The development of methods for analysis of halogen elements in solid samples in oxygen atmosphere

Analiza kvaliteta ĉvrstih materijala, u zavisnosti od namene, obuhvata: tehniĉku analizu, elementarnu analizu, analizu makrokomponenata i mikrokomponenata. Poseban analitiĉki zadatak predstavlja analiza anjona u sloţenoj matrici ĉvrstog uzorka. U literaturi i analitiĉkoj praksi postoji veliki broj metoda za odreĊivanje halogenih elemenata, od klasiĉnih do savremenih (instrumentalnih), koje se razlikuju kako po principima rada, tako i po kriterijumima koji karakterišu analitiĉke tehnike, od kojih treba izdvojiti taĉnost i reproduktivnost. Predmet rada ove doktorske disertacije su halogeni elementi u uglju. Halogeni elementi u uglju su prisutni u niskim koncentracijama, ali je uticaj ovih elemenata na ţivotnu sredinu i zdravlje ljudi od posebnog znaĉaja. Istraţivanja u okviru ove disertacije obuhvataju analizu halogenih elemenata u uglju, rezultate istraţivanja pirohidrolitiĉke metode za odreĊivanje halogenih elemenata, kao i primenu eksperimentalnog dizajna za razvoj analitiĉkih metodologija. Cilj ove doktorske disertacije bio je da se utvrdi metodologija i odrede uslovi za istovremeno odreĊivanje fluora, hlora i broma u uglju. U okviru ove disertacije primenjene su statistiĉke metode za organizaciju i izvoĊenje eksperimenata, i tehnike za obradu i analizu dobijenih rezultata. Primenom frakcionisanog faktorijskog dizajna ispitan je uticaj šest promenljivih na sagorevanje uglja u kiseoniĉnoj bombi i apsorpciju gasovitih jedinjenja koja se tokom sagorevanja izdvajaju iz uglja. Ispitan je uticaj poĉetnog pritiska kiseonika, dodatak katalizatora i pomoćnog goriva na sagorevanje uglja, kao i tip apsorpcionog rastvora, dodatak redukcionog agensa i vreme hlaĊenja bombe nakon sagorevanja na apsorpciju gasovitih jedinjenja. Koncentracija jona u apsorpcionom rastvoru merena je potenciometrijski jon-selektivnom elektrodom (za fluorid-jon) i jonskom hromatografijom. Rezultati frakcionisanog faktorijskog dizajna su analizirani pomoću Pareto-grafika, grafika glavnih efekata i dijagrama interakcije parametara. UtvrĊeno je da se dodatkom katalizatora i povećanjem pH vrednosti apsorpcionog rastvora smanjuje koncentracija halogenid-jona u apsorpcionom rastvoru. S druge strane, povećanjem poĉetnog pritiska kiseonika i dodatkom pomoćnog goriva, povećava se izdvajanje halogenih elemenata iz uglja tokom sagorevanja u atmosferi kiseonika. Na osnovu rezultata preliminarnih istraţivanja, pritisak kiseonika i zapremina pomoćnog goriva su detaljnije ispitani primenom metodologije odgovora površine. Rezultati optimizacionih eksperimenata razmatrani su analizom grafika odgovora površine, procene regresionih koeficijenata i analize varijansi. Pošto su se optimalni uslovi za odreĊivanje fluora i hlora razlikovali, definisan je grupni parametar - ukupni halogeni u uglju (engl.- total halogen in coal, TCX). Ukupni halogeni u uglju su izraţeni preko hlora, a hlor je izabran iz razloga što predstavlja dominantan halogeni element u uglju. Optimalni uslovi metode odreĊivanja ukupnih halogena u uglju sagorevanjem u kiseoniĉnoj bombi su: pritisak kiseonika od 2,5 MPa, zapremina pomoćnog goriva od 150 µL, apsorpcioni rastvor je voda uz dodatak 0,5 % rastvora vodonik-peroksida i hlaĊenje kiseoniĉne bombe u ledenom kupatilu 15 minuta nakon sagorevanja uglja. Masa uzorka je bila 0,5 g. Validacija predloţene metode za odreĊivanje fluora i hlora sagorevanjem u kiseoniĉnoj bombi uraĊena je analizom internih referentnih uzoraka uglja i sertifikovanih referentnih ugljeva (BCR 460 i NIST 1632c). Relativna standardna devijacija odreĊivanja fluora bila je manja od 5,0 %, a procenat izdvojenog fluora u odnosu na referentnu vrednost veći od 95 %. Relativna standardna devijacija odreĊivanja hlora bila je manja od 6,0 %, a procenat izdvojenog hlora veći od 85 %, što znaĉi da je odreĊivanje fluora i hlora predloţenom metodom precizno i reproduktivno. Predloţenom metodom je odreĊen i sadrţaj sumpora u uglju. Validacija metode za odreĊivanje sumpora je pokazala da je standardna devijacija merenja manja od 6 %, uz dobru ponovljivost.Comprehensive analysis of the quality of solids, depending on the application, includes: technical analysis, elemental analysis, analysis of the macrocomponents and microcomponents. A special analytical task is the analysis of anions in a complex matrix of solid samples. In literature and in analytical practice there are a number of methods for the determination of halogens, from classic to contemporary (instrumental), which differ according to the principles of work, and according to criteria that characterize the analytical techniques of which accuracy and reproducibility should be allocated. The subject of the work of this doctoral thesis are halogen elements in coal. Halogen elements in coal are present in low concentrations, but the impact of these elements on the environment and human health is of particular importance. Research in this thesis are designed in the field of analysis of the halogen elements in coal, the results of pyrohydrolityc methods for the determination of halogens, as well as on the application of experimental design for the development of analytical methodologies. The aim of this doctoral thesis was to establish methodology and determine the conditions for simultaneous determination of fluorine, chlorine and bromine in coal. Within this dissertation statistical methods were applied for the plan and for conducting experiments, and techniques for processing and analysis of results. Applying fractional factorial design, the influence of six variables on coal combustion in oxygen bomb and absorption of gaseous compounds during combustion was investigated. The analyzed variables were oxygen pressure, catalysts, combustion aid, type of absorbent solution, reducing agent and bomb cooling time. The concentration of ions in the absorption solution was measured by ion-selective electrode (the fluoride-ion) and by ion chromatography. The results of fractional factorial design were analyzed using Pareto-graphics, graphics of main effects and interaction plots. It was found that with the addition of the catalyst and with the increase of pH value of the absorption solution the concentration of halide ions in the absorption solution decreases. On the other hand, increase of oxygen pressure and the addition of combustion aid, increases the separation of halogens from the coal during combustion in an oxygen atmosphere. On the basis of preliminary studies, oxygen pressure and combustion aid were examined in more detail by using response surface methodology. Results of the optimization experiments were discussed using response surface plots, estimateted regression coefficients and analysis of variance. Since the optimum conditions for the determination of fluorine and chlorine differed, the group parameter - total halogens in coal (TCX) was defined. Total halogen in coal are expressed in terms of chlorine and it was chosen because it is the dominant halogen element in coal. The optimal parameters for the determination of halogens in coal were 0.5 g of coal samples, oxygen pressure of 2.5 MPa, 5 cm3 of H2O as the absorption solution, 5 cm3 of H2O2 as reducing reagent, 150 µL of mineral oil as the combustion aid, and a cooling interval of 15 minutes after combustion. Validation of proposed method was performed by determination of fluorine and chlorine in in-house prepared reference coal samples and in certified reference materials (BCR 460 and NIST 1632c). The relative standard deviation of determination of fluorine was less than 5.0%, and recovery was greater than 95%. The relative standard deviation of determination of chlorine was less than 6.0%, and recovery greater than 85%.The method was sensitive, with good reproducibility and accuracy. The proposed method was applied for determination of sulfur in coal. Validation of a method for determining the sulfur content is shown that the standard deviation of measurements was less than 6%, with a good reproducibility. The limit of detection (LOD) and limit of quantification (LOQ) is estimated for ion chromatography measurements and standard deviation of determining ions in the mixed standard solution of the lowest concentration. It has been found that the LOD and LOQ for fluorine were 0.4 mg / kg and 1.26 mg / kg; chlorine 0.84 mg / kg and 2.79 mg / kg; sulfur 2.2·10-5 % and 7.2·10-5 %. The proposed method was applied for the determination of fluorine, chlorine and sulfur in Kolubara and Kostolac coal samples

Ispitivanje adsorpcije fenola na makroporoznim polimernim adsorbensima

This work reports results on phenol adsorption from aqueous solution by porous copolymers based on glycidyl methacrylate: two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), were synthetized by suspension copolymerisation with ethylene glycol dimethacrylate. In addition, the two copolymer samples were functionalized with ethylene diamine. The amounts of adsorbed phenol were presented in the form of adsorptions isotherms, which were interpreted using Langmuir, Freundlich and Sips' equations. The first was found to express high level of agreement with experimental data. Phenol adsorption indicate the homogeneous distribution of active sites present on the investigated polymers. It was found that adsorption of phenol on copolymers is fast and depends on the presence of amino groups and on the pore size. From the obtained results, it was possible to distinguish macroporous polymer as a material which possesses the capacity for adsorption of phenol comparable to that of activated carbon.Ovaj rad se bavi proučavanjem adsorpcije fenola iz vodenih rastvora na kopolimerima različitih poroznih karakteristika i polarnosti. Korišćeni adsorbensi se baziraju na glicidil metakrilatu: dva uzorka makroporoznog poli(glicidil metakrilat-co-etilen glikol dimethakrilat) su sintetisani suspenzionom kopolimerizacijom sa etilen glikol dimetakrilatom. Dodatno, dva kopolimera su funkcionalizovani sa etilen diaminom. Količina adsorbovanog fenola je predstavljena u vidu adsorpcionih izotermi, koje su interpretirane korišćenjem Langmuir-ove, Freundlich-ove i Sips-ove jednačine: prva od ovih daje visok nivo slaganja sa eksperimentalnim podacima. Adsorpcija fenola ukazuje na homogenu raspodelu aktivnih mesta prisutnih u ispitivanim polimernim sistemima. Rezultati dobijeni u ovom istraživanju pokazuju da adsorpcija fenola na ispitivanim kopolimerima zavisi od prisustva amino grupa i od veličine pora. Adsorpcija fenola iz vodenih rastvora je brza u slučaju svih korišćenih adsorbenasa. Na osnovu dobivenih rezultata, može se zaključiti da su makroporozni polimeri materijali čije je adsorpcioni kapacitet za fenol uporediv sa onim koji ima aktivni ugalj

Ambient air particles: The use of ion chromatography and multivariate techniques in the analysis of water-soluble substances

Seventeen water-soluble substances (of sodium, ammonium, potassium, magnesium, calcium, formate, methanesulfonate, glyoxylate, chloride, nitrite, nitrate, glutarate, succinate, malate, malonate, sulfate and oxalate) in 94 samples of particle matter in the ambient air, collected over ten months, in a suburb of Belgrade (Serbia), were determined by ion chromatography. To apportion the sources of the air pollution, the log-transformed data were processed by applying multivariate techniques. Principal component and factor analysis identified three main factors controlling the data variability: stationary combustion processes with the highest loadings of oxalate, malonate and malate; landfill emission and secondary inorganic aerosol characterized by high levels of ammonium, nitrate and sulfate; a contribution of mineral dust composed of magnesium, calcium and chloride. The hierarchical cluster analysis pointed out a differentiation of the samples into five groups belonging to different variables inputs. For the classification of ambient air samples using nine selected ions, the recognition ability of linear discriminant analysis, k-nearest neighbors, and soft independent modeling of class analogy were 87.0, 94.6, and 97.8 %, respectively. Time-series analysis showed that the traffic emission is more pronounced in winter in contrast to the mineral dust influence, while the effect of waste combustion exhibits no trend

The Influence of Milk Type on the Proteolysis and Antioxidant Capacity of White-Brined Cheese Manufactured from High-Heat-Treated Milk Pretreated with Chymosin

We investigated the effect of milk type on the proteolysis and total antioxidant capacity (TEAC) of white-brined cheeses prepared from high-heat-treated (90 degrees C, 10 min) cow's and goat's milk, pretreated with chymosin at a low temperature (4 degrees C). The cheeses produced showed improved antioxidant characteristics and a high content of denatured whey proteins. However, these characteristics depend on the type of milk and the ripening time. Ripened cow's milk cheese had higher values of WSN/TN (water-soluble nitrogen per total nitrogen content) and TCA-SN/TN (nitrogen soluble in 12% trichloroacetic acid per total nitrogen), but similar PTA-SN/TN (nitrogen soluble in 5% phosphotungstic acid per total nitrogen) values were observed in ripened cheeses. The antioxidant potential of a WSF (water-soluble fraction) was higher in goat's milk cheese, but higher TEAC (total antioxidant capacity) values of WINF (water-insoluble fraction) were observed in matured cow's milk cheese. In vitro digestion slightly improved the radical scavenging capacity of WSF, whereas digested WINF had more than twice the capacity of their undigested counterparts. The cheeses prepared in this study could be a good source of antioxidant peptides. Further investigations of their in vitro and in vivo functionality need to be conducted

The development of methods for analysis of halogen elements in solid samples in oxygen atmosphere

Analiza kvaliteta ĉvrstih materijala, u zavisnosti od namene, obuhvata: tehniĉku analizu, elementarnu analizu, analizu makrokomponenata i mikrokomponenata. Poseban analitiĉki zadatak predstavlja analiza anjona u sloţenoj matrici ĉvrstog uzorka. U literaturi i analitiĉkoj praksi postoji veliki broj metoda za odreĊivanje halogenih elemenata, od klasiĉnih do savremenih (instrumentalnih), koje se razlikuju kako po principima rada, tako i po kriterijumima koji karakterišu analitiĉke tehnike, od kojih treba izdvojiti taĉnost i reproduktivnost. Predmet rada ove doktorske disertacije su halogeni elementi u uglju. Halogeni elementi u uglju su prisutni u niskim koncentracijama, ali je uticaj ovih elemenata na ţivotnu sredinu i zdravlje ljudi od posebnog znaĉaja. Istraţivanja u okviru ove disertacije obuhvataju analizu halogenih elemenata u uglju, rezultate istraţivanja pirohidrolitiĉke metode za odreĊivanje halogenih elemenata, kao i primenu eksperimentalnog dizajna za razvoj analitiĉkih metodologija. Cilj ove doktorske disertacije bio je da se utvrdi metodologija i odrede uslovi za istovremeno odreĊivanje fluora, hlora i broma u uglju. U okviru ove disertacije primenjene su statistiĉke metode za organizaciju i izvoĊenje eksperimenata, i tehnike za obradu i analizu dobijenih rezultata. Primenom frakcionisanog faktorijskog dizajna ispitan je uticaj šest promenljivih na sagorevanje uglja u kiseoniĉnoj bombi i apsorpciju gasovitih jedinjenja koja se tokom sagorevanja izdvajaju iz uglja. Ispitan je uticaj poĉetnog pritiska kiseonika, dodatak katalizatora i pomoćnog goriva na sagorevanje uglja, kao i tip apsorpcionog rastvora, dodatak redukcionog agensa i vreme hlaĊenja bombe nakon sagorevanja na apsorpciju gasovitih jedinjenja. Koncentracija jona u apsorpcionom rastvoru merena je potenciometrijski jon-selektivnom elektrodom (za fluorid-jon) i jonskom hromatografijom. Rezultati frakcionisanog faktorijskog dizajna su analizirani pomoću Pareto-grafika, grafika glavnih efekata i dijagrama interakcije parametara. UtvrĊeno je da se dodatkom katalizatora i povećanjem pH vrednosti apsorpcionog rastvora smanjuje koncentracija halogenid-jona u apsorpcionom rastvoru. S druge strane, povećanjem poĉetnog pritiska kiseonika i dodatkom pomoćnog goriva, povećava se izdvajanje halogenih elemenata iz uglja tokom sagorevanja u atmosferi kiseonika. Na osnovu rezultata preliminarnih istraţivanja, pritisak kiseonika i zapremina pomoćnog goriva su detaljnije ispitani primenom metodologije odgovora površine. Rezultati optimizacionih eksperimenata razmatrani su analizom grafika odgovora površine, procene regresionih koeficijenata i analize varijansi. Pošto su se optimalni uslovi za odreĊivanje fluora i hlora razlikovali, definisan je grupni parametar - ukupni halogeni u uglju (engl.- total halogen in coal, TCX). Ukupni halogeni u uglju su izraţeni preko hlora, a hlor je izabran iz razloga što predstavlja dominantan halogeni element u uglju. Optimalni uslovi metode odreĊivanja ukupnih halogena u uglju sagorevanjem u kiseoniĉnoj bombi su: pritisak kiseonika od 2,5 MPa, zapremina pomoćnog goriva od 150 µL, apsorpcioni rastvor je voda uz dodatak 0,5 % rastvora vodonik-peroksida i hlaĊenje kiseoniĉne bombe u ledenom kupatilu 15 minuta nakon sagorevanja uglja. Masa uzorka je bila 0,5 g. Validacija predloţene metode za odreĊivanje fluora i hlora sagorevanjem u kiseoniĉnoj bombi uraĊena je analizom internih referentnih uzoraka uglja i sertifikovanih referentnih ugljeva (BCR 460 i NIST 1632c). Relativna standardna devijacija odreĊivanja fluora bila je manja od 5,0 %, a procenat izdvojenog fluora u odnosu na referentnu vrednost veći od 95 %. Relativna standardna devijacija odreĊivanja hlora bila je manja od 6,0 %, a procenat izdvojenog hlora veći od 85 %, što znaĉi da je odreĊivanje fluora i hlora predloţenom metodom precizno i reproduktivno. Predloţenom metodom je odreĊen i sadrţaj sumpora u uglju. Validacija metode za odreĊivanje sumpora je pokazala da je standardna devijacija merenja manja od 6 %, uz dobru ponovljivost.Comprehensive analysis of the quality of solids, depending on the application, includes: technical analysis, elemental analysis, analysis of the macrocomponents and microcomponents. A special analytical task is the analysis of anions in a complex matrix of solid samples. In literature and in analytical practice there are a number of methods for the determination of halogens, from classic to contemporary (instrumental), which differ according to the principles of work, and according to criteria that characterize the analytical techniques of which accuracy and reproducibility should be allocated. The subject of the work of this doctoral thesis are halogen elements in coal. Halogen elements in coal are present in low concentrations, but the impact of these elements on the environment and human health is of particular importance. Research in this thesis are designed in the field of analysis of the halogen elements in coal, the results of pyrohydrolityc methods for the determination of halogens, as well as on the application of experimental design for the development of analytical methodologies. The aim of this doctoral thesis was to establish methodology and determine the conditions for simultaneous determination of fluorine, chlorine and bromine in coal. Within this dissertation statistical methods were applied for the plan and for conducting experiments, and techniques for processing and analysis of results. Applying fractional factorial design, the influence of six variables on coal combustion in oxygen bomb and absorption of gaseous compounds during combustion was investigated. The analyzed variables were oxygen pressure, catalysts, combustion aid, type of absorbent solution, reducing agent and bomb cooling time. The concentration of ions in the absorption solution was measured by ion-selective electrode (the fluoride-ion) and by ion chromatography. The results of fractional factorial design were analyzed using Pareto-graphics, graphics of main effects and interaction plots. It was found that with the addition of the catalyst and with the increase of pH value of the absorption solution the concentration of halide ions in the absorption solution decreases. On the other hand, increase of oxygen pressure and the addition of combustion aid, increases the separation of halogens from the coal during combustion in an oxygen atmosphere. On the basis of preliminary studies, oxygen pressure and combustion aid were examined in more detail by using response surface methodology. Results of the optimization experiments were discussed using response surface plots, estimateted regression coefficients and analysis of variance. Since the optimum conditions for the determination of fluorine and chlorine differed, the group parameter - total halogens in coal (TCX) was defined. Total halogen in coal are expressed in terms of chlorine and it was chosen because it is the dominant halogen element in coal. The optimal parameters for the determination of halogens in coal were 0.5 g of coal samples, oxygen pressure of 2.5 MPa, 5 cm3 of H2O as the absorption solution, 5 cm3 of H2O2 as reducing reagent, 150 µL of mineral oil as the combustion aid, and a cooling interval of 15 minutes after combustion. Validation of proposed method was performed by determination of fluorine and chlorine in in-house prepared reference coal samples and in certified reference materials (BCR 460 and NIST 1632c). The relative standard deviation of determination of fluorine was less than 5.0%, and recovery was greater than 95%. The relative standard deviation of determination of chlorine was less than 6.0%, and recovery greater than 85%.The method was sensitive, with good reproducibility and accuracy. The proposed method was applied for determination of sulfur in coal. Validation of a method for determining the sulfur content is shown that the standard deviation of measurements was less than 6%, with a good reproducibility. The limit of detection (LOD) and limit of quantification (LOQ) is estimated for ion chromatography measurements and standard deviation of determining ions in the mixed standard solution of the lowest concentration. It has been found that the LOD and LOQ for fluorine were 0.4 mg / kg and 1.26 mg / kg; chlorine 0.84 mg / kg and 2.79 mg / kg; sulfur 2.2·10-5 % and 7.2·10-5 %. The proposed method was applied for the determination of fluorine, chlorine and sulfur in Kolubara and Kostolac coal samples

Surface functional groups and degree of carbonization of selected chars from different processes and feedstock

The knowledge of the structural and chemical properties of biochars is decisive for their application as technical products. For this reason, methods for the characterization of biochars that are generally applicable and allow quality control are highly desired. Several methods that have shown potential in other studies were used to investigate two activated carbons and seven biochars from different processes and feedstock. The chars were chosen to cover a wide range of chemical composition and structuralproperties as a hardness test for the analytical methods used in this study. Specific problems connected with the pretreatment of samples and drawbacks of somemethods for some types of chars could be identified in an integrated consideration of the results from different methods. None of the spectroscopic methods was found to besuitable for the quality control of all types of chars. The most valuable results were obtained by chemical analysis that, however, required the complete determination ofthe main elements, including that of oxygen, and of inorganic components for adequate results. The combination of X-ray photoelectron spectroscopy (XPS) and FT-IRspectroscopy allows a rough characterization of surface functional groups, but cannot discriminate aliphatic and aromatic OH groups. FT-IR might be a suitable method forthe quality control of biochars made at lower temperature. The results of Raman spectroscopy did not well correlate with the amount of sp2 hybridized carbondetermined by XPS. A better correlation of XPS data was found with the electrical polarization determined by the method of spectral induced polarization that was usedfor the first time in conjunction with extensive analytical characterization

Aqueous extraction of anions from coal and fly ash followed by ion-chromatographic determination

Three different techniques were applied for the aqueous extraction of anions from coal and fly ash: rotary mixer- and ultrasonic-assisted extraction with different duration time, and microwave-assisted extraction at different temperatures. Validation showed that the ion-chromatographic method was suitable for the analysis of anions in coal and fly ash extracts. The variations in the amounts of anions using different extraction times during rotary-assisted extraction were minimal for all investigated anions. The efficiency of ultrasound-assisted extraction of anions from coal depended on the sonication time and was highest at 30 min. The ultrasound-assisted extraction was less efficient for the extraction of anions from fly ash than rotary-assisted extraction. Increase of temperature in the microwave-assisted extraction had a positive effect on the amounts of all anions extracted from coal and sulphate from fly ash, while the amounts of fluoride and chloride in fly ash extracts decreased. The microwave-assisted extraction of coal at 150°C was compared with standard ASTM methods, and results were in good agreement only for chloride. Changes in the pH value and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of coal particles in contact with water and different processes that occur under environmental conditions. [Projekat Ministarstva nauke Republike Srbije, br. 172030, br. 176006 i br. III43009