Synthesis, characterization and sorption properties of bentonite modified by tetraalkylammonium ions

Ovaj rad je posvećen sintezi organobentonita (OB) dobijenih modifikacijom kvaternernim alkilamonijum katjonima (KAAK), karakterizaciji dobijenih uzoraka, ispitivanju njihovih adsorpcionih svojstava prema organskim i neorganskim zagađivačima prisutnim u otpadnim vodama tekstilne industrije, kao i utvrđivanju multifunkcionalnog adsorbensa koji bi usled posedovanja i hidrofilne i organofilne površine uspešno mogao biti upotrebljen prilikom tretmana otpadnih voda kompleksnog sastava Sintetisani OB dobijeni su od bentonitne gline sa lokaliteta Bogovina (Srbija). Polazni uzorak frakcije <74 μm je najpre Na–izmenjen (Na–B), a zatim modifikovan KAAK jonima. Modifikacijom su dobijene dve serije organobentonita. U prvoj seriji je korišćen heksadeciltrimetilamonijum (HDTMA) bromid, pri čemu količina odgovara vrednostima Kizm=0,2–3,0 (gde je Kizm broj koji pokazuje odnos KAAK jona prema vrednosti kapaicteta katjonske izmene). Druga sereija je dobijena modifikacijom bentonita KAAK različite dužine alkil niza: HDTMA bromidom, dodeciltrimetilamonijum (DDTMA) bromidom i tetrametilamonijum (TMA) bromidom, pri čemu je Kizm=2,0. Dobijeni uzorci su označeni kao 0,2 HDTMA–B, 0,5 HDTMA–B, 1,0 HDTMA–B, 2,0 HDTMA–B, 3,0 HDTMA–B, 2,0 DDTMA–B, 2,0 TMA–B. Ispitivan je uticaj modifikacije na strukturu, teksturalna i adsorpciona svojstva bentonita. Hemijski sastav polaznog bentonita i Na–B je određen standardnom silikatnom analizom, dok je procena udela organske faze kod OB izvršena žarenjem uzoraka na 800°C, čime je potvrđeno prisustvo organske faze čiji udeo raste sa porastom Kizm i sa porastom dužine alkil niza KAAK. Fazni sastav, teksturalna i morfološka svojstva Na–B i uzoraka OB određeni su korišćenjem XRD analize, IC analize, metodom fizisorpcije N2 i SEM mikroskopije. Utvrđeno je da primenjeni postupci modifikacije dovode isključivo do izmene katjona u međulamelarnom sloju smektita, dok modifikacija ne deluje na druge prateće minerale u bentonitu (kvarc, kalcit, feldspat). Kod uzoraka 0,2, 0,5 i 1,0 HDTMA–B na osnovu vrednosti d001 utvrđeno je da dolazi do formiranja monosloja, dvosloja i pseudo-tri molekulskog sloja HDTMA katjona, dok kod uzoraka sa Kizm=1,0-3,0 HDTMA–B unutar međusloja dolazi do formiranja organske faze za koju je pretpostavljeno da je delimično sastavljena od parafinskih slojeva. IC spektri uzoraka OB ukazuju na prisustvo tri nove trake koje potiču od vibracija metilenske grupe, što je još jedna potvrda ugradnje KAAK. Kod svih OB osim 2,0 TMA–B, utvrđeno je da sa povećanjem Kizm i dužine alkil niza KAAK dolazi do značajne promene teksturalnih svojstava u odnosu na polazni Na–B. Uočen je pad specifične površine materijla i prelazak mikro i mezoporoznog materijala u gotovo potpuno neporozan. Sa druge strane, 2,0 TMA–B i Na–B imaju slične teksturalne osobine, što je posledica ugradnje kratkolančanog katjona TMA u obliku „pilara“, a posledica je stvaranje mikroporoznog materijala. Analizom SEM mikrofotografija snimljenih uzoraka analizirane HDTMA serije uočava se da svi izorci zadržavaju slojevitu strukturu filosilikata...The synthesis of organo-bentonites (OB) obtained by modification with quaternary alkylammonium cations (QAAC), their characterization and evaluation of their efficiency as adsorbents for organic and inorganic aqueous pollutants was investigated in this work. Particular attention was dedicated to the removal of pollutants from textile industry effluents, and obtainment of a multifunctional adsorbent that incorporates both hydrophilic and hydrophobic surfaces, which can be successfully applied in the purification of wastewaters with complex composition. The synthesized OBs were obtained from smectite containing clay bentonite from Bogovina basin (Serbia). The starting material, consisted of particles with diameters of up to 74μm, was submitted to Na-exchange (Na-B), and subsequent modification with QAAC ions. Two series of OBs were obtained in this manner. The first series was obtained using hexadecyltrimethylammonium (HDTMA) bromide. The amount of introduced HDTMA was expressed as Kexch=0,2–3,0, where the value of Kexch represents the ratio between QAAC ions and the cation exchange capacity of the clay. The second series was obtained by the bentonite modification using QAACs (Kexch=2,0) with different alkyl chain lengths: HDTMA bromide, dodecyltrimethylammonium (DDTMA) bromide and tetramethylammonium (TMA) bromide. The samples were denoted as 0,2 HDTMA–B, 0,5 HDTMA–B, 1,0 HDTMA–B, 2,0 HDTMA–B i 3,0 HDTMA–B, 2,0 DDTMA–B, 2,0 TMA–B. The influence of the modification on the structural, textural and adsorption properties of bentonite was investigated. The chemical compositions of the starting and Na-exchanged bentonite were determined by standard silicate analysis, and the fraction of the organic phase in the samples was estimated after calcination at 800°C. The increasing presence of the organic phase with increased Kexch or QAAC alkyl chain length was confirmed. The phase composition, textural and morphological properties of the Na-B and OB samples were determined by XRD and IR analyses, N2 physisorption and SEM microscopy. It was found that the applied modification procedures resulted in the exclusive exchange of cations from the smectite interlamellar region, with no impact on the accompanying minerals present in bentonite (quartz, calcite, feldspar). In the case of 0,2, 0,5 i 1,0 HDTMA–B samples, it was concluded from the d001 values that the consequence of the modification was the formation of mono-, bi- or pseudotrimolecular HDTMA layers. As for the 1,0–3,0 HDTMA-B samples it is presumed that the formation of organic phase occurred within the interlamellar region, which is probably partially consisted of paraffin layers. The IR spectra of the OBs exhibited the occurrence of three new bands corresponding to methyl group vibrations, which is another proof of the incorporation of QAACs. For all OB samples, except for the 2,0 TMA–B, was established that the increase in the Kexch values and alkyl chain lengths lead to significant changes in the textural properties comparing to those of the starting Na-B material. The decrease in the specific surface was observed, and the starting micro/mesoporous material was turned almost completely nonporous. On the other hand, the 2,0 TMA–B and Na-B exhibited similar textural properties, which is a consequence of the incorporation of short-alkylchained TMA cations in the form of pillars resulting in a microporous material The analysis of the SEM micrographs of the HDTMA sample series it was observed that all the samples retained characteristic phylosilicate layered structure..

Kinetic and thermodynamic study of nicotine degradation by oxone® activated by cobalt based catalyst

Acid activated montmorillonite was impregnated with Co2+ ions, calcined at 450 , and used as catalyst for Oxone® activation in catalytic oxidative degradation of nicotine. Catalytic tests were performed in temperature range from 30 °C to 60 °C in order to obtain kinetic data. Kinetic study at different temperatures showed that catalytic degradation of nicotine corresponded to the first-order kinetic model. The activation energy of the investigated degradation process was determined by applying Arrhenius equation

Carbonized chitosan-bentonite as electrode material

Bentonite clay has shown to be a versatile material that can be easily modified and applied as an adsorbent, (electro)catalyst, or as a support for (electro)catalyst. The carbon-clay composites combine a relatively high specific surface area of the clay with a good electrical conductivity of carbon.In this paper, the effect of the applied carbonization procedure on the electrochemical properties of bentonite-carbon composite was investigated. Chitosan-modified bentonite was carbonized by conventional thermal degradation and by the hydrothermal procedure. The electrochemical characterization was performed by cyclic voltammetry and electrochemical impedance spectroscopy. The response to Fe(CN)63-/4- and Ru(NH3)62+/3+ redox probe showed that the thermally treated sample shows somewhat higher electrochemical activity and lower charge-transfer resistance. However, an investigation of composites activity toward minophenazone, performed in the pH range 3-9 showed that the hydrothermally obtained sample shows higher activity at pH above 5, while the thermally obtained sample was more active at pH below 5

Adsorption of nicotine from aqueous solutions on montmorillonite and acid – modified montmorillonite

Montmorillonite (Mt) and acid modified montmorillonite (MtA) were tested as nicotine adsorbents. The samples were characterized using FT-IR spectroscopy and low temperature nitrogen physisorption. Nicotine adsorption was performed with respect to contact time, pH and initial nicotine concentration. The kinetics of adsorption obeyed the pseudo-second-order kinetics. The optimal pH values for nicotine adsorption were 6 and 9 for Mt and MtA, respectively. The isotherms related to adsorption on Mt at pH = 6 and 9 as well as for MtA at pH=6 were best fitted with Sips isotherm model, while adsorption onto MtA at pH=9 obeyed Langmuir isotherm model.Монморијонит (Mt) и кисело модификован монморијонит (MtA) су испитани као адсорбенси никотина. Узорци су окарактерисани FT-IR спектроскопијом и нискотемпературном физисорпцијом азота. Адсорпција никотина испитивана је у зависности од времена контакта, pH и почетне концентрације никотина. Псеудодруги ред добро описује кинетику адсорпције. Оптимална pH вредност за адсорпцију никотина на Mt је 6 док је за MtA 9. Сипсов модел најбоље описује адсорпцију никотина на Mt на pH = 6 и 9 као и на MtA на pH = 6, док се aдсорпција на MtA на pH = 9 одвија по Лангмировом моделу

The Influence of pH on Electrochemical Behavior of Nicotine- Clay based Electrodes

Montmorillonite based clay was acid activated. Nicotine was adsorbed on untreated and acid activated clay from its aqueous solution at either pH=6 or pH=9.26 (unadjusted pH solution). The XRD analysis revealed that the 001 basal spacing of montmorillonite after nicotine adsorption was around 1.38 nm, regardless of clay treatment or pH of adsorption. The obtained values for basal spacing indicate that nicotine is in monolayer arrangement. In order to investigate electrochemical properties, untreated and acid activated clay, with and without nicotine, were used as modifier of carbon paste electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to study electrochemical response of clay-modified electrodes toward ferrocyanide probe. The nicotine-modified untreated clay used as paste electrode showed enhanced electrochemical response toward ferrocyanide probe in comparison to electrode based on clay without nicotine. On the other hand, adsorbed nicotine on acid activate clay resulted in lower electrode activity. Electrochemical response of adsorbed nicotine was studied at different pH. Nicotine oxidation at each of investigated samples followed the same trend regardless of clay treatment or pH at which adsorption was performed. For all samples, nicotine oxidation peak potential showed linear dependence on pH in pH range from 3.7 to 9.0, with slopes close to the value of 59 mVdec-1 expected for equal number of protons and electrons involved in the reaction. The nicotine reduction process was best resolved at pH = 1 at potential around -1.35 V, while the following cathodic wave observed at potential around -1.5 V was ascribed to the cathodic hydrogen reduction. Mechanism of electrochemical oxidation was not influenced by pH of adsorption, i.e., nicotine form. The amount of adsorbed nicotine was not correlated with the electrochemical activity suggesting that only small number of adsorbed nicotine was involved in electrochemical response.Глина са високим садржајем монморијонита је кисело активирана. Извршена је адсорпција никотина из воденог раствора на полазној и кисело- активираној глини на pH=6 или pH=9,26 (неподешен pH раствора). На основу резултата XRD анализе утврђено је да је након адсорпције никотина међураванско растојање 001 равни монморијонита 1,38 nm, без обзира на то да ли је глина активирана или не, као и на којој pH је адсорпција вршена. Добијене вредности за међураванско растојање указују да је никотин уграђен у облику монослоја. Полазна и кисело-активирана глина, са и без никотина коришћене су за модификацију карбон- паста електроде да би се испитала електрохемијска својства. Циклична волтаматрија и електрохемијска импедансна спектроскопија су коришћене да би се испитао електрохемијски одговор према фероцијанидној проби глином-модификованих електрода. Полазна никотином-модификована глина коришћена као паста-електрода показала је бољи електрохемијски одговор према фероцијанидној проби у односу на електроду на бази глине без никотина. Насупрот томе, никотин адсорбован на кисело- активираној глини довео је до смањења електродне активности. Електрохемијски одговор адсорбованог никотина испитиван је на различитим pH вредностима раствора. Оксидација никотина је код свих испитиваних узорка имала исти тренд, без обзира на киселу модификацију и/или pH вредност на којој је вршена адсорпција. Код свих узорака, потенцијал на којем се налази пик оксидације никотина показује линеарну зависност од pH у интервалу pH од 3,7 до 9,0, са нагибом приближно 59 mVdec-1 што одговара реакцији у којој је укључен једнак број протона и електрона. Процес редукције никотина најбоље се уочава на pH = 1 на потенцијалу око -1,35 V, док је катодни талас који следи на потенцијалу око -1,5 V приписан катодној редукцији водоника. На механизам електрохемијске оксидације нису утицали ни pH адсорпције, као ни форма никотина присутна на тој pH вредности. Количина адсорбованог никотина није утицала на електрохемијску активност указујући да је само мала количина адсорбованог никотина учествовала у електрохемијском одговору

Alkylammonium clay based nanocomposites vs. alkylammonium- modified lignocellulosic materials in adsorption of Congo Red

In this study, lignocellulose waste materials and smectite clay were modified into adsorbents with surface free ammonium groups. Poplar waste biomass and brewer’s spent grain were chemically modified. Smectite based adsorbents were obtained by intercalation of biopolymer chitosan and hexadecyl trimethylammonium (HDTMA+) cations in smectite structure. The samples were characterized by using X-ray diffraction, elemental analysis and FTIR spectroscopy. The adsorbents were tested for removal of azo dye Congo Red (CR). The concentration of CR was analyzed before and after adsorption test using Thermo Electron Nicolet Evolution 500 UV-VIS spectrophotometer in wavelength range from 250 – 800 nm. It was estimated that adsorption isotherms of CR for all investigated adsorbents showed best fit with Langmuir adsorption model

The influence of clay modification on electrochemical behavior of quinhydrone

Glina bogata monmorijonitom iz Vajominga je modifikovana kiselom aktivacijom i procesom pilarenja. Ovako izmenjena glina, kao i polazna glina, je naneta na površinu elektrode od staklatog ugljenika pomoću Nafiona. Aktivnost ovih elektroda je ispitana na primeru redoks para hinon/hidrohinon (Q/QH2) u puferovanom i nepuferovanm rastvoru. Način modifikacije glina je uticao na aktivnost elektroda i mehanizam redoks rekacijeMontmorillonite originated from Wyoming was modified by acid activation and aluminum pillaring process. The samples of clay obtained in this manner, as well as starting clay, were applied at the surface of a glassy carbon electrode by the means of Nafion. The activity of these electrodes was investigated on the redox couple quinone/hydroquinone (Q/QH2) in buffered and unbuffered solutions. The type of clay modification influenced the activity of the electrodes and the mechanism of the redox reaction

Catalytic oxidative degradation of Orange G dye: the effect of different reaction parameters

Catalytic oxidative degradation of a textile dye Orange G was investigated in the reaction system where oxidant Oxone® was used as a source of SO4˙ˉ anion radicals. Cobalt-doped alumina was tested as a heterogenous catalysts for Oxone® activation. The catalyst was synthetized and calcined at 500 °C. The influence of different reaction parameters was followed: the Oxone® dosage, Orange G concentration and initial pH of the reaction solution. The Oxone® dosage was varied from 10 mg to 80 mg. Small differences in degradation efficiency were observed but mass of 40 mg of Oxone® was found to be optimal in the first hour of the reaction. The effect of the Orange G concentration was investigated in the range from 20 mg dm-3 to 50mg dm-3. For the concentration of 20 mg dm-3 the reaction was much faster than for other investigated concentrations. The effect of the pH was tested in the range from 2 to 9. The optimal pH range was found to be between 6 and 9, but reaction was feasible also for lower pH. It can be concluded that investigated catalyst is applicable with high efficiency in the wide range of Oxone® dosages, dye concentrations and initial pH values

Catalytic properties of cobalt-doped alumina catalyst in oxone® activated degradation of orange G

Cobalt-doped alumina catalyst was synthetized using the sol-gel method, gelled and calcined at 500 °C. The synthesized material was previously fully characterized. Cobalt-doped alumina was tested as catalysts in an Orange G degradation in the presence of Oxone®. Oxone® is a precursor of radicals and the role of the investigated catalyst was to activate its decomposition. Sulfate ion radicals act as oxidizing species in dye degradation reaction. The influence of the mass of the catalyst and the reaction temperature was investigated. The catalyst mass and temperature increase were beneficial for the dye degradation rate. The pseudo-first order kinetic model was found to be the most appropriate fit for experimentally obtained data. The adsorption of the dye on Co-doped alumina was also tested, and it was found to be negligible. The investigated catalyst was found to be effective for Orange G degradation in the presence of Oxone®

Catalytic activity of pseudoboehmites impregnated with different cobalt contents in the oxidative degradation of tartrazine in the presence of Oxone

Pseudobemit je impregnisan kobaltom postupkom kapilarne impregnacije. Za impregnaciju su korišćene dve koncentracije, 3 mas% i 6 mas% Co 2+ u odnosu na masu pseudobemita. Dobijeni materijali su žareni na 500 ºC. Sintetisani katalizatori su ispitani u procesu oksidativne degradacije boje tartrazina u prisustvu Oksona kao izvora sulfatnih radikal anjona. Ispitivan je uticaj tempreature na efikasnost degradacije boje. Uočeno je da brzina degradacije raste sa porastom temperature. Eksperimentalno dobijeni rezultati su testirani korišćenjem najčešćih kinetičkih modela i dobijeno je da reakcija u svim slučajevima sledi brzinu pseudo-prvog reda. Takođe je uočeno da sa porastom sadržaja kobalta raste efikasnost katalizatora. Da bi se odredilo koja je reaktivna oksidativna vrsta dominantna u ispitivanom procesu, u reakcioni sistem je dodavan tercijalni butanol, odnosno etanol. Utvrđeno je da su sulfatni radikal anjoni dominantna reaktivna vrsta.Pseudoboehmite was impregnated with cobalt using a incipient wetness impregnation method. Two different concentrations of cobalt were used for impregnation: 3 mas% and 6 mas% of Co2+ relative to the mass of pseudoboehmite. The obtained materials were calcined at 500 ºC. The synthesized catalysts were tested in the process of oxidative degradation of tartrazine dye in the presence of Oxon as a source of sulfate anion radicals. The influence of temperature on the dye degradation efficiency was investigated. It was observed that the degradation rate increases with the increasing of temperature. The experimentally obtained results were tested using the most common kinetic models and it was found that the reaction follows a pseudo-first order rate in all cases. It was also observed that with an increase in the cobalt content, the efficiency of the catalyst increases. In order to determine which reactive oxidative species is dominant in the investigated process, tertiary buthalnol and ethanol was added to the reaction system. According to the experimental results sulfate anion radicals were found to be the dominant reactive species