نتایج جستجو برای: free silica
تعداد نتایج: 549038 فیلتر نتایج به سال:
this research was conducted from july 1993 to june 1994 on the total population (711 workers) of a glass factory. the purpose of this study was to determine the quantitative free silica (quartz) in respiratory zone of workers in glass industry. field samples including 50 samples total dust and 37 samples respirable dust and standard simplex were collected on membrane filters using skc dust samp...
Background and Objectives: Silica is an inorganic material that found in the nature in various forms. The hazards of crystal of silica or α-quartz (free silica) is greater than other forms. Exposure to dust that contains free silica result to pulmonary injury and result to silicosis and death finally. The present research was conducted in order to evaluate the level of workers exposure to free ...
an efficient green route for the preparation of naphthoxazinones, applying a three-component one-pot condensation reaction of 2-naphthol, aromatic aldehyde and urea in the presence of nano silica supported ferric chloride under solvent-free conditions has been developed. the present procedure offers several advantages such as short reaction time, simple workup, recovery and reusability of the c...
nano sio2/hyperbranched polyglycerol (hpg)/so3h catalyst was readily prepared for first time from inexpensive starting materials in aqueous media which catalyzed the synthesis of benzoic acid. ftir spectra, x-ray diffraction (xrd) and transmission electron micrographs (tem) was employed to characterize the properties of the synthesized nano sio2/hpg/so3h. high catalytic activity and ease of rec...
Abstract Background and purpose: Workers' exposure to respirable silica particles especially free crystalline silica in workplace could result in some dangerous diseases such as silicosis or lung fibrosis. This study was carried out to evaluate the workers' exposure to free crystalline silica particles in some industries using the infrared spectrophotometery method. Materials and methods: I...
an efficient and environmentally benign method for the synthesis of aryl iodides have been developed by diazotization of aromatic amines with nano2 and nanosilica periodic acid (nano-spia) as a green catalyst via grinding followed by a sandmeyer iodination by ki under solvent-free conditions at room temperature. the ensuing aryl diazonium salts supported on nano-spia were sufficiently stable ...
nano silica-h2so4 is an efficient and mild catalysis system for the regeneration of aldehyde from aldoximes. ketoximes are converted to amides by beckmann rearrangement in the presence of nano silica-h2so4. the reactions are carried out in solvent-free conditions under microwave irradiation (600 w) within 50-120 sec in good yields.
Introduction & Objective: Determination of free silica to calculate threshold limit value is necessary. The purpose of this research was study of free silica in particulate emission in ambient air of stone crushing workshops in Azandarian area. Materials & Methods: 40 samples of respirable dust from workplace air were obtained in breathing zone of workers in different job stations. Samples...
silica sulfuric acid is employed as solid acid catalyst for the clean and less hazardousprotection of carbonyl compounds as 2,4-dinitrophenylhydrazone under solvent-free conditions.
a mild and green method has been developed for the preparation of coumarins derivatives through the one-pot reactions. in our study,various phenols and ethyl acetoacetate compound in which we used silica-supported boron sulfonic acid [sio2/b(so4h)3] as a new, highly efficient and tri-functional inorganic brønsted acid catalyst were processed under solvent-free condition and thermal. the catalys...
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