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  • Author or Editor: N. Benfaid x
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Abstract  

Cement is widely used as a construction material in Libya. Production plants introduce certain contaminants to the environment. The dust from such plants is carried away to neighbouring areas. This dust contains a substantial amount of contaminants depending on the origin of clays used in the production. In this study, a survey of elemental concentration of clay and cement was carried out to assess the environmental impact of such plants, especially those that are situated near residential and agricultural areas. Cement and clay samples, imported and locally produced, were analyzed. Instrumental neutron activation analysis was utilized to determine the elemental concentration of As, Ca, Ce, Co, Cr, Eu, Fe, Hf, La, Na, Rb, Sb, Sc, Sm, Ta, Th, U, Yb and Zn. Elevated concentrations of U and Th were found in a number of cement samples. The two nuclides are part of an elaborate decay scheme producing a range of radioactive elements, which emit alpha-, beta- and gamma-radiation. With 40K, they could give elevated levels of background radiation in buildings resulting in higher exposure doses. This could pose a health hazard and a detrimental effect on the well being of residents, especially in poor ventillated buildings. Also, cement is the main component for constructing underground reservoirs for collecting rainwater for drinking in private residences, so some harmful elements could leach into water. This is the first comprehensive survey of commercial cement brands and clays used in Libya. These results are intended to build a database for trace element concentrations using INAA.

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Thermal behaviour of acidic salts of mixed tetravalent metals

II. Thermal decomposition of various intercalated mixed zirconium-titanium phosphates

Journal of Thermal Analysis and Calorimetry
Authors:
L. Szirtes
,
J. Kern
,
L. Pavlovszki
,
S. Shakshooki
,
Y. Elmismary
,
N. Benfaid
, and
S. Haraga
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Abstract  

Solid ZrOCl2·8H2O was added in a slow stream to a solution of phosphoric acid or to a solution of TiCl4 in phosphoric acid to obtain granules of amorphous Zr(HPO4)2·nH2O or ZrxTi(1–x) (HPO4)2·nH2O(where x=0.95–0.80). Half of each product had been soaked in ethanol to produce alcohol solvated materials. It was found that the particle size of the resulting materials is very similar to that of ZrOCl2·8H2O, in such a way that it may be controlled indirectly. These materials are suitable for ion-exchange column operations. The relatively high gamma radiation doses of60Co source did not alter its exchange properties. pH-titrations were performed by an automatic titrimeter and the exchange capacities of alkali metal ions were determined by isotopic tracer technique. Effect of drying temperature on the ion exchange properties of Na+, K+ and Cs+ on the granular materials have been studied. Other characterizations were made by usual chemical analysis and thermography.

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Thermal behaviour of acidic salts of mixed tetravalent metals

III. Influence of gamma-radiation on the thermal decomposition of mixed zirconium-titanium phosphates

Journal of Thermal Analysis and Calorimetry
Authors:
L. Szirtes
,
J. Kern
,
L. Pavlovszki
,
S. Shakshooki
,
A. Dehair
,
Y. Mismary
,
N. Benfaid
,
S. Haraga
, and
A. Benhamid
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