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Prediction of municipal solid waste generation using artificial neural network approach enhanced by structural break analysis
No full textThis paper presents the development of a general regression neural network (GRNN) model for the prediction of annual municipal solid waste (MSW) generation at the national level for 44 countries of different size, population and economic development level. Proper modelling of MSW generation is essential for the planning of MSW management system as well as for the simulation of various environmental impact scenarios. The main objective of this work was to examine the potential influence of economy crisis (global or local) on the forecast of MSW generation obtained by the GRNN model. The existence of the so-called structural breaks that occur because of the economic crisis in the studied period (2000-2012) for each country was determined and confirmed using the Chow test and Quandt-Andrews test. Two GRNN models, one which did not take into account the influence of the economic crisis (GRNN) and another one which did (SB-GRNN), were developed. The novelty of the applied method is that it uses broadly available social, economic and demographic indicators and indicators of sustainability, together with GRNN and structural break testing for the prediction of MSW generation at the national level. The obtained results demonstrate that the SB-GRNN model provide more accurate predictions than the model which neglected structural breaks, with a mean absolute percentage error (MAPE) of 4.0 % compared to 6.7 % generated by the GRNN model. The proposed model enhanced with structural breaks can be a viable alternative for a more accurate prediction of MSW generation at the national level, especially for developing countries for which a lack of MSW data is notable
Influence of different bonding and fluxing agents on the sintering behavior and dielectric properties of steatite ceramic materials
No full textThe focus of the study was on providing insights into interconnections between sintering and development of the crystalline microstructure, and consequently variations in dielectric behavior of four steatites fabricated from a low-cost raw material, i.e. talc. The changes, induced by the alternations of the binders (bentonite, kaolin clay) and fluxing agents (BaCO3, feldspar), were monitored in the temperature range 1000 degrees to 1250 degrees C in which complete densification and re-crystallization of the investigated structures were accomplished. The critical points in the synthesis of steatite materials were assessed by instrumental analyses. Crystallinity changes and mineral phase transition during sintering were monitored by X-ray diffraction technique. Microstructural visualization of the samples and the spatial arrangements of individual chemical elements were achieved via scanning electron microscopy accompanied with EDS mapping. The thermal stability was observed on the green mixtures using differential thermal and thermo gravimetric analyses. Electrical measurements recorded variations of the dielectric constant (epsilon(r)) and loss tangent (tan delta) as a function of the sintering temperature. The investigation highlighted critical design points, as well as the optimal combinations of the raw materials for production of the steatite ceramics for advanced electrical engineering applications
Agricultural wastes as low cost material for heavy metals removal
No full textRemoval of Pb(II), Cu(II) and Zn(II) from aqueous solutions by low cost agri-cultural wastes was investigated.
The effect of the initial pH value, biomass dosage, initial metal concentration and contact time was investigated in batch system. It is found that metal uptake increased with increasing the initial pH value, initial concentration and contact time but decreased with increasing biomass dosage. The optimum pH value for biosorp-tion process of the metal ions was found to be ranged from 5.0 to 6.0 for all inves-tigated materials.
The experimental data well fitted to the Langmuir isotherm model. The max-imum biosorption capacities of investigated agricultural waste materials followed the order: Pb(II) > Cu(II) > Zn(II). Kinetic data well fitted to the pseudo-second-order kinetic model. The kinetic study revealed that biosorption process is fast.
Desorption study was done due to of the need to recycle metal loaded mate-rials and dispose them. Obtained results revealed that investigated agricultural wastes after biosorption process can be efficiently recovered with diluted HNO3.
From obtained results and their comparison to different biosorbents reported in literature it can be concluded that investigated agricultural wastes can be used as natural, low cost, effective and ecofriendly materials for heavy metals removal from water solutions
Mechanism of polymetallic concentrate leaching with sulfuric acid and hydrogen peroxide solution
No full textThe determination of mechanism of the polymetallic concentrate leaching with sulfuric
acid and hydrogen peroxide was done based on the characterization of the starting
concentrate and leach residues. The application of XRD and thermal analysis on the
leaching mechanism determination was done. The phase content of concentrate and leach
residues were determined by X-ray analysis using diffractometer PHILIPS PW-1710. DTA
and TG analysis were performed in air atmosphere up to 1173 K on NETZSH, model 409
EP, device.
The polymetallic concentrate, used in experiments, has the following chemical
composition (in wt. %): Cu-8.92, Zn-8.79; Pb-12.66, Fe-19.80 and S-21.4. X-ray phase
analysis of the concentrate reveals that the sample contains chalcopyrite, sphalerite, galena
pyrhotite and quartz (Fig. a). On Fig. b the DTA and TG curves of polymetallic concentrate
are shown. Curves include two parts: first, a low temperature, which correspond to the
sulfides oxidation (the mass increase on the TG, and exothermic peaks on the DTA); and
second which correspond to the dissociation of sulphates and oxysulphates (the mass loss
on the TG, and endothermic peaks on the DTA).
The phases identified in the leach residue by XRD were elemental sulphur, anglesite,
chalcopyrite, sphalerite, galena pyrhotite and quartz (Fig. c), which confirms that the
elemental sulphur is formed during leaching. In Fig. d the TG-DTA curve of the leach
residue are shown. On DTA curve on the temperature of 118 oC, the endothermic peak as a
result of elemental sulfur melting is clearly visible. Then, in the range of 250-350 oC,
weight loss as a consequence of the oxidation of sulfur to SO2 gas occurs. The loss of mass
due to combustion of sulfur on Fig. d is smaller than the sulfide sulfur which is oxidized
during the leaching process, which indicates that the sulfur from sulfides is oxidised both
to the sulfate and to the elemental form. The mass increase followed by exothermic effects
in the range of 400-700 oC is a result of the oxidation of unleached sulphides in the solid
residues. At temperatures above 720 °C weight loss occurs as a result of dissociation of
sulphate and oxysulphates of lead, zinc, copper and iron with endothermic peaks on the
DTA curve. XRD and DTA/TG studies have contributed in determining the mechanism of
polymetallic concentrate leaching process in the system H2SO4-H2O2-H2O:CuFeS2 + 5/2H2O2 + 5/2H2SO4 = CuSO4 + 1/2Fe2(SO4)3 + 2S0 + 5H2O
(1)
CuFeS2 + 17/2H2O2 + 1/2H2SO4 = CuSO4 + 1/2Fe2(SO4)3 + 9H2O(2)
ZnS + H2O2 + H2SO4 = ZnSO4 + S0 + 2H2O (3)
ZnS + 4H2O2 = ZnSO4 + 4H2O (4)
PbS + H2O2 + H2SO4 = PbSO4 + S0 + 2H2O (5)
PbS + 4H2O2 = PbSO4 + 4H2O (6
Uticaj strukturno-teksturnih karakteristika sulfidnih mineralа na njihovo luženje iz polimetaličnog koncentrata rastvorom natrijum-nitrata i sumporne kiseline
No full textU radu su prikazani rezultati ispitivanja uticaja strukturno-teksturnih karakteristika sulfidnih
minerala na njihovo luženje iz polimetaličnog koncentrata rastvorom sumporne kiseline
i natrijum-nitrata. Za određivanja karakteristika sulfidnih minerala u polaznom koncentratu
i čvrstom ostatku luženja korišćena je hemijska, rendgenska difrakciona analiza na
polikristalnom uzorku (XRD), kvalitativna i kvantitativna mikroskopska i SEM/EDX analiza. U
polimetaličnom koncentratu je utvrđeno prisustvo halkopirita, sfalerita, galenita, pirotina i
minerala jalovine. Tokom luženja Pb–Zn–Cu sulfidnog koncentrata rastvorom natrijumnitrata
i sumporne kiseline, deo sulfidnih minerala ostaje neizlužen i zaostaje u čvrstim
ostacima luženja. Olovo, u obliku slaborastvornog olovo-sulfata (anglezita), ostaje u neizluženom
ostatku. Sadržaj sulfidnih minerala u neizluženom ostatku iznosi 35%, u kojem se
54,7% halkopirita, 31,9% sfalerita, 8,2% galenita i 37,6% pirotina javlja u vidu slobodnih
mineralnih zrna sa intenzivnom korozijom njihovih ivica i pojavom elementarnog sumpora
duž njihovih oboda. Strukturni sklop sulfidnih mineralnih zrna u polimetaličnom koncentratu
je povolјan i nije razlog prisustva neizluženih sulfidnih minerala u čvrstim ostacima
luženja. Razlog za to je elementarni sumpor koji nastaje u procesu luženja, taloži se na
površini sulfidnih mineralnih zrna i otežava kontakt sulfidnih minerala i sredstva za luženje.In this paper, the influence of structural and textural characteristics of sulfide
minerals on their leaching from a polymetallic concentrate by sulfuric acid and
sodium nitrate solution is presented. The starting material was Pb–Zn–Cu sulphide
polymetallic concentrate enriched during the flotation of a polymetallic ore
in the ″Rudnik″ flotation plant (Rudnik – Serbia). Leaching experiments were
carried out in a closed glass reactor, which provides stable hermetic conditions
and allows heating at constant temperature. Chemical, XRD, qualitative and
quantitative microscopic and SEM/EDX analyses were used to characterizes
samples of the polymetallic concentrate and leach residue. It was determined that
chalcopyrite, sphalerite, galena, pyrrhotite and quartz were present in the polymetallic
concentrate. The content of sulphide minerals was 69.5%, of which 60.9%
occurred as liberated grains: 88.3% of chalcopyrite, 59.3% of sphalerite, 25.1% of
galena and 51.6% of pirrhotite. The rest of chalcopyrite, sphalerite, galena and
pirrhotite grains were in the forms of inclusions, impregnations, and simple and
complex intergrowths. During the leaching process by sodium nitrate and sulphuric
acid solution, it was shown previously that the leaching rate of sulphide
minerals decreased with time while a part of the sulphide minerals remained in
the leach residue. After leaching at 80 °C for 120 min, the yields were 69.8, 82.7
and 67.1% for Cu, Zn and Fe, respectively. Lead, in the form of insoluble anglesite,
remained in the leach residue. In addition to the anglesite, unleached sulfide minerals
and quartz, elemental sulfur was found in the solid residue. The content of
sulphide minerals was 35% of which 33.7% minerals occur independently. In specific,
54.7% of chalcopyrite, 31.9% of sphalerite, 8.2% of galena and 37.6% of
pyrrhotite appear as separate grains with highly corroded surfaces. Therefore, the
structural assembly of sulphide grains in the polymetallic concentrate is favourable
and it is not the reason for the observed decrease in the leaching rate in the
final process stages. The obtained findings may be explained by the presence of
elemental sulphur that is formed during the reaction and precipitated at the grain
surfaces, thus creating a diffusion barrier for the leach solution
Luminescent Pr3+ doped fluorapatite nanoparticles with different excitation-emission profiles
No full textThe fluorapatite (FAP) nanoparticles doped with rear earth elements have been extensively studied as a potential luminescence inorganic material for in-vitro and in vivo cells and tissue bioimaging [1-3]. Luminescent nanoparticles of undoped and Pr3+ doped fluorapatite (Pr-FAP) have been successfully synthesized by co-precipitation method followed by calcination. Obtained materials are characterized by XRD, FTIR FAR, PLE-PL and SEM-EDAX methods, and theoretical prediction of structural changes was also done.
Emission of FAP nanoparticles occurs in violet-blue region of visible part of
spectrum under excitation in UV region. Introducing the Pr3+ into the lattice causes the red or blue shift depending of Pr3+ concentration and synthesis conditions. MCR-ALS analyses of fluorescence spectra and ab initio calculation indicated that Pr3+ ions are located in Pr-FAP lattice at Ca2 (6h) sites. Assumed mechanism of substitution of Ca2+ with Pr3+ ion is accompanied with charge compensation by incorporation of CO32- ions into the structure or by vacancies formation on metal ions position. Synthesized nanoparticles can be potentially used as a luminescent nanomaterials in biomedicine for targeting, bioimaging, drug delivery and therapy
Technological procedure for processing the quartz resources in order to obtain the assortment for water glass
No full textTests on quartz raw material from the deposit 'Bijela Stijena - Skočić' have included: grading, washing, grinding and magnetic separation. Test results have shown that the assortment of required sand quality can be obtained for water glass. The required quality condition for assortment of water glass, set by the company 'Alumina' Zvornik, is that Fe2O3 content does not exceed 0.04% and the grit of -0.4 + 0.05 mm. The results obtained after washing and grading starting sample used in these tests to a class of -0.4 + 0.05 mm showed that content of Fe2O3 from 0.131 % was reduced to 0.075%, and after treatment at high gradient electromagnetic separator at 0.038%. Microscopic analysis showed that the initial sample has: quartz, chalcedony, feldspar, mica, cherts, magnetite, limonite-goethite, shells, fossil remains, and that after the magnetic separation of magnetite sample was removed and most of the other carriers magnetic fraction. Based on this, a flow diagram is defined for procedure of obtaining the quartz sand for water glass on the basis of quartz raw materials from the deposit 'Bijela Stijena -Skočić'
Investigation the calcite hydrophobisation of different grain sizes
No full textThis paper presents the investigations of possibility of calcite hydrophobisation. Two samples of calcite of different size classes from the site 'Dobar kamen', Arandjelovac, Serbia, were used in the experimental work. Modifying the surface of calcite was carried out by stearic acid with 'dry' method. Concentrations of stearic acid in the modifying method were as follows: 0.3, 0.5, 0.8, 0.9, 1, 2, 2.5, 3 and 4%. The results showed that a complete hydrophobicity (I0=99.9%) of calcite sample with the medium diameter (d50) 10.87 μm was achieved at concentration of stearic acid of 0.8%, while for the sample with the mean grain diameter (d50) of 29.14 μm, it was achieved at concentration of stearic acid of 3%. These results were confirmed by the microscopic analysis
Correction: Nanomaterials environmental risks and recycling: Actual issues (2014, vol. 7, p. 1)
No full textUredništvo časopisa 'Reciklaža i održivi razvoj' je u dogovoru sa autorskim timom preglednog rada pod nazivom ' EKološki rizici i reciklaža nanomaterijala - aktuelna pitanja ' (D. Živković, Lj. Balanović, A. Mitovski, N. Talijan, N. Štrbac, M. Sokić, D. Manasijević, D. Minić, V. Ćosović), koji je publikovan u ovom časopisu vol.7 iz 2014. godine (str.1-8), donelo odluku da se zbog uočenog ozbiljnog previda (na osnovu provere CEON-a), koji se ogleda u neadekvatnom citiranju jedne reference, odnosno izostavljanju reference iz koje su korišćeni pojedini tekstualni navodi, kao i dupliranja pojedinih referenci, izvrši neophodna ispravka onih delova rada u kome pomenuti referentni izvor nije adekvatno naveden, kao i ispravke u listi referenci, a u skladu sa propisanom procedurom.Editorial board of the 'Recycling and Sustainable Development' Journal in agreement with the authors of the article titled 'Nanomaterials environmental risks and recycling - actual issues' (D. Zivkovic, Lj. Balanović, A. Mitovski, N. Talijan, N. Strbac , M. Sokić, D. Manasijević, D. Minić, V. Ćosović), which was published in this journal vol. 7 in 2014 (p. 1-8), made the decision to do correction of article because of a perceived serious oversights (based on check out by CEON). Oversight is reflected in inadequate citing a reference, or omission of reference from which the text used by individual states, as well as the duplication of certain references. The necessary correction refers to the parts of the article which reference source is not adequately specified and updates the list of references, in accordance with prescribed procedure
Effect of la2o3 on the structure and the properties of strontium borate glasses
No full textThe selected lanthanum-strontium borate glasses were prepared by a conventional melt-quenching technique. The compositions of the investigated glasses were chosen to be: 5.7, 9.5, 14.3, 19.1 mol% for La2O3, 22.9, 19.1, 14.3, 9.5 mol% for SrO and 71.4 mol% for B2O3. The density, molar volume, oxygen molar volume, oxygen packing density, oxygen/boron ratios and structural transformations in the glass network were investigated according to the substitution of SrO by La2O3. The density and the molar volume increased in parallel with La2O3 content increase. Simultaneously, oxygen molar volume values increased while the oxygen packing density values decreased. A hot stage microscope (HSM) and a differential thermal analysis (DTA) were used to determine the characteristic temperatures. By increasing the content of lanthanum, the glass transition temperatures, changed with the same trend as the molar volume. Glass stability parameters were calculated from the temperatures obtained by DTA and HSM. The HSM results were used to obtain the viscosity curves by applying the Vogel-Fulcher-Tamman (VFT) equation