From the aspect of their chemical and mineralogical composition, bauxites are very complex multicomponent raw materials. The paper presents the characterization of bauxite from several different deposits: Brazil, Milići, Čitluk and Kosovo. Chemical characteristics were determined by a combination of different analytical methods: gravimetry, potentiometric titration, atomic absorption spectroscopy (AAS) and UV-VIS spectrophotometry. Mineralogical composition was determined using X-ray diffraction and thermal analysis methods. Chemical and structural characterization is complemented by the results of scanning electron microscopy with EDX analysis. The information obtained was used for the assessment of the quality of investigated bauxites from the aspect of their application in the production of alumina.
The composition of composites has a huge impact on the stability of tris-1,10--phenanthroline iron (II) complex during the determination of total iron. The subject of this work is the determination of the stability of tris-1,10-phenanthroline iron (II) complex in different composites. The composites with different concentration in which total iron was determined were alumina and zeolite. The stability of this complex was monitored in the time period of 0-60 min. The aim of this work is to determine the concentration of different composite samples and the time interval in which the stability of the complex is the highest. The spectrophotometric method was used for the determination. The tris-1,10-phenanthroline iron (II) complex with alumina is more stable at higher concentration of the samples. With zeolite, however, this complex is stable in a short time interval, regardless the concentration of the sample. This conclusion indicates the increase of absorption, which is a consequence of impede complex formation and creating a new complex. For this reason, this method has only a limited application.
U radu je praćena adsorpcija propan kiseline iz vodenog rastvora na visokosilikatim zeolitnim uzorcima, proizvedenim savremenim nanotehnologijama u američkoj kompaniji Zeolyst International (oznaka: CBV 28014). Kao adsorbensi korišteni su NH 4 ZSM-5 zeolit i njegova modifikovana forma-HZSM-5 (molski odnos SiO 2 /Al 2 O 3 iznosi 280). Adsorpcija je praćena u temperaturnom intervalu od 283 K do 303 K. Rezultati su pokazali da je sa porastom temperature adsorpcije količina adsorbovane propan kiseline rasla i na izvornoj i na modifikovanoj formi ZSM-5 zeolita, što ukazuje da se pored fizičke adsorpcije dešava i hemisorpcija, pri čemu su molekule kiseline vezane za aktivne centre i čvršćim hemijskim vezama. Modifikacijom osobina izvornog zeolita dobio se bolji adsorbens (HZSM-5 zeolit) za propan kiselinu, što je i očekivano obzirom na izražen hidrofobni karakter ove modifikovane forme.
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