ritnms
Not a member yet
1551 research outputs found
Sort by
Eco-materials for soil remediation based on polyphosphate glasses
No full textIn this paper the results of examination of the dissolution process of the polyphosphate glass 45P2O5×25K2O×15CaO×10MgO×3SiO2×ZnO×MnO [mol%] in 2% citric acid at temperatures of 15, 20 and 30 ºC were presented. The dissolution experiments were performed on glass powder grain size of 0.1-0.3 mm and 0.3-0.65 mm. The mass loss of glass, normalized concentration of PO43+ and K+ ions and the conductivity of solution (χ) as a function of leaching time was determined. It was revealed that for short reaction times, the changes of normalized mass loss (fm) are linear with time and the rates of glass dissolution under given conditions are highest. By increasing the dissolution time the dissolution rate of glass decreased. The initial release rates r0 (PO43-) = 3.550 [g/m2h] and r0 (K+) = 2.133 [g/m2h] at t = 300C were calculated for glass powder sample 0.3-0.65mm. The dissolution process in citric acid is complex and can be explained by hydration reaction and hydrolysis, leading to the disruption of phosphate chains which form the structure of glass. The results of the dissolution experiments indicated that this glass can be used as an eco- fertilizer in soil remediatio
Thermodynamics and characterization of shape memory Cu-Al-Zn alloys
No full textThe thermodynamic properties and the microstructure, hardness and electrical conductivity of shape memory alloys (SMAs) belonging to ternary Cu-Al-Zn system were studied by Muggianu model and experiment, respectively. The isothermal section of phase diagram at 293 K was calculated using Thermo-Calc software. Experiments were conducted by X-ray diffraction, light optic microscopy, scanning electron microscopy with energy dispersive X-ray spectrometry, hardness and electrical conductivity measurements. The calculated values of thermodynamic properties indicate that Cu shows good miscibility with Al and Zn in all investigated alloys. The microstructural analysis of samples reveals that the structure consists of large and polygonal grains
Application of exergy analysis in recycling streams
No full textMaterijali za recikliranje uvek sadrže izvestan stepen nečistoća. Prisustvo nečistoća tj. kontaminacija u reciklažnim tokovima izaziva promenu u izvornom sastavu materijala za reciklažu. Usled toga, kvalitet materijala može se smanjivati u svakom narednom koraku reciklaže. Pored toga, resursi nižeg kvaliteta proizvedeni su iz resursnih tokova koji su u izvornom obliku imali viši kvalitet. Ovakvi gubici kvaliteta ne mogu da se mere masenim bilansima, isto kao što se degradacija kvaliteta ne može prikazati samo merenjem mase. Za proračun svih gubitaka prouzrokovanih reciklažnom kontaminacijom, svi dalji procesi reciklaže potrebni da bi se materijali vratili nazad u resursne cikluse moraju biti uključeni. U ovom radu prikazan je metod za izračunavanje eksergijskog sadržaja i eksergijskog gubitka metalnih rastvora u toku iskorišćnja i reciklaže. Gubici pripisani reciklaži ili tačnije materijalni gubici, gubici usled kontaminacije drugim metalima i posledično potreba za razblaživanjem, mogu se koristiti kao indikatori gubitka kvaliteta materijala i efikasnosti korišćenja resursa u proizvodnim sistemima. Dakle, ovde je eksergija predložena kao mera efikasnosti korišćenja resursa. U radu su proračuni eksergijskih gubitaka tokom reciklaže prikazani na primeru aluminijumskog otpada.Materials for recycling always contain a certain degree of contamination. The presence of impurities i.e. contamination in the recycling streams causes a change in the composition of the original materials to recycle. As a result, the quality of materials can be reduced in each successive step of recycling. In addition, the resources of lower quality are produced from the resource flows which had a higher quality in their original form. This kind losses of quality cannot be measured by mass balance, as well as the quality degradation not only can display measurements of mass. For the calculation of all losses caused by recycling contaminations, all further recycling processes required to return the materials back into resource cycles must be included. The method for calculating the exergy content and exergy losses of metal solutions during recovery and recycling is presented in this paper. The losses attributed to recycling, namely the material losses, the contamination losses with other metals, and the consequent need for dilution can be used as indicators of the quality loss of materials and of the efficiency of resource use in product systems. Therefore, exergy is proposed here as a measure of the efficiency of resources use. This paper presents calculations of exergy losses during recycling shown in the case of aluminum waste
Microbial solubilization of phosphorus from phosphate rock by iron-oxidizing Acidithiobacillus sp B2
No full textProcedures for solubilization of phosphorus from insoluble phosphates by acidophilic autotrophs and heterotrophs are considered to be research subjects of great importance in sustainable soil management, and could become, in the future, an alternative to current expensive methods of industrial fertilizer production. Furthermore, this biological production of fertilizer can be considered to be more environmentally friendly than current production methods. The object of this study was to investigate the possibility of phosphorus leaching from phosphate rock apatite using sulphuric acid generated from pyrite by iron-oxidizing Acidithiobacillus sp. B2, and to test the possible application of the mixture of these two minerals to produce a natural phosphate fertilizer. Iron-oxidizing Acidithiobacillus sp. B2 was isolated from copper sulphide mine wastewater (Lake Robule) in Bar, Serbia. The bacterium was identified by 16SrDNA oligonucleotide sequence and characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). The leaching experiment was carried out in laboratory conditions at 28 degrees C for a period of four weeks. The results showed that up to 34.5% of the inorganic phosphorus was leached from the test mixture when in suspension with iron-oxidizing Acidithiobacillus sp. B2, while at the same time, the degree of leaching from a control suspension (without iron-oxidizing Acidithiobacillus sp. B2) was only up to 3.8%. Due to its low cost and environmental acceptance, treatment of soil with phosphate minerals in combination with pyrite and acidophilic iron- and sulphur-oxidizing bacteria could become an attractive and alternative way to improve the quality of alkaline soils
Influence of hidrofobized limestone as a filler on the mechanical properties of PVC
No full textThe results have shoun that the break force in the "wet" process increases with 1.51kN for PVC+C at 1.63 kN, in a sample of PVC+CS-3, which is a completely hydrophobized. In the "dry" process, the breaking force increases from 1.51kN in PVC+C to 1.55kN in PVC+CD-3. Breaking limit increases with degree of hydrophobization and the "wet" process from 36.72 MPa in PVC+C to38.17MPa in PVC+CS-1.5 and further to 39.89 MPa in a sample of PVC+CS-3. In the “dry” process, the breaking limit grows from 36.72 MPa for PVC+to 38.26MPa in a sample of PVC+CD-3 with coating degree of 99.90%. Strenght limit also changes with coating degree (hydrophobization), while the strength force remains almost unchanged in both procedures
Modified corn silk as biosorbent for Pb(II) ions removal from aqueous solution
No full textIn this work, corn silk was chemically modified by 0.5 M HNO3 and used as biosorbent for removal
of Pb (II) ions from aqueous solutions. The effect of biosorbent dosage was studied in batch experiments with
25 mL of aqueous lead solution of concentration 200 mg/L, at pH 5, 120 min of contact time and room
temperature. The modified corn silk was characterized by pHPZC The maximum biosorption capacity was found
to be 39.5 mg/g at 0.025 g of biosorbent dosage. The biosorption capacity decreased with increasing of
biosorbent dosage
Primenа otpаdne biomаse zа sprečаvаnje negаtivnog efektа klimаtskih promenа
No full textŠiroko dostupna, obnovljiva, i praktično besplatna, otpadna biomasa je važan resurs jer se može iskoristiti kao energent i material ciljnih karakteristika poput biosorbenta organskih i neorganskih polutanata, korektora zemljišta, organskog đubriva, u proizvodnji papira, tekstila itd. Ukoliko se ova biomase konvertuje u energiju tada zamenjuje fosilna goriva, smanjuje emisiju gasova staklene bašte i obezbeđuje obnovljivu energiju zemljama u razvoju. Sve učestalije poplave i suše usled klimatskih promena, dovode do zagađenja podzemnih voda, zemljišta i vazduha teškim metalima. Već izvesno vreme, biosorpcija predstavlja obećavajuću biotehnologiju za uklanjanje polutanata i/ili povraćaj iz rastvora primenom biosorbenata.
Otpadna biomasa može da se konvertuje u korisne agro-ekološke proizvode pri čemu dolazi do povećanja dobiti cele obrade, smanjenja negativnog uticaja na klimatske promene i do većeg iskorišćenja biljnog materijala
Thermally induced phase transformation of Pb-exchanged LTA and FAU-framework zeolite to feldspar phases
No full textThermally induced phase transformations of Pb-exchange LTA and FAU zeolites were from ambient temperature to 1300 °C. Both frameworks collapse into amorphous intermediate products after heating between 600 and 650 °C. Prolonged heating of the intermediate product over 1100 °C results in the formation of disordered Pb-feldsparLTA [a = 8.414 (4) Å, b = 13.048 (4) Å, c = 7.169 (4) Å, β = 115.35° (3)] and Pb-feldsparFAU [a = 8.422 (4) Å, b = 13.054 (4) Å, c = 7.173 (4) Å, β = 115.37° (3)] phases. The phase conversions within the investigated temperature range were followed by thermal (DTA, TGA, and DSC), XRPD, and Raman methods
Recovery of copper, gold and silver from ore deposit Tenka-3 in dependence on grinding fineness
No full textThe results shown in this paper represent a part of technological testings performed to evaluate the possibility of copper and precious metals valorization from ore deposit Tenka 3. Concentration of useful minerals was achieved through flotation method including rougher and scavenger circuits. During the experimental procedure AEROPHINE 3418A Promoter (phosphine- based collector) and AERO 5500 Promoter (ethoxycarbonyl thiourea based collector) were used for the hydrophobization of mineral surfaces. pH value of flotation pulp was 10.5 in every experiment. Grinding fineness varied from 56% to 65% of class –0.074 mm. The highest recoveries of copper and precious metals are obtained at grinding fineness of 60% –0.074 mm, while the highest grades are obtained at grinding fineness of 56% –0.074 mm
Usage of the fine grained limestone for neutralization of acid soil- application of pelletizing metods
No full textThe rapid progress of industry, worldwide, as well as here, results in increasing of acid soil. According to some researches, about 60% of our soil is acid and requires neutralization that is done by the means of grinded limestone, what is customary. Its inconvenience for use in this shape regarding the atmospheric conditions, particularly-the wind inspired our attempts to agglomerate it. By the process of pelletizing, limestone can be successfully pelletized into size as chemical fertilizers