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

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 degrees 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

Određivanje teških metala u zemljištu i biomasi primenom potenciometrijske striping analize

In this paper the determination of lead, cadmium and zinc in soil and biomass was performed using potentiometric stripping analysis (PSA). In order to establish the optimal experimental conditions for PSA of Pb, Cd and Zn, the influence of pH value, time of metals extraction, stirring rate of the solution and the thickness of the mercury layer, as the working electrode, was investigated. The influence of mentioned parameters was tested for individual and simultaneous metals determination. The achieved limits of determination of single ions were for: lead 22.5 μg dm-3, cadmium 16.2 μg dm-3 and zinc 18.8 μg dm-3. The obtained results deviated from the expected for 1.1%, 1.9% and 1.8%, for lead, cadmium and zinc, respectively. For simultaneous determination, the method is tested using the ions contents as follows: 45.0 μg dm-3 for lead, 32.5 μg dm-3 for cadmium and 37.5 μg dm-3 for zinc. The relative errors for simultaneous determination were: 4.6% for lead, 1.9% for cadmium and 1.9% for zinc. For the established optimal conditions, except for lead, deviations did not exceed ±2%. It is shown that potentiometric stripping analysis is usable for individual and simultaneous determination of lead, cadmium and zinc in soil and biomass.U ovom radu je opisana primena potenciometrijske striping analize (PSA) za određivanje olova, kadmijuma i cinka u uzorcima zemljišta i biomase. U cilju utvrđivanja optimalnih eksperimentalnih uslova ispitivan je uticaj pH vrednosti rastvora, vremena izdvajanja metala iz rastvora, brzine mešanja rastvora i debljine filma žive, kao radne elektrode. Uticaj ovih parametara je ispitan za pojedinačno i istovremeno određivanje analiziranih metala. Postignute granice kvantifikacije pojedinačnih određivanja su za: olovo 22.5 μg dm-3, kadmijum 16.2 μg dm-3 i cink 18.8 μg dm-3. Dobiveni rezultati odstupaju od očekivanih vrednosti 1.1%, 1.9% i 1.8%, za olovo, kadmijum i cink, respektivno. Pri istovremenom određivanju sva tri ispitivana jona, metoda je testirana pri sledećim koncentracijama: 45.0 μg dm-3 za olovo, 32.5 μg dm-3 za kadmijum i 37.5 μg dm-3 za cink. Relativne greške simultanog određivanja su bile: 4.6% za olovo, 1.9% za kadmijum i 1.9% za cink. Obzirom da greške određivanja ne prelaze ±2%, osim za olovo, dobijeni rezultati ukazuju da se PSA može primeniti i za istovremeno određivanje sadržaja olova, kadmijuma i cinka u zemljištu i biomasi

Seasonal variations of concentrations of inorganic anions in atmospheric aerosols

8. Simpozijum "Hemija i zaštita životne sredine" sa međunarodnim učešćem : Knjiga izvoda ; 30. maj - 1. jun 2018; Kruševac, Srbija8th Symposium Chemistry and Environmental Protection with international participation : Book of Abstracts ; 30th May - 1st June 2018 ; Kruševac, Serbi

Comparison of sequential and single extraction in order to estimate the environmental impact of metals from fly ash

The aim of this paper is to simulate leaching of metals from fly ash in different environmental conditions using ultrasound and microwave-assisted extraction techniques. Single-agent extraction and sequential extraction procedures were used to determine the levels of different metals leaching. The concentration of metals (Al, Fe, Mn, Cd, Co, Cr, Ni, Pb, Cu, As and Be) in fly ash extracts were measured by inductively coupled plasma-atomic emission spectrometry. Single-agent extractions of metals were conducted at sonication times of 10, 20, 30, 40 and 50 min. Single-agent extraction with deionized water was also performed by exposing samples to microwave radiation at temperature of 50 degrees C. The sequential extraction was conducted according to the BCR procedure which was modified and applied to study the partitioning of metals in coal fly ash. The microwave-assisted sequential extraction was performed at different extraction temperatures: 50, 100 and 150 degrees C. The partitioning of metals between the individual fractions was investigated and discussed. The efficiency of the extraction process for each step was examined. In addition, the results of the microwave-assisted sequential extraction are compared to the results obtained by standard ASTM method. The mobility of most elements contained in the fly ash is markedly pH sensitive

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

MINERAL COMPOSITION OF TWO PEPPER CULTIVARS (CAPSICUM ANNUUM L) FROM SERBIA AT THREE RIPENING STAGES

The aim of this study was to evaluate mineral composition of two commonly cultivated pepper varieties from Serbia (cultivars Kalifornijska and Slonovo uvo), at three ripening stages. Concentration of macro (K, Ca, Mg, Na) and micro elements (Zn, Fe, Mn, Cu, B, Cr, Mo, Se, Li, Al), and heavy metals (Pb, Hg, Cd, As, Ni) was determined, using AAS and ICP-MS, after microwave-assisted digestion. Relative standard deviations of AAS and ICP-MS measurements, for the most of analyzed elements, were between 0.08 - 9.28 %, indicating that precision was satisfactory. Potassium was the most abundant element in all samples, followed by Mg and Ca. Among the investigated micro elements the average content of zinc was the highest, followed by iron, for most of analyzed samples. Zinc and iron were followed by copper, manganese and boron. Semi-mature peppers of cultivar Kalifornijska were richer in K, Ca, Mg, Fe and Zn compared to other maturity stages. For cultivar Slonovo uvo results were different compared to cultivar Kalifornijska. The content of K and Ni increased with ripening of fruit, while the content of magnesium decreased with ripening of fruit, which was not case for cultivar Kalifornijska. The higher values of Mg, Fe, Zn; lower values of Ca and higher values of Cu in cultivar Slonovo uvo were reported by different authors for other pepper varieties

Određivanje katjona i metala u pivu i sirovinama za proizvodnju piva metodama jonske hromatografije (IC) i atomske apsorpcione spektrofotometrije (AAS)

In order to control the quality of beer and raw materials for beer production, methods as ion chromatography (IC) and atomic absorption spectrophotometry (AAS) were applied. Water was analyzed as a raw material for beer production (urban, technological and demineralized water). Measurements of pH values indicated the increased pH values in the sample of tehnological water, but it had no impact on wort hopping, since the tested samples of wort, young beer and final product had a pH value in the expected range. Analyzing the content of anions and cations in the examinated water samples, it is shown that the concentration of these examinated anions (Cl- , NO3-, SO42- and PO43-) and cations (NH4+, Na+, K+, Ca2+, Mg2+), as and microelements (Fe, Cu i Zn) are within the limits prescribed by the Regulations on hygienic safety of drinking water and the Regulations of quality and other requirements for beer. Investigating contents of anions in samples of wort and beer (young beer and final product) showed that the contents of SO42- and NO3- ions were within recommended limits and the concentration of Cl- ions was above 150 mg/dm3, which may have an impact on sensory characteristics of beer, while changes in the content of PO43- ions were insignificant. Since AAS method is a standard method for analyzing content of alkaline and alkaline earth metals, the results obtained by this method in beer samples are taken as a referent results and according to them an analyse was performed and results obtained by IC method were compared. Results of the determination of Na, Ca and Mg in examinated water samples have shown variations, but both methods have shown the increased content of Na in demineralized water. The contents of alkaline and alkaline earth metals in wort and beer (young beer and final product) have shown that the results obtained by these two methods were in agreement.U cilju kontrole kvaliteta piva i sirovina za proizvodnju piva u Beogradskoj industriji piva (BIP) primenjene su metode jonske hromatografije (IC) i atomske apsorpcione spektrofotometrije (AAS). Od sirovina za proizvodnju piva analizirana je voda (gradska, tehnološka i demineralizovana). Merenja pH vrednosti ukazala su na povećanu pH vrednost u uzorku tehnološke vode, ali to nije imalo uticaj na ukomljavanje slada pošto su ispitivani uzorci sladovine, kao i uzorci mladog piva i gotovog proizvoda imali pH vrednost u očekivanom opsegu. Analiza sadržaja anjona i katjona u ispitivanim uzorcima vode, pokazala je da je koncentracija ispitivanih anjona (Cl-, NO3 -, SO4 2- i PO4 3-) i katjona (NH4 +, Na+, K+, Ca2+, Mg2+), kao i mikroelemenata (Fe, Cu i Zn) u granicama propisanim Pravilnikom o higijenskoj ispravnosti vode za piće i Pravilnikom o kvalitetu i drugim zahtevima za pivo. Ispitivanje sadržaja anjona u uzorcima sladovine i piva (mladog i gotovog proizvoda) pokazalo je da je sadržaj SO4 2-- i NO3 --jona bio u preporučenim granicama, koncentracija Cl-- jona bila je iznad 150 mg/dm3, što može imati uticaj na senzorne karakteristike piva, dok je promena sadržaja PO4 3--jona bila neznatna. Pošto je AAS standardna metoda za analizu sadržaja alkalnih i zemnoalkalnih metala, rezultati dobijeni ovom metodom u uzorcima piva uzeti su kao referentni i prema njima je izvršena analiza i upoređivanje rezultata dobijenih metodom IC. Rezultati određivanja Na, Ca i Mg u ispitivanim uzorcima vode, pokazala su odstupanja, ali su obe metode ukazale na povećan sadržaj natrijuma u demineralizovanoj vodi. Sadržaj alkalnih i zemnoalkalnih metala u uzorcima sladovine i piva (mladog i gotovog proizvoda) ukazao je da su rezultati dobijeni ovim dvema metodama bili u saglasnosti

Investigation of different extraction procedures for the determination of major and trace elements in coal by ICP-AES and ion chromatography

This paper presents the extraction of major and trace elements from a coal sample, in deionized water, by using three different extraction techniques. Rotary mixing and ultrasonic extraction were examined for different extraction times, while the microwave-assisted extraction was performed at different temperatures. Metal concentrations (Na, K, Ca, Mg, Al, Fe, Mn, Be, Cd, Co, Cr, Hg, As, Ni, Se, Sb and Pb) in solution were determined employing inductively coupled plasma atomic emission spectrometry; whereas the results obtained for Na, K, Ca and Mg were compared employing ion chromatography. Comparing the rotary-and ultrasonic-assisted extractions, it was shown that the former technique was more efficient for the determination of Fe, Na and Pb, whereas the latter one proved more efficient for the determination of Co and Cr ions. Microwave-assisted extraction was shown to be the most efficient method for all the tested elements in coal. In addition, sequential extraction of the elements was realized using microwave digestion. The results of the sequential extraction experiments indicated associations of investigated elements with a mineral phase and organic matrix. Sequential extraction provided information on possible leaching of As, Cd, Co, Cr, Ni, Pb, Fe and Mn under environmental conditions

Effect of ultrasound and chemical pretreatments on L-ascorbic acid of dried bell pepper (Capsicum annuum) studied by factorial design

Drying is one of the methods for the preservation of fruits and vegetables [1]. Peppers are still dried in open sunlight, although this method has many shortcomings (long drying time, microbial contamination, depending on weather conditions, final product of poor color) [2]. Deterioration of numerous nutrients, which occurs during drying, can be prevented by applying various pre-treatments and/or different drying methods [2–4]. The aim of this study was to investigate effects of different pretreatments and drying methods on L-ascorbic acid (L-AA) content in dried bell pepper. Effect of following parameters were studied: applied additive (0.25% citric acid, 0.25% potassium metabisulfite or their mixture), temperature, time, pH value of pretreatment solution, ultrasound pretreatment, pepper slices size, pepper mass and drying method (hot air-drying and freeze-drying). For organization of experiments fractional factorial design was used. Results showed that only the drying method significantly affects the content of L-AA after a month of storage. Freeze-drying was a better method for L-AA preservation. The interaction between the drying method and the size of pepper slices was also meaningful, although this interaction wasn’t statistically significant. Better preservation of L-AA, for hot air-dried samples, was achieved with a slices size of 4×4 cm compared to smaller (2×2 cm) and larger ones (8×8 cm). In the case of freeze-dried samples, the slice size didn’t affect the preservation of L-AA. The medium slices of the pepper fruit provided better penetration of the additives, which resulted in a better protective effect on L-AA during the hot air-drying. On the other hand, smaller pieces (2×2 cm) led to higher losses, probably due to the higher leaching of L-AA. Larger slices (8×8 cm) proved to be the most unfavorable for the preservation of L-AA (maybe due to less diffusion of additive during pretreatment and its later weak effect during drying)