An emprical study has been conducted to determine the ability of common granitic fracture-filling minerals to remove aqueous iodine species from solution. The two iodine species studied were iodide and iodate. The effect on measured sorption of the initial iodide or iodate concentration in solution, the total dissolved solids in solution and the solution volume to solid weight ratio were determined using a statistically designed experimental technique. It was concluded that iodide was not significantly sorbed by chemical interaction with the fracture-filling minerals used. Iodate sorption was observed under a variety of conditions with a number of the minerals. The significant coefficients required to solve the polynomial equation describing the observed sorption were determined.
Certain five-membered dioxaheterocyclic compounds (hetero atoms may be P, Si, S, etc.) contain a strained carbon–carbon bond
which may undergo homolytic thermolysis at modest temperatures to generate a diradical capable of initiating vinyl polymerization.
If substituents contain flame-retarding moieties this represents a convenient method for imparting flame retrdancy to a polymeric
material. Of particular interest has been 2,4,4,5,5-pentaphenyl-1,3,2-dioxaphospholane. The thermal degradation of this compound
has been studied using 13C NMR spectroscopy. This may conveniently be done by monitoring the intensity of the signal for the benzylic carbon atom as
a function of time and temperature. A simple transformation is the conversion of the cyclic compound to the linear polymer.
General purpose poly(styrene) is a large
volume commodity polymer widely used in a range of applications. For many
of these the presence of an additive to impart some flammability resistance
is required. Most commonly, brominated aromatics are used for this purpose.
As the polymer undergoes combustion these compounds decompose to generate
bromine atoms and/or hydrogen bromide which escape to the gas phase and trap
flame propagating radicals. While these species are effective in inhibiting
flame propagation they present the opportunity for loss of halogen to the
atmosphere. For this reason, the use of these compounds is being limited in
some parts of the world. Phosphorus compounds, on the other had, impart a
flame retarding influence by promoting char formation at the surface of the
burning polymer. This prevents heat feedback to the polymer and consequent
pyrolysis to generate fuel fragments. The combination of both bromine and
phosphorus present in a single compound might generate a superior flame-retarding
additive in that both modes of retardancy might be promoted simultaneously.
Should this be the case smaller amounts of additive might be necessary to
achieve a satisfactory level of flame retardancy. A series of such additives,
brominated aryl phosphates, has been synthesized and fully characterized spectroscopically.
Blends of these additives, at various levels, with poly(styrene) have been
examined by DSC, TG and in the UL-94 flame test. The flammability of the polymer
is dramatically diminished by the presence of the additive.
The purpose of this paper is to study necessary and sufficient conditions for the Ishikawa iterative sequence with mixed errors
of asymptotically quasi-nonexpansive type mappings in Banach spaces to converge to a fixed point in Banach spaces. The results
presented in this paper complememt, improve and prefect the corresponding results of – and –.
The scavenging of UO22+ using 4-sulfonic calixarene in the presence of a strong adsorbent was studied as a function of pH. The adsorbent selected
was goethite because of its strong affinity for UO22+ and its abundance in natural soils. In order to understand the underlying chemistry of the scavenging process, the adsorption
of UO22+ and 4-sulfonic calixarene onto goethite, respectively, and the extraction of adsorbed UO22+ from goethite surface were modeled using the triple-layer model. The model well explained the pH dependence of the adsorption
and extraction processes. This work showed that maximum extraction was obtained around pH 10.5 in the presence of 12g/l goethite
in the case of a 1:3TU(VI):Tcalixareneratio.
Fully substituted 1,3-dioxa-2-siloles contain a strained carbon–carbon bond that will undergo thermolysis at modest temperatures to generate a diradical capable of initiating vinyl polymerization. If the substituents contain flame-retarding moieties, e.g., halogen or phophorus-containing groups, the use of such compounds as initiators serves to incorporate a flame-retarding unit into the polymer mainchain. Both 2,2-dialkyl- and 2,2-diaryl-4,4,5,5-tetra(3,5-dibromophenyl)-1,3-dioxa-2-siloles may be prepared from the appropriate tetra(bromoaryl)-1,2-ethanediol and are obtained as white solids. Thermal decomosition (thermogravimetry) of these materials occurs in two stages. Initial decomposition is observed at about 250 °C and corresponds to the loss of nearly half of the initial sample mass.
Nondestructive neutron activation technique was used to analyze 17 elements (Al, As, Au, Ba, Br, Cl, Cu, Hg, I, K, Mg, Mn,
Na, Sb, Sr, V and Zn) in 75 human hair samples in 5 different locations, respectively, from 15 glassware workers. The analytical
results were treated further statistically to find the elemental distribution among different human hairs and to identify
the individual's hair. The identifying probability of one's hair by the comparison of elemental concentrations is found to
be 104–106 times higher from the same person's than from any other person's. The standard deviation of the elemental concentrations
of samples taken from 5 different locations of one person is about 5 times smaller than the standard deviation for individual's
hair. These data support the possibility of using NAA of hair for human hair identification.
A nondestructive instrumental neutron activation technique was used to analyze human hair samples collected from people living in metropolitan and rural areas in Korea. Samples were also collected from factory workers and cancer patients. Hair from metropolitan area residents contain higher concentrations of Ca, Mg, Zn, Cu, Na, Br, Mn, I and S than rural area residents. Concentrations of I and S from cancer patients, Mg, Zn, Al, Na, Mn and As from glassware workers were relatively higher. The results show that the trace element concentrations of the hair are possibly related to the trace element concentrations in the body.
Trace elements in airborne particulate matter collected monthly at suburban and rural areas in Korea were analyzed by instrumental neutron activation analysis (INAA). Neutron irradiation of the samples was done at the irradiation hole (neutron flux 1·1013 n·cm–2·s–1) of the TRIGA Mark-III Research Reactor in the Korea Atomic Energy Research Institute. For the verification of the analytical technique, two reference materials, NIST SRM-1648 and NIES CRM-8, were chosen for analysis. The accuracy and precision of the determinations of the 40 elements were compared with the reference values. We used this method (1) to analyze 30 trace elements in airborne particulate matter collected monthly with the high volume air sampler (PM-10) at two different locations and (2) to confirm the possibility of using this method as a routine monitoring tool to find out environmental pollution sources.
Authors:K. Lee, Y. Yoon, S. Cho, K. Ko, and Y. Kim
Naturally occurring radionuclides (NORN) such as 40K, 226Ra and 232Th from 44 surface sediment samples collected from four desert regions of Chinese were determined to investigate the regional
characteristics of the source areas of Asian dust. The radionuclides for 41 surface sediment samples collected from seven
sites of the Keum River area in Korea were also determined to compare the regional characteristics with the Chinese desert
area. The specific activities (SA) and the specific activity ratios (SAR) of the radionuclides were investigated for distinguishing
the source region of Asian dust. The SA of 226Ra and 232Th as well as the SAR of 226Ra/40K and 232Th/40K were found to be useful to characterize source area and tracing Asian dust.