Characterization of hydrothermaly synthesized zirconia nanopowders

In this paper,a hydrothermal method for synthesis of zirconia nanopowders: pure and with incorporated Si4+ions is presented. Zirconyl chloride and tetraethyl orthosilicate were used as precursors. As prepared powders were annealed at 600 °C and their structural (XRD), morphological (TEM) and textural (BET method) properties were obtained.It has been shown that by using hydrothermal synthesis method pure monoclinic ZrO2highly crystalline powder can be obtainedwithcrystallites of about 25nm. Incorporation of Si4+ions induced stabilization of tetragonal crystalline phase at room temperature, decreasing particle sizes to about 3-6 nm and increasing specific surface area of nanopowders.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 201

Elektrohemijska oksidacija 2,4,6-trihlorfenola na nano-cirkonijum - oksidnoj matrici dopiranoj gvožđem

Solvothermaly synthesized zirconium oxide nanopowders, pure and doped with various amounts of iron ions (1–20 %), were used as modifiers of glassy carbon electrodes. The modified electrodes were tested in the reaction of electrochemical oxidation of 2,4,6-trichlorophenol (TCP) in order to inves tigate the influence of doping on electrochemical performance of zirconia mat rix. The techniques of cyclic voltammetry and electrochemical impedance spectroscopy were employed. Cyclic voltammetry showed that electrooxid ation of TCP proceeded through the oxidation of hydroxyl group. Possible pathway included the formation of quinones and the formation of polyphenol film on the electrode surface, leading to the electrode fouling. Iron doping enhanced the activity of zirconia matrix towards TCP electrooxidation. Elec trochemical impedance spectroscopy showed the importance of iron content in zirconia matrix for the preferable pathway of TCP electrooxidation. The quin one formation pathway was favoured by low iron doped zirconia (doped with 1% of iron), while polyphenol film formation on the electrode surface was more pronounced at samples with higher iron ion content (for doping with 10 and 20 % of iron). The sample with 5 % of added iron ions, showed intermedНанопрахови цирконијум-оксида, чисти и допирани различитим количинама јона гвожђа синтетисани су солвотермалном методом. Добијени прахови су коришћени као модификатори електродa од стакластог угљеника. Модификоване електроде су тести- ране у реакцији електрохемијске оксидације 2,4,6-трихлорфенола (TCP), како би се испитао утицај допанта на перформансе цирконијум-оксидне матрице. За испитивање су коришћене технике цикличне волтаметрије и електрохемијске импедансне спектро- скопије. Резултати цикличне волтаметрије су показали да се електрооксидација TCP одиграва преко оксидације хидроксилне групе. Могуће даље реакционе путање су укљу- чивале формирање хинона и настајање полифенолног филма на површини електроде који доводи до пасивације електроде. Допирање јонима гвожђа је повећало активност цирконијум-оксидне матрице за електрооксидацију TCP. Резултати електрохемијске импедансне спектроскопије су указали на утицај количине јона гвожђа у цирконијум- -оксидној матрици на реакциони механизам TCP електроосидације. Реакциона путања која укључује формирање хинона је фаворизована на цирконијум-оксидним електро- дама са ниским садржајем јона гвожђа (допираног са 1 % јона гвожђа), док је форми- рање полифенолног филма дошло до изражаја на узорцима са већим садржајем јона гвожђа (допираних са 10 и 20 % јона гвожђа). Узорак цирконијум-оксида, допиран са 5 % јона гвожђа, има прелазна својства, јер долази до формирања полифенолног филма на површини електроде, али и до његове разградње

Palladium sorption by aminofunctionalized macroporous copolymer from chloride–nitrate solutions

Macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) with attached diethylene triamine [PGME-deta] with high amino-group content was used for the investigation of the Pd(II) sorption kinetics from mixed chloride/nitrate aqueous solutions in acidic medium (pH 2.0) at T=298 K. Four kinetic models were employed in order to comprehend the mechanism of Pd(II) sorption. The maximum experimental Pd(II) sorption capacity at initial pH 2.0 and 298 K was 20 mg g-1

Sinteza, svojstva i primena umreženih makroporoznih kopolimera na bazi metakrilata

In this paper, the results obtained during extensive research on the synthesis, properties and application of cross linked copolymers, performed at the Faculty of Technology and Metallurgy (Department of Physical Chemistry and Electrochemistry) and at the IChTM (Center for Catalysis and Chemical Engineering and Center for Chemistry) are summarized. According to the obtained results, changes in the composition of the inert component and the content, type and amount of the crosslinking agent, as well as the type of copolymerization reaction, all strongly influence the porosity parameters of the synthesized macroporous copolymers. Also, it was shown that the synthesized copolymers of glycidyl methacrylate, GMA, and ethylene glycol dimethacrylate, EGDMA, modified with ethylene diamine can be used for the selective sorption of gold and platinum from mixed solutions containing copper, cobalt and nickel ions.U okviru ovoga rada prikazani su rezultati dobijeni u toku višegodišnjeg izučavanja sinteze, svojstava i primene makroporoznih umreženih kopolimera na bazi metakrilata, koja su obavljena pri Katedri za fizičku hemiju i elektrohemiju Tehnološko-metalurškog fakulteta u Beogradu, Centra za katalizu i hemijsko inženjerstvo i Centra za hemiju Instituta za hemiju, tehnologiju i metalurgiju u Beogradu. Pokazano je da se izmenom sastava i udela inertne komponente, vrste i udela umreživača, kao i načina izvođenja reakcije kopolimerizacije može bitno uticati na parametre porozne strukture sintetizovanih umreženih makroporoznih kopolimera i na taj način njihova svojstva prilagoditi različitim potrebama. Pokazano je takođe da se sintetizovani kopolimeri glicidilmetakrilata i etilenglikoldimetakrilata obrađeni sa etilendiaminom mogu uspešno koristiti za selektivno izdvajanje platine iz mešanih rastvora sa jonima bakra, kobalta i nikla

Electrochemical Behavior of H3pw12o40/Acid-Activated Bentonite Powders

Electrochemical behavior of 12-tungstophosphoric acid (HPW)/acid-activated bentonite (AAB) powders with various loadings of HPW was investigated. The physicochemical properties of the prepared powders were examined by X-ray powder diffraction, nitrogen adsorption-desorption isotherms, atomic force microscopy and cyclic voltammetry measurements. The results indicated that the prepared powders are composed mainly of oriented domains of large rock blocks, probably resulting from a preferable deposition of bentonite particles having a face-to-face interaction. The particles had a mainly disordered mesoporous structure with a pore volume that varied according to the pore size in the range of 2-50 nm. In addition, the particles had crystallite size between 4.9 and 9.0 nm. The electrocatalytic activities of prepared HPW/AAB electrodes were studied in the oxidation of NO2- and the results revealed that the electrodes possessed relatively higher nitrite oxidation currents than AAB electrode. The best electroactivity was observed for HPW3/AAB electrode (AAB + + 20 wt % HPW) and the limit of detection (3 sigma) was determined as 8 mu M

Nickel-doped alumina

Alumina powders, pure and doped with nickel, were synthesized by sol gel method and calcined at 500oC in order to obtain mesoporous structures with a high specific surface area, well adaptable to catalytic application. XRD analysis showed that the addition of Ni2+affect the structural properties of the synthesized oxides. In order to test electrochemical activity of introduced nickel GCE modified with synthesized material was tested in 0.1 M NaOH solution without and with methanol.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 201

Properties of activated alumina obtained by flash calcination of gibbsite

On exposing gibbsite, with granulation below 10 μm to flash calcination of 0.5 s in the regime of pneumatic transport and at temperatures above 883 K, a microcrystalline material with a high degree of amorphization was obtained, as established from data of XRD analysis. It was shown that at 883 K the mechanism of gibbsite dehydration changes with a decrease of the activation energy from 141 to 53 kJ/mol. The obtained activated alumina is characterized by a specific surface area of over 200 m2/g and a pore structure with micro- and mesopores developed in the inside of grains of the starting material

Kinetic of sintering of polyethilene glycol and lanthanum dopped aluminum oxide obtained by the sol-gel method

Sintering and crystallization of low-density polyethylene glycol (PEG) and lanthanum, La(III)-doped Al2O3 aerogels prepared from aluminum isopropoxide were investigated. The sintering behavior of non-doped and doped aerogels was examined by following the change of specific surface area with isothermal heat-treatment. The specific surface area and crystalline phases of non-doped and PEG+La(III)-doped aerogels were determined, and the effects of dopants on the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal sintering experiments showed that the sintering mechanism of non-doped and PEG+La(III)-doped Al2O3 aerogels is surface diffusion. The specific surface areas of alumina samples decrease rapidly during the initial period of sintering, and more slowly with prolonged sintering time. The change of the porous structure is correlated with the phase transformation of γ-Al2O3 during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3 aerogels came to about 20 m2g-1 with heat-treatment at 1100°C because of crystallization of α-Al2O3 after densification. In the case of heattreatment at 1200°C, the largest surface area was observed for PEG+La(III) doped Al2O3 aerogels and the XRD pattern showed only low ordered θ-Al2O3. These indicate that the addition of PEG+La(III) to boehmite sol prevents Al2O3 aerogels from sintering and crystallizing to the α-Al2O3 phase. Even after 20 h at 1000°C, PEG+La (III)-doped alumina samples maintain a rather good specific surface area (108 m2 g-1) in comparison to the non-doped, containing mainly θ-Al2O3 and minor amounts of δ-Al2O3. Aluminum-oxides with these structural and textural properties are widely used as a coatings and catalyst supports in the field of various catalysis

Zirconium dioxide nanopowders with incorporated Si4+ ions as efficient photocatalyst for degradation of trichlorophenol using simulated solar light.

We present a hydrothermal method for synthesis of zirconia nanopowders: pure and with incorporated Si4+ ions. Zirconyl chloride and tetraethyl orthosilicate were used as precursors. As prepared powders were annealed at 600 degrees C and characterized using structural (XRD), morphological (SEM and TEM) and optical techniques (UV/vis DR, FTIR and photoluminescence spectroscopy). Their textural properties (BET method) and photocatalytic activity toward degradation of model compounds (tricholophenol and Rhodamine B) using simmulated solar light were obtained. We showed that by using hydrothermal synthesis method pure monoclinic ZrO2 highly crystalline powder can be obtained. Incorporation of Si4+ ions induced stabilization of tetragonal crystalline phase at room temperature and decreasing of particle sizes. Incorporation of Si4+ ions in zirconia matrix also resulted in increase of specific area of nanopowders. FTIR measurements were used as proof for existence of Zr-O-Si bond. Effective band gap of zirconia powders was reduced from 5 (pure ZrO2) to 3.8 eV for samples with Si4+ ions. All zirconia powders showed significant photocatalytic activity regarding degradation of triclorophenol and no activity regarding RB (Rhodamine B dye). Photocatalytic activity of zirconia was increased by incorporation of Si ions in the host matrix. The source of this observation is discussed correlating all obtained properties of pure and Si-incorporated nanopowders. Optimization of synthesis parameters and composition of zirconia samples obviously can lead to their photocatalytic activity comparable to Degussa TiO2 powder, famous and commercial photocatalyst. (C) 2016 Elsevier B.V. All rights reserved

Metal sorption on macroporous poly(GMA-co-EGDMA) modified with ethylene diamine

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine (EDA). The samples were characterized by mercury porosimetry, FT-IR spectroscopy and elemental analysis. The sorption rate of the modified copolymer, poly(GMA-co-EGDMA)-en for Cu(II) ions determined under non-competitive conditions was relatively rapid, i.e. the maximum capacity was reached within 30 min. Batch sorption capacities for Cu(II), Fe(II), Mn(II), Cd(II), Zn(II), Pb(II), Cr(III) and Pt(IV) ions were determined under non-competitive conditions in the pH range 1.25-5.5 at room temperature. The maximum sorption capacities of poly(GMA-co-EGDMA)-en under non-competitive conditions were 1.30 mmol/g for Pt(IV) at pH 5.5, 1.10 mmol/g for Cu(II) at pH 5.5, 1.06 mmol/g for Pb(II) at pH 1.25 and 0.67 mmol/g for Cd(II) ions at pH 5.5. The selectivity of poly(GMA-co-EGDMA)-en towards Cu(II), Co(II), Ni(II), Pb(II) and Pt(IV) ions was investigated under competitive conditions. Poly(GMA-co-EGDMA)-en showed high selectivity for Pt(IV) over Cu(II), Co(II), Ni(II) and Pb(II) ions at pH 2.1. At pH 5.5, the metal sorption capacities of poly(GMA-co-EGDMA)-en decreased in the order: Cu(II) gt Co(II) gt Pt(IV) approximate to Ni(II) gt Pb(II). Regeneration of the Cu(II), Ni(H) and Pb(II) loaded poly(GMA-co-EGDMA)-en with 2 M HIS04 showed that the polymer can be reused in several sorption/desorption cycles