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Surfactant modification and adsorption properties of clinoptilolite for the removal of pertechnetate from aqueous solutions
No full textNatural clinoptilolite modified with a cationic surfactant stearyldimethylbenzylammonium chloride (SDBAC) was used as an adsorbent for the removal of pertechnetate from aqueous solutions. Adsorption studies were performed in a batch system. The effects of various experimental parameters (amount of surfactant loading, contact time, solution pH, competing anions) on the removal efficiency of TcO4 (-) were investigated. SDBAC-clinoptilolite with organo-bilayer was successfully used to remove TcO4 (-) from aqueous solutions in the pH range of 5.0-8.0. ReO4 (-) as an analogue of TcO4 (-) was used to model the isotherms. Adsorption capacity of the SDBAC-clinoptilolite and the mechanism of ReO4 (-) (TcO4 (-)) sorption were also determined
Carbonate filler resources of the Bjelopavlici area, Montenegro
No full textCarbonate filler is an important mineral commodity, with rather diverse industrial applications. The Bjelopavlici area in Montenegro is rich in chemically pure limestone, which was preliminary explored in the field, and further its mineralogical, petrographic, geochemical and technological properties were studied. The obtained results have proven the high quality of limestone from the studied deposits, as it can be used for paints and varnishes, rubber and plastics, metallurgy, foundry, sugar, fertilizers and animal feed industry. Several deposits have very pure limestone, that can be also used for paper, glass, pharmaceutical industry and soil neutralisation. The potential resources of high quality limestone are around 23 million tons
Synthesis of Highly Porous Al2O3-YAG Composite Ceramics
No full textAl2O3-YAG composite was obtained by sintering of porous Al2O3 preforms infiltrated with water solution of aluminium nitrate nonahydrate, Al(NO3)(3)center dot 9H(2)O and yttrium nitrate hexahydrate, Y(NO3)(3)center dot 6H(2)O. Al2O3 preforms with porosity varying from 26 to 50% were obtained after sintering at temperature ranging from 1100 to 1500 degrees C. Sintering of the infiltrated Al2O3 preforms led to formation of YAG particles due to reaction between Y2O3 and Al2O3 at high temperature. It was found that variation of porosity of alumina preforms and sintering temperature is an effective way to fabricate Al2O3-YAG composite with an unusual combination of properties. Open porosity was in the range 15-35%, specific surface was 0.6-6.1 m(2)/g, pore size was 150-900 nm whereas compressive strength was from 50 to 250 MPa. The effect of sintering temperature on YAG formation and phase composition were investigated using X-ray diffractometry whereas microstructure of the composite was analysed by scanning electron microscopy
Hydrothermal conversion of grape pomace: Detailed characterization of obtained hydrochar and liquid phase
No full textIn this study, carbonization products of grape pomace (hydrochar and process water) have been thoroughly characterized in order to assess its fuel properties, physico-chemical composition and to optimize its production. The obtained detailed insight into transformations of the biomass during hydrothermal conversion between 180-220 degrees C revealed that the hydrochar obtained at 220 degrees C exhibits a considerable energetic potential, increased porosity and re-adsorption abbility. Hydrothermally induced structural changes in the obtained hydrochars were unveiled by thermal and morphology analysis, FTIR and NIR spectroscopy. Temperature increment caused a decrease in antioxidative capacity, anthocyanin and organic acid content in process water and simultaneous increase in total phenolic and individual organic components content. The overall effect of the reaction temperature on products characteristics was assessed by multivariate data analysis. Obtained results substantiated the suitability of hydrothermal conversion of grape pomace into highly valuable fuels and versatile products
Utilization of waste materials from flotation plant „Feldspar“ Bujanovac
No full textThis paper gives a review of results determining conditions of thickening and filtration of waste material from the flotation plant “Feldspar” – Bujanovac. This flotation plant last few years did not fuctiona as should be, and have many problems. Investigation of waste materials, should to enable recycling and re-use of flotation tailings. Tests of possibilities of thickening and filtration of the non-magnetic fraction of waste material sample of the class -0,063 mm after magnetic separation in laboratory conditions have been carried out within this research. Based on dewatering testing, time of thickening and calculated results have been determined
Biosorption of Cu2+ from aqueous solution by hydrochar of grape pomace
No full textHydrothermal carbonization is a promising route for conversion of lignocellulosic biomass into biofuels, adsorbents and specific chemicals. Herein, the evaluation of grape pomace as a precursor to obtain hydrochar, an adsorbent of copper from wastewaters, using hydrothermal conversion was performed. By examining the effect of sorbent dose and contact time, the ability of grape pomace hydrochar to effectively remove copper from aqueous solutions was confirmed. The obtained adsorption isotherms were best described by the Langmuir model. FTIR analysis of samples before and after adsorption supports the proposed mechanism of metal binding onto hydrochar surface
Uticaj elektromagnetnog polja tokom livenja na karakteristike odlivaka aluminijumskih legura
No full textElektromagnetni postupak livenja zasniva se na teoriji metalurških procesa i magnetohidrodinamici. Prilikom livenja u prisustvu elektromagnetnog polja naizmenična struja generiše vremenski promenljivo mognetno polje u istopljenoj masi što povećava indukovanu struju u rastopu. Rastop metala je pod uticajem elektromagnetne sile koja je prouzrokovana interakcijom indukovane struje i magnetnog polja. Elektromagnetna sila izaziva veći protok fluida, prinudnu konvekciju, ravnomernije temperaturno polje i slabiji uticaj gravitacije. Na ovaj način se menjaju uslovi očvršćavanja. Dobijeni odlivci su kvalitetniji, struktura je finija i uniformnija po preseku. Zbog smanjenog kontaktnog pritiska, (što je takođe posledica delovanja elektromagnetnog polja) između kalupa i metala, kvalitet površine je poboljšan tako da nije potrebna veća dodatna mašinska obrada. U svetu postoje određena istraživanja u oblasti elektromagnetnog postupka livenja, ali je malo pažnje posvećeno karakterizaciji mikrostrukture i mehaničkih svojstava tako dobijenih odlivaka. Ovaj rad treba da doprinese boljem poznavanju uticaja elektromagnetnog polja na dobijenu mikrostrukturu (morfologiju, veličinu zrna, raspodelu i udeo dobijenih faza) i ostale karakteristike dobijenih odlivaka. Izabrana legura EN AW 7075 ima široku primenu u industriji, termički je obradiva i namenjena je za plastičnu preradu odnosno kovanje. Proizvodnja ove legure je dugotrajna i skupa, a prate je nedostaci tipa poroznosti, toplih pukotina i neujednačenosti u veličini zrna. Ove metalurške greške utiču na pogoršanje mehaničkih svojstava i kvaliteta dobijenih odlivaka. U cilju smanjenja ovih grešaka još u livenom stanju neophodno je primeniti odgovarajući postupak livenja sa optimalnim radnim parametrima. Da bi se ispitao uticaj elektromagnetnog polja prilikom livenja upoređeni su uzorci odliveni bez dejstva polja i pod dejstvom polja različite frekvencije 10, 15, 20 i 30 Hz. Rezultati ispitivanja mikrostrukture i mehaničkih svojstava pokazuju da je primenom elektromagnetnog polja moguće dobiti finiju i homogeniju mikrostrukturu, a samim tim i bolja mehanička svojstva. Dobijeni rezultati SEM/EDX, DTA analize kao i rezultati merenja elektroprovodljivosti i određivanja hemijske segregacije su prikazani i upoređeni. Primena matematičkih modela u obradi rezultata i numerička simulacija procesa toplog kovanja su urađeni prateći svetske trendove, a njihova praktična primena ima za cilj uštedu energije, smanjenje škarta i potrošnju sirovina Dobijeni rezultati se mogu koristiti za proširenje baza podataka primenjenih modela. Ova doktorska disertacija je rezultat istraživanja u okviru projekta „Razvoj tehnoloških postupaka livenja pod uticajem elektromagnetnog polja i tehnologija plastične prerade u toplom stanju eetvorokomponentnih legura Al-Zn za specijalne namene“, TR 34002, čiji je rukovodilac prof. dr Zvonko Gulišija, naučni savetnik, a koji finansira Ministarstvo prosvete, nauke i tehnološkog razvoja Republike Srbije u okviru programa tehnološkog razvoja u periodu od 01. 01.2011. – 30. 06. 2016. godine.Electromagnetic casting (EMC) is the technology developed as by combining the magnetic hydrodynamics and casting technique. Electromagnetic forces, arising from the interaction of Eddy currents induced in the metal by inductor magnetic field, cause an increased flow of the fluid, forced convection, more uniform temperature field and weak gravitation influence thus changing the conditions of solidification. The advantage of EMC reflects in obtaining a better quality of ingots compared to convent ional continuous casting process. Namely, the structure obtained is finer and more uniform through the cross section, with reduced segregation of alloy element and porosity. Apart from that, due to the reduced contact pressure (result of electromagnetic field effect) between the mould and the metal, the quality of ingot surface is improved, having no need for additional machine processing. The investigations conducted in the world were aimed to investigate the effect of electromagnetic, magnetic and hydrodynamic phenomena on Al ingots, but very little attention was given to the characterization of microstructure and mechanical properties. This work, should contribute to better knowledge of the effect of electromagnetic field on the obtained microstructure (morphology, size, volume fraction and distribution of phases) and properties of Al alloys. The chosen alloy was EN AW 7075 heat treatable, intended for forge with wide industry use. It is characterized by a number of defects that occur during the solidific ation process: porosity, hot cracks, non -uniformal grain size and crystal segregation. Since the quality of final product is directly affected by these defects it is necessary to prevent or reduce their appearance by the choice of the appropriate process and optimal parameters of casting. To compare the results of electromagnetic casting, (with different operating parameters), the process of vertical continual casting without the presence of low frequency electromagnetic field was selected. The results were obtained from microstructure and mechanical examination of Al alloy 7075 ingots casted with and without low-frequency electromagnetic field. The microstructure characterization shows that it is possible to obtain finer and more homogeneous microstructure through the entire cross section of ingots casted with electromagnetic field, compared to ingots casted without electromagnetic field. As the consequence of microstructure-mechanical properties correlation, the use of electromagnetic field improved the mechanical properties, as well. The results obtained from SEM/EDX, DTA,electrical conductivity measurement were also shoved and compared. The chemometric approach for mechanical properties prediction and numerical simulation of the forging process of EN AW 7075 alloy were carried out following the latest world trends and the obtained results can be used as a basis for further training by expanding of database of derived models. This doctoral dissertation is the investigation result of the project: “The development of casting technologies under the influence of electromagnetic field and technologies of hot plastic forming of 7000 series aluminium alloys for special purposes” TR34002, leaded by professor Zvonko Gulišija, in the frame of Technological Development Program, funded by The Ministry of Education, Science and Technological Development of the Republic of Serbia, in the period from 2011 to June 2016
The effect of different collectors on the quality of basic copper concentrate of the ore body Tenka
No full textThis paper presents the results of a part of technological tests, whose aim was to determine the optimum techno-economic conditions for the flotation concentration of ore from the deposit Tenka-3 - North Mining District, Copper Mine Majdanpek. The given view refers to testing the effects of collectors NaIPX, 3418 A and 5500 AP, as well as the pulp pH value on the quality of concentrate from the primary flotation process. It was found that the majority of copper, gold and silver in the primary concentrate is obtained using the collector AP 5500. In addition, a better quality of primary concentrate was obtained at higher pH values of pulp in the tested pH range (10.0 - 11.5)
Evaluation of the surfactant/phillipsite composites as carriers for diclofenac sodium
No full textIncorporation of diclofenac sodium into phillipsite modified with cetylpyridinium chloride (CP-Cl) or hexadecyltrimethyl ammonium bromide (HDTMA-Br) was followed by batch equilibrium adsorption studies in buffer solution at pH = 7.4. Characteristics of the drug/surfactant/zeolite complexes were investigated by UV/VIS, FTIR spectroscopy, thermal (DTA/TG) analysis and-potential measurements. The obtained data confirmed that organic cations at phillipsite surface were responsible for incorporation of diclofenac sodium. Diclofenac sodium incorporated amounts increased with increasing the amount of each surfactant as well as with increasing the initial drug concentration. Langmuir model was the best model for fitting the experimental data of diclofenac adsorption on surfactant/phillipsite composites, suggesting complex adsorption mechanism. The physico-chemical properties of surfactant/phillipsite composites and enhanced incorporation of diclofenac sodium suggests that it might be possible to use these materials as drug carriers
Reaction kinetics of mechanically activated cordierite-based ceramics studied via DTA
No full textSince cordierite, 2MgO center dot 2Al(2)O(3)center dot 5SiO(2) (MAS), is a very useful high-temperature ceramic material, it is important to decrease its sintering temperature. In order to accelerate the process of sintering, 5.00 mass% MoO3 was added to the starting mixtures. The mechanical activation of the starting mixtures was performed in a high-energy ball mill in time intervals from 0 to 160 min. After the activation, starting mixtures were sintered at 1300 A degrees C for 2 h. In order to determine the impact of mechanical activation on particle size distribution and powders morphology, the mechanically treated powders were characterized by a laser light-scattering particle size analyzer and scanning electron microscopy. The phase composition of the starting mixtures and sintered samples was analyzed by the X-ray diffraction method. In order to determine temperature intervals of chemical reactions and phase transitions, differential thermal analyses (DTA) and thermo-gravimetric analysis were used. Kissinger's equation was employed to calculate apparent activation energies of various processes that occur within the system during heating. Based on the obtained DTA results, it was established that mechanical activation along with MoO3 additive has influence on sintering temperature which was decreased for more than 100 A degrees C, comparing to the literature data