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Effects of SA surface treatment on the properties of CaCO3 used as filler in construction composites
No full textCalcium carbonate (CaCO3 ) is mineral filler that has been most extensively used in the construction composites as well as in the polymer industry. Coarse CaCO 3 grains can be easily incorporated into the composite material, but the smaller-sized particles tend to agglomerate due to the enhanced particle-to-particle interactions, which leads to serious performance problems. The most efficient way of surpassing this problem is to enhance the final composite properties by surface treatment of the filler with a surfactant. Following such procedure a water-repellent construction composites are obtained (i.e. reparation mortars, mortars for the exterior works, thin coatings for concrete walls, etc.). The stearic acid is a universal and economical surfactant which is often used to improve CaCO3 hydrophobic properties. This study investigates and subsequently compares the surface and mechanical properties of untreated ground calcium carbonate powder and treated powder with stearic acid using a dry process coating system. The CaCO 3 powder (grain size class: -200 + 63 μm) was pulverized in a laboratory Retsch-ZM-1 mill with a 250 μm mesh size sieve and a peripheral comminuting path. The surface of CaCO3 powder is generally hydrophilic, but it was changed to a hydrophobic surface when coated with SA. The coating procedure was conducted in following manner: 1% of SA was added to the CaCO3 powder which was previously thermally treated at 120°C for 2 hours, and the mixture was stirred in a laboratory mixer with 1500 rpm. The surface treatment decreases the intensity of particle-to-particle interaction and increase adhesion of filler. There has been extensive research reporting about the effects of stearic acid surface treatment on the physical properties and thermal behavior as well as mechanical properties of CaCO3 composites. The contact angle of water on the coated calcium carbonate powder surface and hydrophobicity are increased with increasing concentration of SA. As a result, thermal stability and mechanical properties of the composite were increased compared to untreated CaCO3 composites. The influence of surface treatment of the particles, with and without stearic acid on the mechanical, thermal and structural properties was studied. The experiments included mechanical and physical testing; differential thermal analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The composite systems containing coated CaCO3 were found to exhibit better mechanical properties as compared to composite systems containing uncoated CaCO3
Heavy metals removal from aqueous solution by biosorbent based on apricot stones waste biomass
No full textU okviru ove doktorske disertacije ispitana je mogućnost upotrebe biosorbenta na bazi endokarpa koštica kajsije Prunus armeniaca L. u svrhu uklanjanja Cu(II), Zn(II) i Pb(II) jona iz vodenih rastvora. Koštice kajsija (KK) su poreklom iz fabrike za preradu sokova „Vino Župa” iz Aleksandrovca, gde su klasifikovane kao otpadni materijal iz procesa prerade voća. U cilju dobijanja biosorbenta sa što boljim sorpcionim karakteristikama KK je tretiran rastvorom NaOH. Serijom eksperimenata odabrani su optimalni parametri modifikacije (početna koncentracija NaOH 1 mol/L; odnos čvrsto/tečno 1:20; vreme kontakta 180 minuta) i dobijen je modifikovani materijal KKM. Izvršena je karakterizacija i upoređivanje KK i KKM. Rezulatati hemijskih analiza su potvrdili da je posledica baznog tretmana razlaganje hemiceluloze (19,23 i 3,52% kod KK i KKM, respektivno), što su i FT-IR spektri potvrdili (pik na 1730 cm-1, koji ukazuje na -C=O vezu koja potiče od estarske grupe u hemicelulozi, se kod KKM gubi). Takođe, bazni tretman je doveo do uklanjanja masti i voskova sa površine biomaterijala, što je potvrđeno hemijskom analizom i FT-IR i SEM analizama. Posledica baznog tretmana je i povećanje tačke nultog naelektrisanja i promena odnosa količine kiselih i baznih grupa na površini KKM. Kod KK sadržaj ukupnih kiselih grupa je veći u odnosu na KKM (1,619 mmol/g i 0,317 mmol/g, respektivno), dok je kod KKM obrnuto: sadržaj ukupnih baznih grupa je veći nego kod KK (0,309 mmol/g i 0,037 mmol/g, respektivno). Rezultati živine porozimetrije su potvrdili da je nakon baznog tretmana kod KKM došlo do povećanja zapremine pora (sa 218 na 270 mm3/g), povećanja prosečnog prečnika pora (sa 393 na 468 nm) i poroznosti (sa 25 na 30 %). KKM je ispitan kao biosorbent za uklanjanje Cu(II), Zn(II) i Pb(II) jona iz vodenih rastvora. Ispitani su osnovni parametri koji utiču na proces biosorpcije (pH, kontaktno vreme, koncentracija biosorbenta, granulacija)...In this doctoral thesis, use of apricot (Prunus armeniaca L.) stone endocarp as possible biosorbent for the removal of Cu(II), Zn(II) and Pb(II) ions from aqueous solution was examined. Apricot stones are from “Vino Župa” Inc. Aleksandrovac where it is classified as a waste product from fruit processing. In order to get biosorbent with highest sorption performances this waste material was treated with solution of NaOH. In a series of experiments optimal modification parameters were determined (initial concentration 1mol/L NaOH; solid/liquid ratio 1:20; contact time 180 minutes) and modified material was obtained (KKM). Characterization and comparison of both material, native (KK) and modified (KKM), was performed. Results of chemical analysis as well as FT-IR spectra, showed that disintegration of hemicellulose occurs as a result of alkaline treatment (decrease of hemicellulose content from 19.23% in KK to 3,52% in KKM; FT-IR spectrum shows loss of 1730 cm-1 peak in KKM, that shows -C=O group in hemicellulose). FT-IR and SEM analysis showed that with alkaline treatment wax and oils are removed from the surface of the biomatirial. Point of zero charge also rose as a consequence of alkaline treatment. Concentration of total acidic groups is higher in KK than in KKM (1.619 mmol/g and 0.317 mmol/g, respectively), while in KKM total concentration of basic groups is higher than in KK (0.309 mmol/g and 0.037 mmol/g, respectively). Results of porosimetry confirmed that after alkaline treatment pore volumes increased in KKM (from 218 to 270 mm3/g), as well as pore diameters (from 393 to 468 nm) and porosity (from 25 to 30%). KKM was examined as a biosorbent for removal of Cu(II), Zn(II) and Pb(II) ions from water solutions. Parameters that affect biosorption were triald (pH, contact time, concentration of biosorbent, granulation) and optimum values for each parameter were established: pH=5,0; contact time 120 minutes; solid/liquid ratio 0,1g/50mL; granulation LT 0,8mm..
Characterization and usefulness of corn cob as biosorbent for Pb2+, Cu2+ and Zn2+ ions removal from aqueous solutions
No full textCilj ovog rada je ispitivanje mogućnosti upotrebe oklaska kukuruza za uklanjanje teških metala iz vodenih rastvora. Svi biosorpcioni eksperimenti izvođeni su u šaržnom sistemu. Karakterizacija biosorbenta izvršena je termijskom analizom (DTA/TGA), metodom skenirajuće elektronske mikro-skopije i energijsko-disperzivne rendgenske analize (SEM-EDX) i infracrvenom spektroskopijom sa Furijeovom transformacijom (FTIR). Na osnovu FTIR analize oklaska kukuruza pre i nakon uklanjanja Pb2+, Cu2+ i Zn2+ jona, ustanovljeno je da jonska izmena i hemisorpcija učestvuju u procesu biosorpcije jona metala na oklasku kukuruza. Eksperimentalni rezultati obrađeni su Lengmirovim i Frojndlihovim modelom izotermi. Maksimalni adsorpcioni kapacitet oklaska kukuruza za Pb2+, Cu2+ i Zn2+ iznosi 5,59; 2,62 i 1,23 mg/g, respektivno. Nakon ispitivanja procesa desorpcije zaključeno je da se adsorbovani joni metala na oklasku kukuruza efikasno i lako mogu ukloniti rastvorom HNO3. Rezultati ovog istraživanja ukazuju da se oklasak kukuruza može primeniti kao potencijalni biosorbent za uklanjanje Pb2+, Cu2+ i Zn2+ jona iz vodenih rastvora.The objective of this study was to investigate corncob as biosorbent for heavy metals removal from aqueous solutions. All biosorption experiments were performed in batch system. The biosorbent were caracterized by thermal analysis (DTA/TGA), Scanning Electron Microscopy and Energy Disperzive X-Ray analysis (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. FTIR analysis of corn cob before and after Pb2+, Cu2+ and Zn2+ removal from aqueous solutions showed that ion exchange and chemisorption were involved in biosorption process of metal ions on to corn cob. Experimental data were fitted by Langmuir and Freundlich isotherm models. Maximum adsorption capacity of corn cob for Pb2+, Cu2+ and Zn2+ were 5,59; 2,62 i 1,23 mg/g, respectively. Desorption study showed that metal adsorbed corn cob can be effectively regenerated by HNO3 solution. Results from this study indicated that corn cob can be used as potential biosorbent for Pb2+, Cu2+ and Zn2+ removal from aqueous solutions
Removal of uranium (VI) from aqueous solution by acid modified zeolites
No full textCilj ovog rada je prikaz mogućnosti primene prirodnog i modifikovanog zeolitskog minerala kao adsorbenta i materijala za sanaciju voda kontaminiranih uranijum jonom. Modifikovani uzorci zeolita dobijeni su tretiranjem prirodnog zeolita - klinoptilolita sa kiselinama: hlorovodoničnom, oksalnom i limunskom. Polazni i modifikovani zeoliti su okarakterisani hemijskom analizom, skenirajućom elektronskom mikroskopijom (SEM), rendgenskom analizom (XRPD), IC spektroskopijom, termičkom (TG/DTA) analizom i određivanjem kapaciteta katjonske izmene, a polazne i neadsorbovane količine uranijum jona su određene fluorimetrijski. Eksperimenti su sprovedeni da se ispita uticaj odnosa čvrsto/tečno, pH i vremena na adsorpciju uranijum jona na zeolitu. Utvrđeno je da tretman sa kiselinama zeolita povećava adsorpciju uranijum jona. Najviši indeks adsorpcije imao je uzorak zeolita modifikovan sa hlorovodoničnom kiselinom. Dobijeni rezultati adsorpcije na H-zeolitu su izračunati prema Langmirovom modelu.The objective of this study was the review of natural zeolite, modified with acid, as a candidate material for the remediation of groundwater contaminated by uranium(VI). The modified zeolite samples were obtained by treatment of natural zeolite - clinoptilolite with acids: hydrochloric, oxalyc and citric. Starting and modified zeolites were characterized by chemical analysis, SEM, XRPD analysis, IR spectroscopy, thermal (TG/DT) analysis and by determination of cation exchange capacity, while starting and nonadsorbed amounts of uranium(VI) ion were determined by fluorometric method. Batch experiments were conducted to investigate the effect of solid/liquid ratio, pH and time on the U(VI) uptake by zeolite. Modification of zeolitic tuff with acids significantly increased adsorption of uranium(VI). The highest adsorption of uranium(VI) ion was achieved on clinoptilolite modified with hydrochloric acid. Uranium(VI) adsorption data for zeolite modified with hydrochloric acid was fitted to the Langmuir model
Influence of mechanical activation on MgO-Al2O3-SiO2 system in the presence of TeO2 additive
No full textOva istraživanja posvećena su uticaju mehaničke aktivacije na strukturu kordijeritne smeše 2MgO+2Al2O3+5SiO2. Praćena su i testirana dva paralelna sistema, jedan bez, i drugi u prisustvu 5 masenih % TeO2 kao aditiva. Mehanička aktivacija prahova vršena je u visoko energetskom mlinu sa kuglama u vremenskom intervalu od 0 do 40 minuta. Tokom aktivacije došlo je do reakcije polaznih komponenti u čvrstoj fazi, pri čemu su nastala intermedijarna jedinjenja. Metoda rendgenske difrakcije je korišćena radi identifikacije faznog sastava tokom reakcije, dok su SEM i PSA metode korišćene za praćenje promene morfologije mehanički tretiranih prahova. Cilj aktivacije polaznih prahova je sniženje temperature i mogućnost da se skrati vreme trajanja procesa sinterovanja u postupku dobijanja krajnjeg proizvoda.Cordierite 2MgO+2Al2O3+5SiO2 is frequently used ceramic material, that is commonly used as a carrier of electrical components due to its low dielectric constant (~ 5), and low temperature thermal expansion coefficient (20·10-7 oC-1). In order to accelerate the process of sintering, 5.00 mass% TeO2 was added to the starting mixtures. System was tested in two parallel mixtures, one with no additives, and the other one with TeO2. The mechanical activation of the both mixtures was performed in a highenergy ball mill in time intervals from 0 to 40 min with ball to powder mass ratio 1:40. The particle size analysis (PSA) was employed in order to determine the changes in the particle size of the mechanically treated powders. The phase composition of the starting powders as well as microstructures was analyzed by the means of X-ray diffraction method and SEM
Selected heavy metal biosorption by compost of Myriophyllum spicatum-A chemometric approach
No full textIn this study adsorption characteristics of lead, copper, cadmium, nickel and zinc ions onto the compost of Myriophyllum spicatum were examined. The effects of sorbent dose, duration of sorption and solution concentration on the sorption of heavy metals have been investigated. Scanning electron microscope (SEM) and thermogravimetric and differential thermal analysis (TG-DTA) were used for the characterization of this biosorbent. Low coefficients of variation have been obtained for each applied assay, which confirmed the high accuracy of measurements. Principal component analysis (PCA) was applied for differentiation of samples. Mathematical models (form of second order polynomials) were developed for prediction of adsorption. Score analysis is being useful for accessing the effect of process parameters and the tool for determination of sorption quality. On the basic of experimental results and model parameters, it can be concluded that compost has a high biosorption capacity can be utilized for the removal of selected metals from wastewater
Modeling and Prediction of the end of Life Vehicles Number Distribution in Serbia
No full textThe impact of various time-defendant factors on the recycling rate of end-of-life vehicles (ELV) in Republic of Serbia was investigated. Statistical distribution of the frequency of the number of ELV in the year of dismantling depending on the year of production of ELV is designed using the two-parameter Weibull distribution function and MATLAB software, based on a real time data. Obtaining the time-dependence of Weibull parameters, a statistical distribution of frequency of the number of ELV in the coming period in Serbia was simulated. These results in combination with amount of materials in the most abundant cars in Serbia were used to simulate the overall amount of materials, which are available for recycling, in the coming period. These results are essential for automotive recycling industry management, particularly for shredders, dismantlers and metal pre-processors
Alkali modified hydrochar of grape pomace as a perspective adsorbent of Pb2+ from aqueous solution
No full textHydrochar produced via hydrothermal carbonization of grape pomace was considered as novel sorbent of Pb2+ from aqueous solution. In order to enhance the adsorption capacity, hydrochar was chemically modified using 2 M KOH solution. Both materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction technique. Batch experiments were performed to examine the effect of sorbent dosage, pH and contact time. Obtained results showed that the KOH treatment increased the sorption capacity of hydrochar from 27.8 mg g(-1) up to 137 mg g(-1) at pH 5. Adsorption of lead 'on either of the materials was achieved through ion-exchange mechanism, chemisorption and Pb2+-Tr interaction. The Sips isotherm model gave the best fit with the experimental data obtained for Pb2+ sorption using activated hydrochar. The adsorption kinetic followed a pseudo second-order model. Thermodynamic parameters implied that the Pb2+ binding for hydrochar surface was spontaneous and exothermic process. Findings from this work suggest that the hydrothermal carbonization is a promising route for production of efficient Pb2+ sorbents for wastewater treatment
Corn cob and corn silk as biosorbent for metal ions removal from aqueous solution: comparative analysis
No full textIn this work, corn cob and corn silk were used as biosorbent for removal of Pb2+, Cu2+ and Zn2+ ions
from aqueous solutions. Adsorption experiments were performed in batch mode. Corn cob and corn silk were
characterized by scanning electron microscopy (SEM). The maximum biosorption capacities of corn cob was
found to be 0.049, 0.053 and 0.021 mmol L-1 for Pb2+, Cu2+ and Zn2+ ions, respectively. At the other hand,
higher values of maximum biosorption capacities: 0.40, 0.22 and 0.19 mmol L-1 for Pb2+, Cu2+ and Zn2+ ions,
respectively, indicates that corn silk has better adsorption characteristics in comparison to corn cob
Recycling of platinum from crucibles for melting and casting
No full textThe aim of this study was the recycling of platinum from crucibles for melting and casting. This paper has considered the possibility of direct melting of crucibles as well as the possibility of processing the crucibles by PMS methods (shaking table and flotation concentration). Laboratory studies have shown that leaching of ground crucibles in sulfuric acid has achieved the leaching degree of magnesium oxide of 99.98% thus providing a material suitable for melting