Eksperimentalno ispitivanje i termodinamička analiza Bi-Ni-Pb faznog dijagrama

The article presents an experimental study of a phase diagram of a ternary Bi-Ni-Pb system using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) analysis. The investigated ternary alloys were selected from three vertical sections (x(Bi)=0.75, x(Ni)=0.1 and x(Pb)=0.9) and two isothermal sections at 100 and at 300°C. The obtained experimental results were compared with the thermodynamically extrapolated phase diagram of the Bi-Ni-Pb ternary system based on the thermodynamic parameters for the constitutive binary systems available in literature. Reasonably close agreement between the experimental data and the calculated phase diagram was obtained.U ovom radu je predstavljeno eksperimentalno ispitivanje faznog dijagrama Bi-Ni-Pb ternarnog sistema uz pomoć diferencijalne termijske analize (DTA), skenirajućeg elektronskog mikroskopa (SEM) sa energijsko disperzivno spektrometrijom (EDS) i rentgenskom difrakcijom praha (XRD). Ispitivane ternarne legure su izabrane iz tri vertikalna preseka (x(Bi)=0.75, x(Ni)=0.1 i x(Pb)=0.9), i dva izotermalna preseka na 100 i 300°C. Rezultati eksperimenta su upoređeni sa termodinamički ekstrapolisanim faznim dijagramom Bi-Ni-Pb ternarnog sistema na osnovu termodinamičkih parametara sastavnih binarnih sistema koji su dostupni u literaturi. Utvrđeno je dobro slaganje između eksperimentalnih rezultata i proračunatog faznog dijagrama

Primena metode atomske apsorpcione spektrofotometrije (AAS) za određivanje sadržaja teških metala u prehrambenim proizvodima kojima su napunjene konzerve od lakiranog belog lima

Due to possibility of contamination of food products caused by a rapid pollution of environment, as a consequence of incidents and accidents, it is necessary to exert a regular and systematic control of the content of heavy metals in tins filled with food products for the purpose of disease prevention and protection of public health. Foodstuffs, which can be of heterogeneous chemical composition contain or a considerable quantity of water, organic acids, sodium-chloride, nitrates, anthocynes, etc. are added which are the potential co rodents of metals in contact with the contents of tins. The contamination of food products in tins can also occur because of a breakthrough of a protective tin lacquer, or a poor quality of a packaging material. The consequence of the corrosion of tins is the increase of concentration of metals, especially heavy metals, the deterioration of organoleptic characteristics of foodstuff and even the perforation of tins. The atomic absorbing spectropholometer is widely used in practice for determining the content of heavy metals because of its high sensitivity (10-6 g and less), accuracy (about 1%), selectivity and the possibility of application in defining the contents of more than 20 elements. The analyzed tins were filled with pasteurized sour cherry, pasteurized apricot mash, pasteurized plum halves and sterilized peas. The aim of this research was to define the content of heavy metals in food kept in lacquered tinplate tins. Furthermore, its aim was also to determine whether the content of heavy metals in foods, upon having been tinned for several months, changes and reaches the legal level and suchlike tins can be used in human nutrition.Usled mogućnosti kontaminacije prehrambenih proizvoda zbog rapidnog zagađenja životne sredine, kao posledica incidenata i akcidenata, neophodno je vršiti redovnu i sistematsku kontrolu sadržaja teških metala u konzervama napunjenim prehrambenim proizvodima, u cilju prevencije i zaštite zdravlja stanovništva. Namirnice, koje mogu biti heterogenog hemijskog sastava sadrže, ili im se dodaje znatna količina vode, organskih kiselina, kuhinjske soli, nitrata, antocijana i dr., koji su potencijalni uzročnici korozije metala u kontaktu sa sadržajem konzervi. Do kontaminacije prehrambenih proizvoda u konzervama može doći usled proboja zaštitnog laka konzerve ili lošeg kvaliteta ambalažnog materijala. Kao posledica korozije konzervi, dolazi do povećanja koncentracije metala, naročito teških metala, do pogoršanja organoleptičkih svojstava namirnice, pa i perforacije konzervi. Za odredivanje sadržaja teških metala veliku primenu u praksi ima atomski apsorpcioni spektrofotometar, zbog visoke osetljivosti (10-6 g i manje), preciznosti (oko 1%), selektivnosti i mogućnosti primene za određivanje sadržaja preko 20 elemenata. Ispitivane konzerve punjene su pasterizovanom višnjom, pasterizovanom kašom kajsije, pasterizovanom polutkom šljive i sterilisanim graškom. Cilj ovoga rada bio je utvrđivanje sadržaja teških metala u prehrambenim proizvodima koji su se nalazili u konzervama od lakiranog belog lima. Takođe, cilj rada bio je da se utvrdi da li se sadržaj teških metala u prehrambenim proizvodima, nakon višemesečnog stajanja u konzervama, menja i dostiže zakonom dozvoljeni nivo i da li se takve konzerve mogu koristiti u ljudskoj ishrani

Determination of inorganic compounds in drinking water on the basis of household water heater scale

The concept of fractional extraction from sediment - in our analyses it is scale, is based on the assumption that uranium with a solid substance conform bonds of different strength and that these bonds can be gradually fractionated by the action of reagents of increasing dissolving power whereby the separated phases of extraction are defined according to their function or the type of bond in that substance. The advantage of this analytical procedure is that it enables simultaneous observing of different forms of uranium emergence in sediment (solid substance), which cannot be achieved by using individual extraction methods. Using the method of fractional analysis, it has been found that uranium is mostly connected with mobile fraction - manganese and iron oxides (94.20 and 87.96 wt.%) which represents the fraction that is potentially accessible to human organism.Princip frakcione ekstrakcije iz sedimenta, u slučaju naših ispitivanja kamenca, zasniva se na shvatanju da uran može da formira sa čvrstom supstancom veze različite jačine i da te veze mogu biti postupno raskinute delovanjem reagenasa rastuće jačine, pri čemu se pojedinačne faze ekstrakcije definišu na osnovu njihove funkcije ili oblika vezanosti u toj supstanci. Prednost ovog analitičkog postupka je u tome što omogućava istovremeno sagledavanje različitih oblika pojavljivanja urana u sedimentu (čvrstoj supstanci), što se ne može postići primenom pojedinačnih ekstrakcionih metoda. Metodom frakcione ekstrakcije, primenjenom u ovom radu utvrđeno je da je uran najviše vezan za potencijalno-pristupačnu i mobilnu frakciju - okside gvožđa i mangana (94,20 odn. 87,96%), što predstavlja frakciju koja je potencijalno pristupačna ljudskom organizmu

Lead and silver extraction from waste cake from hydrometallurgical zinc production

This paper presents the experimental results of the extraction of lead and silver from a lead–silver waste cake obtained in the process of hydrometallurgical zinc production. While controlling the pH value, the lead–silver cake was leached at a temperature close to boiling point in different concentrations of aqueous calcium chloride solutions. The experiments were performed applying different ratios between the mass of cake and the volume of the leaching agent under different durations of the process. It was concluded that at the optimal process parameters (pH 2.0–2.5; CaCl2 concentration, 3.6 mol dm-3; temperature, 95 °C; solid/liquid ratio, 1:5), the leaching efficiency of lead and silver could reach the approximate value of 94 %. Applying the same optimal process parameters, the method was applied to the leaching of a lead–silver cake in a magnesium chloride solution, but with significantly lower efficiencies. The results show that leaching of lead and silver in a calcium chloride solution could be a prospective method for increasing the recovery of lead and silver during hydrometallurgical zinc production