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Determination of equilibrium amount of copper adsorbed on egg shells from copper(II) chloride dihydrate (T=308 K) : diploma thesis
No full textU ovom je diplomskom radu ispitana adsorpcija bakrovih iona na ljuskama jaja u ovisnosti o različitim početnim koncentracijama otopina bakrovih iona (2,876 mmol dm-3, 5,415 mmol dm-3, 8,200 mmol dm-3, 11,091 mmol dm-3 te 14,524 mmol dm-3) pri stalnoj temperaturi od 308 K, brzini miješanja od 200 okr min-1, u trajanju od 7 dana na ljuskama jaja promjera d < 0,250 µm. Količina adsorbiranih bakrovih iona (qe) na ljuskama jaja raste s porastom početne koncentracije bakrovih iona te postiže najvišu vrijednost pri najvišoj odabranoj početnoj koncentraciji vodene otopine bakrovog(II) klorida dihidrata (qe = 2,828 mmol g-1). S porastom početne koncentracije bakrovih iona u otopini raste i učinkovitost adsorpcije te je za sve otopine dobivena vrijednost veća od 90 %. Najviša dobivena vrijednost učinkovitosti adsorpcije iznosi 97,354 % pri najvišoj odabranoj početnoj koncentraciji vodene otopine bakrovog(II) klorida dihidrata, c0 = 14,524 mmol dm-3. Iz dobivenih rezultata proizlazi da su ljuske jaja veoma dobar adsorbens za izdvajanje bakra kao teškog metala iz vodenih otopina.In this diploma thesis, the adsorption of copper ions on egg shells was studied depending on the different initial concentrations of copper ion solutions (2.876 mmol dm-3, 5.415 mmol dm-3, 8.200 mmol dm-3, 11.091 mmol dm-3 and 14.524 mmol dm-3) at a constant temperature of 308 K, a stirring speed of 200 rpm-1 for 7 days on egg shells particles size of d <0.250 µm. The amount of copper ions adsorbed (qe) on egg shells increases with the increase of initial concentration of copper ions and reaches the highest value at the highest selected initial concentration of aqueous copper(II) chloride dihydrate solution (qe = 2,828 mmol g-1). With the increase of the initial concentration of copper ions in the solution, the adsorption efficiency increases, and for all solutions a value greater than 90 % was obtained. The highest adsorption efficiency value obtained was 97.354 % at the highest selected initial concentration of aqueous copper(II) chloride dihydrate solution, c0 = 14.524 mmol dm-3. The results show that egg shells are a very good adsorbent for copper removal as a heavy metal from aqueous solutions. Keywords: egg shells, adsorption, copper, spectrophotometry, FTIR
The equilibrium of cobalt ions adsorption on humus Potgrond H (T=308 K) : bachelor thesis
No full textIspitana je adsorpcija kobaltovih iona iz otopina kobaltovog(II) nitrata heksahidrata, različitih početnih koncentracija (4,284 mmol dm -3 , 8,161 mmol dm -3 , 11,223 mmol dm -3 , 20,406 mmol dm -3 te 30,610 mmol dm -3 ) na prosijanom humusu u šaržnom reaktoru pri odabranim ravnotežnim uvjetima: temperatura od 308 K, brzina okretaja od 200 okr min -1 , trajanje od 48 h te veličini čestica < 500 μm. Na temelju dobivenih rezultata može se zaključiti kako se maksimalna količina adsorbiranih kobaltovih iona na humusu (q e ) postiže pri početnoj koncentraciji kobaltovog(II) nitrata heksahidrata od 30,610 mmol dm -3 te iznosi q e = 0,367 mmol g -1 , dok je najviša učinkovitost adsorpcije postignuta kod početne koncentracije otopine od 4,284 mmol dm -3 te iznosi 19,056 %. Daljnjim porastom početne koncentracije kobaltovih iona u otopini učinkovitost adsorpcije kobaltovih iona na humusu opada. Uzimajući u obzir izračunate vrijednosti za koeficijent korelacije R 2 , kao i slaganje modela odabranih izotermi s eksperimentalno dobivenim podatcima može se zaključiti kako se adsorpcija kobaltovih iona na humusu može opisati Langmuirovim adsorpcijskim modelom (R 2 = 0,961).The adsorption of cobalt ions from cobalt(II) nitrate hexahydrate solutions of different initial concentrations (4.284 mmol dm -3 , 8.161 mmol dm -3 , 11.223 mmol dm -3 , 20.406 mmol dm -3 , and 30.610 mmol dm -3 ) was studied on sieved humus in a batch reactor under selected equilibrium conditions: temperature of 308 K, a stirring speed of 200 rpm, duration of 48 h, and particle size < 500 μm. Based on the results obtained, it can be concluded that the maximum amount of cobalt ions adsorbed on humus (q e ) is reached at an initial concentration of cobalt(II) nitrate hexahydrate of 30.610 mmol dm -3 with the value of q e = 0.367 mmol g -1 , while the highest adsorption efficiency was achieved at an initial solution concentration of 4.284 mmol dm -3 and was 19.056 %. Further increase in the initial concentration of cobalt ions in solution, decreases adsorption efficiency of cobalt ions on humus. Considering the calculated values for the correlation coefficient R 2 , as well as the fitting of the models of selected isotherms with the experimentally obtained data, it can be concluded that the adsorption of cobalt ions on humus can be described by the Langmuir adsorption model (R 2 = 0.961)
Corrosion inhibition of some metals by Padina pavonica (Linnaeus) Thivy extract : bachelor thesis
No full textZbog široke primjene konstrukcijskih materijala neminovno je djelovanje različitih vanjskih utjecaja koja uzrokuju oštećenja. Najznačajni proces odgovoran za ista je korozija pa se, kako bi se spriječila, podliježe metodama zaštite, prvenstveno upotrebom inhibitora. Zeleni inhibitori dobivaju sve više pozornosti jer većina dobivena iz prirodnih proizvoda djeluje antikorozivno, a ujedno su ekološki prihvatljivi i bezopasni te djeluju već pri niskim koncentracijama. Biljni ekstrakti smatraju se bogatim, prirodno sintetiziranim kemijskim spojevima. U ovom završnom radu ispitano je djelovanje vodenog ekstrakta smeđe alge Padina pavonica, u volumnim koncentracijama 0,2 % te 0,8 %, na inhibiciju korozije bakra, AISI 304 nehrđajućeg čelika te aluminija tehničke čistoće u 0,5 mol dm –3 otopini NaCl. Izvršena je ekstrakcija fenolnih spojeva u ultrazvučnoj kupelji te je sadržaj ukupnih fenola određen spektrofotometrijski. Daljnja su ispitivanja provedena elektrokemijskim metodama (metodom mjerenja potencijala otvorenog kruga, metodom linearne polarizacije i potenciodinamičkom polarizacijskom metodom), dok je površina ispitivanih materijala analizirana optičkim mikroskopom pri različitim uvećanjima. Na temelju dobivenih rezultata elektrokemijskih mjerenja, moguće je vodeni ekstrakt P. pavonica klasificirati kao djelotvorni inhibitor korozije u vodenoj otopini soli za sve ispitane metale, a prvenstveno za aluminij. Djelotvornost inhibicije raste s porastom koncentracije ekstrakta u otopini pa se tako 0,8 %-tni ekstarakt pokazao kao najbolji inhibitor korozijskog djelovanja.Wide usage of construction materials in modern world means that such materials are exposed to various external influences that result in damage of the material. Most important process responsible for such damage is corrosion. As a mean to prevent those damages, materials are introduced to methods of protection, most often by using inhibitors. Green inhibitors are attracting more and more attention since majority of them are anti-corrosive and are produced from natural sources, while at the same time are ecologically sustainable and harmless and are effective even in small concentrations. Herbal extracts are considered to be rich with naturally synthesized chemical compounds. This bachelor thesis aims to study the inhibition effect of aquaeous extract of brown algae Padina pavonica (in 0.2% and 0.8% (v/v) concentration) on corrosion of copper, AISI 304 stainless steel and technical aluminium in the 0.5 mol dm –3 NaCl solution. Total phenolic compounds were isolated by ultrasound assisted extraction and were determined spectrofotometrically. Following experiments were conducted using electrochemical techniques (linear polarization and potentiodynamic polarization technique). Surface of the samples was analyzed using optical microscope with various enlargements. The collected experimental results revealed that aqueous extract of P. pavonica can be classified as an effective corrosion inhibitor in saline solution for all of the tested metals, especially for aluminium. The inhibition efficiency increased with increasing extract concentration, thus 0.8% extract proved to be the best corrosion inhibitor
CORROSION BEHAVIOR OF CuAlMnZn ALLOY IN NaCl SOLUTION : diploma thesis
No full textU radu je provedeno ispitivanje elektrokemijskog ponašanja CuAlMnZn legure u 0.5 mol dm -3 NaCl otopini različitih koncentracija (0,1, 0,5, 0,9 i 1,5 %) pri T = 20 o C i pH = 7.4, uz miješanje magnetskom miješalicom s brzinom vrtnje miješala od 150 o/min. Primijenjene su elektrokemijske tehnike kao što su mjerenje potencijala otvorenog strujnog kruga, metode linearne i potenciodinamičke polarizacije. Također je provedeno i mjerenje metodom cikličke voltametrije, u području potencijala od -1.2 V do +1.2 V s brzinom promjene potencijala od 10 mVs -1 . Povećanje koncentracije kloridih iona dovodi do negativiranja potencijala otvorenog strujnog kruga legure, povećanja gustoće korozijske struje i smanjenja vrijednosti polarizacijskog otpora. Korodirane površine elektroda nakon polarizacijskih mjerenja, ispitane su optičkim mikroskopom.The electrochemical behavior of CuAlMnZn alloy in NaCl solution of different concentrations (0,1, 0,5, 0,9 and 1,5 %) at T = 20 o C and pH = 7.4, stirred with a magnetic stirrer with a stirrer speed of 150 rpm, was examined. Electrochemical techniques such as open circuit potential measurement, linear and potentiodynamic polarization methods have been applied. Measurements were also performed by the cyclic voltammetry method, in the potential range from -1.2 V to +1.2 V with a potential scan rate of 10 mVs -1 . Increase in concentration of chloride ions leads to a lowering open circuit potential values of alloy, increase in corrosion current density and a decrease in values of the polarization resistance. After polarization measurements, corroded electrode surfaces, were examined with an optical microscope
Production of fruit spirits and liqueurs : bachelor thesis
No full textVoćne rakije su jedno od najraširenijih alkoholnih pića. Mogu se proizvesti od raznog voća, a tehnološki procesi koji ukljuĉuju postupak proizvodnje voćnih rakija su priprema sirovine, fermentacija i destilacija. Likeri su takoĊer jaka alkoholna pića koja se ovisno o tehnološkom postupku i vrsti sirovine dijele u više skupina, od kojih su jedna voćni likeri. Za proizvodnju likera je potreban voćni destilat u koji se potapa voće (maceracija) kako bi se liker aromatizirao. Cilj ovog rada bio je detaljno opisati sve jediniĉne procese tokom postupka proizvodnje voćnih likera, navesti potencijalne probleme koji se mogu javiti kao i moguća rješenja istih. Kako bi proizvod bio pogodan za tržište moraju se ispoštovati propisane zakonske norme, pa je rad popraćen i odreĊenim pravilnicima.Fruit spirits are one of the most widespread strong alcoholic drinks. They can be produced from various fruits, and the technological processes are preparation of raw materials, fermentation and distillation. Liqueurs are also strong alcoholic drinks that can be divided into several groups depending on the technological production process and the type of raw materials. One of them are fruit liqueurs that can be produced from different types of fruit. For the production of fruit liqueurs, fruits are macerated in fruit distillate in order to get the final liqueur aroma. The aim of this work was to describe in detail unit operations in the fruit liqueur production, to list potential problems that may arise and their possible solutions. In order to make product suitable for the market, the prescribed norms for that type of product must be respected, so the work is accompanied by certain laws and regulations
Electric potential and electric double layer theories : bachelor thesis
No full textU ovom teorijskom radu razmatrani su fizikalni procesi koji su odgovorni za nastajanje električnog potencijala na dodirnim površinama faza, njegovom mijenjanju i profilu udaljenosti od krutih elektroda (čestica). Nadalje, analogijom sa gravitacijom objašnjeni su pojmovi električnog potencijala i električnog polja na jednostavan i lako shvatljiv način. Na osnovu ovog razmatranja, reakcije prijenosa elektrona između dodirne površine elektroda/elektrolit su razmatrane u kontekstu proboja električnog kondenzatora. Razmatrane su fizikalne pojave koje utječu na profil pada potencijala elektrode kroz otopine iona na temelju Poissonove jednadžbe (Gaussovog zakona). Na osnovu tih pojava, izložen je kritički osvrt na postojeće modele električnog dvosloja. Analiziran je sam pojam dvosloj, njegova literaturna uporaba i terminološki problemi njegove uporabe u kontekstu same njegove građe. Utjecaj koncentracije iona, vrste otapala, električnog potencijala na vrijednosti kapaciteta dvosloja, kao i objašnjenje porijekla i reda veličine dvosloja kao i njegovih kapaciteta su analizirani i razjašnjeni. Razlike strukture dvosloja za mikro i nanoelektrode su analizirani i razjašnjeni. Na kraju je napravljen osvrt na modeliranje dvosloja preko ekvivalentnih strujnih krugova.In this theoretical paper, physical processes responsible for formation of electrical potential on the contact surfaces of the phases, its changing and profile dependent on the distance from the solid electrodes (particles) have been discussed. Further, analogously with gravitation, terms of electrical potential and electrical field have been explained in an easy and understandable way. Based on this reflection, reactions of electron transfer in between contact surface electrode/electrolyte have been examined in the context of breakdown of electric capacitor. Physical occurrences that effect the profile of drop in electrode potential through ionic solution based on Poisson’s equation (Gauss’s law) have been discussed. Based on these occurrences a critical review has been presented on existing electrical double layer models. Electrical double layer itself has been analysed, as well as its literary use and terminological problems of its use in the context of its structure itself. The influence of ion concentration, types of solvents, the electrical potential on the value of double layer capacity, as well as an explanation of double layer origin, order of magnitude and its capacity have been analysed and explained. The difference in double layer structure for micro and nanoelectrodes has also been analysed and explained. At the end, an overview of modelling the double layer has been made by using equivalent electrical circuits
Manufacturing solar cells based on nanocrystalic ZnO : master thesis
No full textU radu su pripravljene DSSC solarne ćelije na bazi nanokristaličnog cink(II) oksida te je kroz četrnaest dana mjeren fotoinducirani napon pod umjetnim osvjetljenjem. Pasta nanokristaličnog ZnO pripremljena je na dva načina, jedan s kiselinom, a drugi s alkoholom te se na taj način promatrao utjecaj tih otapala na kvalitetu poroznog sloja. U obje paste dodan je neionski dispergent Triton-X 100, koji služi kao sredstvo za kvašenje te pomaže dobivanju kompaktnog poroznog sloja koji dobro prijanja za površinu. Stakalca s nanesenim tankim slojem nanokristaličnog ZnO termički su obrađena te proučavana digitalnim mikroskopom. Također, radi usporedbe aktivnosti sintetskih i prirodnih bojila, korišteno je N3 sintetsko bojlo i antocijanin koji je prirodni pigment ekstrahiran u etanolu iz suhog cvijeta hibiskusa. Izmjereni su UV-Vis sprektri korištenih bojila. Rezultati ispitivanja pokazuju da sve ćelije pripravljene i s kiselinom i s alkoholom, pokazuju više vrijednosti fotoinduciranog napona primjenom antocijana kao bojila.In this paper, DSSC solar cells based on nanocrystal zinc(II) oxide were manufactured and over the period of fourteen days, photoinduced voltage was mesured under the artificial light. Nanocrystal paste of ZnO was made in two ways, first using acid and second using alcohol which made it possible to see the effect of the used solution on the quality on the layer. Both pastes were made with the addition of nonionic dispersion of Triton-X 100 that is used as wetting agent and helps to get compact layer. Plates with nanocrystal layer of ZnO were analysed with digital microscope after thermic processing. For comparison of the dye activity two dyes were used, synthetic N3 and anthocyanin which is a natural pigment and was extracted into ethanol from dry hibiscus flower. UV-Vis spectra of the used dyes were determined. Results show that all cells made with alcohol and with acid show higher values of photoinduced voltage using anthocyanin as a dy
Influence of AlOOH, Al2O3 and beta-FeOOH nanoparticles on the response of ion-selective membranes to iron(III) cations : master thesis
No full textU ovom diplomskom radu opisano je ispitivanje membrana za ionsko-selektivne elektrode (ISE) koje su prethodno napravljene od mješavine željezovog fosfata, srebrovog sulfida, te politetrafluoroetilena. Membrane su obogaćene nanočesticama metalnih oksida, a služe za potenciometrijsko određivanje željezovih(III) kationa u otopini acetatnog pufera pH=5,00 metodom slijednog razrjeđenja. Osnovni cilj ovog diplomskog rada je usporediti odziv membrana koje sadrže nanočestice akaganeita s membranama koje sadrže nanočestice aluminijevog oksida i aluminijevog hidroksida. Metoda korištena u ovom radu naziva se potenciometrijska metoda, koja se pokazala najučinkovitijom zbog svoje jednostavnosti, praktičnosti, te niske cijene. Rezultati ispitivanja prikazani su grafički.This thesis describes the testing of membranes for ion-selective electrodes (ISE), which were previously made of a mixture of iron phosphate, silver sulfide, and polytetrafluoroethylene. The membranes were enriched with metal oxide nanoparticles and they are used for potentiometric determination of iron(III) cations in acetate buffer solution pH = 5.00 by sequential dilution. The main goal of this thesis is to compare the response of membranes containing nanoparticles of akaganeite with membranes containing nanoparticles of aluminium oxide and aluminum hydroxide. The method used in this thesis was potentiometric method, which has been proven the most effective because of its simplicity, practicality, and low cost. The test results were presented graphically
Upute: Kako napisati diplomski / završni rad
No full textSvaki student koji počinje pisati završni ili diplomski rad rješava svoje nedoumice vezane za način pisanja, a posebna se pažnja posvećuje obradi literature i načinu pisanja iste. Cilj radionice je dodatno obrazovati studente i pripremiti ih za uspješnije savladavanje procesa oblikovanja i izrade diplomskog / završnog rada. Studentima će se pojasniti proces akademskog pisanja te sam proces izrade rada s naglaskom na područje kemije i kemijskog inženjerstva, prehrambene tehnologije i farmacije. Tijekom radionice pružit će se znanja vezana uz prikupljanje i analizu znanstvene i stručne relevantne literature, načine obrade i prezentacije prikupljenih podatak
Determination of hydrated cement composites properties with addition of waste container glass using thermal analysis (TG/DTG) : diploma thesis
No full textU ovom radu provedeno je određivanje svojstava hidratiziranih cementnih kompozita u vodocementnom omjeru (V/C) 0,5 bez dodatka i uz dodatak otpadnog ambalažnog stakla u masenom udjelu od 30%. Ukupno je analizirano 6 uzoraka. Dva uzoraka su sadržavala čisti portland cement (CEM I 42,5R.), te su hidratizirani 7 i 90 dana pri temperaturi od 20 °C. Od preostala četiri uzorka, dva su sadržavala čestice stakla veličine do 45 µm, a dva čestice stakla veličine između 125 i 250 µm. Ti uzorci su također hidratizirani 7 i 90 dana. Nakon hidratizacije provedena je termogravimetrijska analiza. Iz dobivenih rezultata vidljivo je da se dodatkom otpadnog stakla veličine čestica manjih od 45 µm u portland cementnim uzorcima događa pucolanska reakcija između portlandita i reaktivnog SiO 2 iz stakla. Pucolanska reakcija se također događa i u slučaju dodataka čestica stakla veličine između 125 i 250 µm ali u manjoj mjeri. Brzina i početak pucolanske reakcije ovisi o veličini čestica stakla. Dodatkom otpadnog ambalažnog stakla smanjuje se stupanj hidratacije cementa, što je posebno izraženo kod krupnijih frakcija.Properties of hydrated cemet composites, in water – cement ratio (W/C) of 0.5, were determined in this paper. Properties were tested with and without addition of waste contenier glass to the cement composites. The content of added glass was 30% of cement weight. There were 6 tested samples in total. Two of those samples had pure portland cement (CEM I 42,5 R) and they were hydrated for 7 and 90 days at 20 °C. From four remaining samples, two of them had contained waste container glass particles smaller than 45 µm and two of them contained waste container glass with particles between sizes 125-250 µm. Those samples were also hydreted 7 and 90 days at 20 °C. After hydratation, thermogravimetric analysis was conducted. From the obtained data, it can be seen that adding waste container glass particles smaller than 45 µm to portland cement samples triggers the pozzolanic reaction between portlantides and reactive SiO2 from the glass. Moreover, the reaction occurs in a situation when the glass particles, ranging from 125 µm to 250 µm,are added into the cement, only in smaller quantities. The beginning and the rate at which the pozzolanic reaction occurs depends on the size of the glass particles. Furthermore, the addition of waste container glass decreases the level of hydration of the cement, which is highly prominent in large fractions