Luiz C.G. Vasconcellos

Adsorption of polycyclic aromatic hydrocarbons from aqueous solutions by modified periodic mesoporous organosilica

A novel procedure was developed for the synthesis of a periodic mesoporous organosilica (PMO), which was used to remove polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. Adsorption equilibrium isotherms and adsorption kinetics experiments were carried out in solutions of PAHs (2-60 mg L(-1)), using the PMO as adsorbent. Adsorption models were used to predict the mechanisms involved. The adsorption kinetics data best fitted the pseudo-first-order kinetic model for naphthalene, and to the pseudo-second-order model for fluorene, fluoranthene, pyrene, and acenaphtene. The intraparticle model was also tested and pointed to the occurrence of such processes in all cases. The isotherm models which best represented the data obtained were the Freundlich model for fluoranthene, pyrene, and fluorene, the Temkin model for naphthalene, and the Redlich-Peterson model for acenaphtene. PAHs showed similar behavior regarding kinetics after 24 h of contact between adsorbent and PAHs. FTIR, XRD, BET, and SEM techniques were used for the characterization of the adsorbent material.

Adsorption of BTX (benzene, toluene, o-xylene, and p-xylene) from aqueous solutions by modified periodic mesoporous organosilica

The capacity of a periodic mesoporous organosilica (PMO) to adsorb the aromatic compounds benzene, toluene, o-, and p-xylenes (BTX), which are usually present in produced waters, was investigated under both column and batch processes. The PMO was synthesized by condensation of 1,4 bis(triethoxisilyl)benzene (BTEB) under acidic conditions by using structure-directing agent (SDA) Pluronic P123 in the presence of KCl. Thermogravimetric analysis showed that the presence of the surfactant decreases the thermal stability of the PMO. The small-angle X-ray diffraction pattern, as well as the nitrogen adsorption/desorption isotherm measurements, revealed that the synthesized material has a crystalline structure, with hexagonally-ordered cylindrical mesopores. The adsorption kinetics study indicated an adsorption equilibrium time of 50 min and also showed that the data best fitted the pseudo-first order kinetic model. The intraparticle diffusion model was also tested and pointed to the occurrence of such process in all cases. Both Langmuir and Temkin models best represented the adsorption isotherms of toluene; Langmuir and Redlich-Peterson models best represented the data obtained for the other compounds. Adsorption capacity decreases in the order benzene>o-xylene>p-xylene>toluene. Satisfactory results were observed in the application of the synthesized PMO for the removal of BTX from aqueous solution.

Structure and properties of iron–cyclam complex of 2-aminophenol

The cis-[Fe(cyclam)Cl2]Cl and trans-[Fe(cyclam)Cl2]BF4 complexes were prepared by a new synthetic procedure. These isomers were characterized by elemental analysis, electronic spectroscopy (lmax 238, 334 and lmax 238, 302 and 355 nm for cis- and trans-[Fe(cyclam)Cl2], respectively) and electrochemistry (E1:2 212 and 83 mV; vs. Ag AgCl, KCl 3.5 M, 25°C m0.1 M NaTFA, pH 3.0 for cis -a ndtrans-[Fe(cyclam)Cl2], respectively). The reaction of cis-[Fe(cyclam)Cl2] isomer with 2-aminophenol (catH3) ligand yields the cis-[Fe(cyclam)(qH)] 2 complex, where (qH) is the quinonoid oxidized form of the (catH3) ligand that is originated by an intramolecular electron transfer reaction. The cis-[Fe(cyclam)(qH)](PF6)2 complex crystallizes in the space group P21:n, with two different values for Fe‐N bond length, due to the s and p distinct contributions. The electrochemical analysis of this species shows three one-electron sequential processes: E1:2 (I) 316 mV, E1:2 (II) 361 mV and E1:2 (III)1.013 mV assigned to (sqH:catH3), (qH:sqH) and (Fe(III):Fe(II)) redox process, respectively.

The effect of polymeric additives on the solubilisation of a poorly-soluble drug in micellar solutions of Pluronic F127.

The solubilisation of griseofulvin in 1wt% aqueous micellar solutions of Pluronic F127 at 37°C has been modified by adding polyethylene glycol PEG 35000 or poly(vinylpyrrolidone) PVP K30. The solubilisation capacity expressed in terms of unit weight of F127 is increased by the addition of 0.5wt% PEG 35000 to a value approaching double that of a 2.5wt% solution of F127 alone, but there is no advantage in adding 0.5wt% PVP K30.

Thermal isomerization of cis-[Fe(cyclam)Cl2]Cl·H2O complex in the solid state

Abstract The solid state thermal isomerization of cis -[Fe(cyclam)Cl 2 ]Cl·H 2 O (cyclam is 1,4,8,11-tetraazacyclotetradecane), is investigated by TG/DSC, electrochemical and vibrational spectroscopic methods. The thermal isomerization of this complex was found to be water dependent and endothermic. An aquation–anation pathway that precedes the macrocyclic ligand stereochemical rearrangement in the complex is proposed.

Properties of triethylphosphite complexes of pentacyanoferrate(II) and (III). Cyanide photolabilization in a pentacyanoferrate(II) complex with a monodentate ligand

Abstract Na 3 [Fe(CN) 5 P(OCH 2 CH 3 ) 3 ] was synthesized and characterized by electronic (λ max =320 nm ( 1 A 1 → 1 E), ϵ=314 M −1 cm −1 ) and IR spectroscopies, cyclic voltammetry ( E °′=0.40 V versus SCE) and elemental analysis. The Fe(III) species was synthesized by PbO 2 oxidation of the corresponding [Fe(CN) 5 P(OCH 2 CH 3 ) 3 ] 3− complex ion. The [Fe(CN) 5 P(OEt) 3 ] 2− and [Fe(CN) 5 P(OEt) 3 ] 3− species do not undergo aquation reactions for a period of at least three weeks. Irradiation of the complex ion [Fe(CN) 5 P(OCH 2 CH 3 ) 3 ] 3− in aqueous solutions with light of 313 nm leads to phosphite and cyanide aquations, with quantum yields φ CN ≅0.08 and φ P(OEt) 3 ≅0.13 mol/einstein, respectively.

Synthesis and characterization of dinuclear complexes of 3,3′,4,4′-tetraminobiphenyl with tetramminoruthenium and bis(bipyridine)ruthenium residues and their two- and four-electron oxidized products including a ZINDO study of orbital mixing as a function of ligand oxidation state†

This paper reports the synthesis, characterisation and reactivity of new complexes of ruthenium, the symmetric dinuclear complex of ruthenium tetrammine [(Ru(NH3)4)2(catH4·catH4)](PF6)4 and the asymmetric dinuclear complex of ruthenium bis(bipyridine) and ruthenium tetrammine [Ru(NH3)4(catH4·catH4)Ru(bpy)2](PF6)4 where (catH4·catH4) represents the bridging ligand 3,3′,4,4′-tetraminobiphenyl. These complexes can be oxidized to the two-electron oxidized ligand mixed valence (qH2·catH4) species and the four-electron oxidized ligand (qH2·qH2) species. Further oxidation yields a range of Ru(III) species. These complexes were studied by proton NMR, UV–VIS spectra, cyclic voltammetry and ZINDO/1 and ZINDO/S calculations.

N-octane catalytic isomerization with aluminium and aluminiumlanthanum pillared nontronite

Nontronite samples pillared with aluminium (Pt/Al-PilM) and aluminium-lanthanum (Pt/AlLa-PilM) were prepared from natural nontronite, characterized and tested as catalyst in n-octane hydroisomerization reaction. The results were compared with those obtained from the same reaction using commercial Y-zeolite impregnated with platinum (Pt-Y). Experiments with commercial zeolite show that platinum is essential to maintain the reactional selectivity of the products. The conversion capacities of (Pt/Al- PilM) and (Pt/AlLa-PilM) were 70% and 40%, respectively, surpassing the Pt-Y performance of 30%, but with the same selectivity. X-ray diffraction data show that organic matter oxidation followed by cationic homogenization is of paramount importance for pillared clay preparation.