Higher values of EOCl/Br/I and PCBs were detected in the areas
of high usage and high emission, which were linked to relatively high-income areas in China, while lower in the west ill-developed
region of China, which indicated that these pollutants mainly came from industrial pollution. Higher EOCl contents in traffic
areas stated that the exhaust emission from vehicle was another main source of organochlorines in the air. The relative proportions
of the known organochlorines (84 PCB congeners) to total EOCl were 0.02–3.0%, which implied that most of EOCl measured in
air were unknown.
To effectively extract organohalogens from human hair, two factors, the extracting time and hair length on the extraction
efficiency of organohalogens were studied by neutron activation analysis (NAA) and gas chromatograph-electron capture detector
(GC-ECD), respectively. Furthermore, the concentrations of extractable organohalogens (EOX) and extractable persistent organohalogens
(EPOX) in hair samples from angioma and control babies were also measured by the established method. The results indicated
that the optimal Soxhlet-extraction time for EOX and EPOX in hair was from 8 to 11 hours, and the extraction efficiencies
for organochlorine pesticides in hair were in the order of powder >2 mm>5 mm. Also, the mean levels of EOC1 and EPOC1 in hair
of the angioma babies were significantly higher than those in the control babies (PEOC1<0.01; PEPOC1<0.05), which implied the possible relationship between the environmental pollution and angioma.
Authors:Qichu Xu, Jianfeng Wu, Lixing Zhang, and Yusheng Yang
Extraction of Am(III) and Ln(III) from NaClO4 medium with di(2-ethylhexyl)dithiophosphoric acid (DEHDTP), di(2-ethylhexyl)monothiophosphoric acid (DEHMTP), di(2-ethylhexyl)monothiophosphinic
acid (DEHMTPI), dihexyldithiophosphinic acid (DHXDTPI), diheptyldithiophosphinic acid (DHPDTPI), dioctyldithiophosphinic acids
(DODTPI), dinonyldithiophosphinic acid (DNDTPI), di(1-methylheptyl)dithiophosphinic acid (DMHDTPI) and di(2-ethylhexyl)dithiophosphinic
acid (DEHDTPI) in xylene has been investigated. The order of the extraction selectivity for Am(III) is DEHDTPI > DEHDTP >
DEHMTPI > DEHMTP, DHPDTPI > DODTPI > DHXDTPI > DNDTPI, DMHDTPI > DEHDTPI > DODTPI, for extractants with 2-ethylhexyl alkyl,
straight chain alkyl, branch chain alkyl, respectively. Using 0.1 mol/l NaClO4 solution as aqueous phase, the slope values of the logD-pH and logD-logC curves are not integers, and the slope values for Am(III) are slightly higher than those for Eu(III), for all extractants.
The relationship between the slope value and extraction conditions can be described as: logS = alg(CHA/CMS/4)+b. In the presence of macro Eu(ClO4)3, the formula, logSFAm/Ln = B-2log(CHL-DLn/(DLn + 1)CEu), can well describe the relationship between separation factor and the extraction condition. A high separation factor (SFAm/Eu = 2500) is obtained by solvent extraction with 0.5 mol/1 DEHDTPI in toluene from 1 mol/l NaNO3 solution.