In this study, an aluminosilicate residue from insulators of high voltage transformers was used for the adsorption of basic dyes. The absorbent was characterized by X-ray fluorescence analysis, X-ray diffraction analysis, scanning electron microscopy, multimolecular adsorption theory (Branauer-Emmet-Teller (BET)) and determination of the point of zero charge (pHPZC). The effect of solution pH and adsorbent mass, the kinetic and thermodynamic behavior at different temperatures and the application of non-linear isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushevich were investigated. The pHPZC value for the aluminosilicate was 3.7. The best conditions for adsorption of methylene blue and crystal violet dyes were pH 8.0 and adsorbent mass of 1100 mg in 25 mL. The best fit for the experimental data was obtained applying the pseudo-second-order kinetic model, with an equilibrium time of 480 to 720 min, and the activation energy suggests a physical adsorption mechanism. Isothermal parameters suggest a heterogeneous, favorable and predominantly physical surface adsorption. The thermodynamic studies indicated that the adsorption process is not spontaneous and is exothermic and the Gibbs energy values (∆Gº) suggest physisorption.

ABSTRACT Purpose This study aimed to elaborate a hydrogel constituted by carboxymethyl chitosan (CMC), hyaluronic acid (HA) and silver (Ag) and to evaluate its healing effect on partial-thickness burn wounds experimentally induced in rats. Methods CMC was obtained by chitosan reacting with monochloroacetic acid. The carboxymethylation was confirmed by Fourier-transform infrared spectroscopy and hydrogen nuclear magnetic resonance (NMR). Scanning electron microscopy was used to determine the morphologicalcharacteristics of chitosan and CMC. After the experimental burn wound induction, the animals (n = 126) were treated with different CMC formulations, had their occlusive dressings changed daily and were followed through 7, 14 and 30 days. Morphometric, macroscopic and microscopic aspects and collagen quantification were evaluated. Results Significative wound contraction, granulation tissue formation, inflammatory infiltration and collagen fibers deposit throughout different phases of the healing process were observed in the CMC hydrogels treated groups. Conclusions The results showed that, in the initial phase of the healing process, the most adequate product was the CMC/HA/Ag association, while in the other phases the CMC/HA association was the best one to promote the healing of burn wounds.

The fact that alpha- and beta-chitin adopt different arrays in the solid state is explored to emphasize their different properties and distinct spectral characteristics and X ray diffraction patterns. The methods for their extraction from the biomass in view of the preservation of their native structures and aiming to fulfill the claims of purity and uniformity for potential applications are discussed. The different arrays adopted by alpha- and beta-chitin also result in distinct reactivities toward the deacetylation reaction. Thus, the deacetylation of beta-chitin is more efficient owing to the better accessibility to amide groups due to the lower crystallinity of this polymorph.

As reações diretas entre [Ru(NH3)5(H2O)](PF6) 2 (1) e P(m-tol)3 (a), P(p-tol)3 (b) e P(OC5H11)3 (c) forneceram os complexos [Ru(NH3)5P(m-tol)3](PF 6)2 (2a), trans-[Ru(NH3)4{P(p- tol)3}2](PF6)2 (3b) e trans-[Ru(NH3)4{P(OC5H 11)3}2](PF6)2 (3c), respectivamente. A constante de velocidade específica de substituição da amônia em (2a) foi de 4,3 x 10-3 s-1 (25 ºC, μ = 0,10 mol L-1). Os aquo complexos trans-[Ru(NH3)4(L)(H2O)]2+ (L = P(p-tol)3, 4b; L = P(OC5H11)3, 4c) foram gerados pela aquação térmica de uma das moléculas de L, dos respectivos complexos trans-[Ru(NH3)4L2 ]2+ (L = P(p-tol)3, 3b; L = P(OC5H11)3, 3c) e os valores das constantes foram: k-1 = 2,7 x 10-3 s-1 e k-1 = 3,5 x 10-3 s-1, respectivamente. Os valores dos potenciais formais de redução para 3b, 3c e 2a foram 0,50 ± 0,01V; 0,48 ± 0,01V e 0,50 ± 0,02V, respectivamente (vs SCE) [μ = 0,10 mol L-1; NaCF3COO; C H+ = 1,0 x 10-3 CF3COOH]. As reações: <IMG SRC="http:/img/fbpe/jbchs/v13n5/12819x1.gif" > foram estudadas e os valores de k1, k-1 e Keq foram 0,28 mol-1 L s-1, 0,06 s-1, 4,67 mol-1 L [para L = P(m-tol)3, 4a]; 0,25 mol-1 L s-1, 0,04 s-1, 6,25 mol-1 L [para L = P(p-tol)3, 4b] e 12,4 mol-1 L s-1, 5,8 x 10-1 s-1, 21 mol-1 L [para L = P(OC5H11)3, 4c] [25ºC; μ = 0,10 mol L-1; NaCF3COO; C H+ = 1,0 x 10-3 CF3COOH].

Direct reactions between [Ru(NH3)5(H2O)](PF6) 2 (1) and P(m-tol)3 (a), P(p-tol)3 (b) and P(OC5H11)3 (c) lead the complexes [Ru(NH3)5P(m-tol)3](PF 6)2 (2a), trans-[Ru(NH3)4{P(p -tol)3}2](PF6)2 (3b) and trans-[Ru(NH3)4{P(OC5H 11)3}2](PF6)2 (3c) respectively. These complexes have been isolated as hexafluorophosphate salts and characterized by elemental analysis, cyclic voltammetry and UV-VIS spectra measurements. One ammonia ligand in 2a is displaced at the a specific rate of 4.3 x 10-3 s-1 (25 ºC, μ = 0.10 mol L-1). The aquo species trans-[Ru(NH3)4(L)H2O]2+ (L = P(p-tol)3, 4b; L = P(OC5H11)3, 4c) are generated by the substitution of one L ligand with H2O, from trans-[Ru(NH3)4(L)2]2+ with k-1 = 2.7 x 10-3 s-1 [L = P(p-tol)3, 3b] and 3.5 x 10-3 s-1 [L = P(OC5H11)3 3c] (25 ºC, μ = 0.10 mol L-1) (NaCF3COO/CF3COOH; C H+ = 1.0 x 10-3 mol L-1). The formal reduction potentials for the species 3b, 3c and 2a are 0.50 ± 0.01V, 0.48 ± 0.01V and 0.50 ± 0.02V, respectively (vs SCE) [μ = 0.10 mol L-1 ; NaCF3COO; C H+ = 1.0 x 10-3 CF3COOH]. The following reactions: <IMG SRC="http:/img/fbpe/jbchs/v13n5/12819x2.gif"> [L = P(m-tol)3, P(p-tol)3 and P(OC5H11)3] were studied and the calculated values for k1, k-1 and Keq are 0.28 mol-1 L s-1, 0.06 s-1, 4.67 mol-1 L [L = P(m-tol)3, 4a]; 0.25 mol-1 L s-1, 0.04 s-1, 6.25 mol-1 L [L = P(p-tol)3, 4b]; 12.4 mol-1 L s-1, 5.8x10-1 s-1, and 21 mol-1 L [L = P(OC5H11)3, 4c], [25.0 ± 0.2 ºC; m = 0.10 mol L-1; NaCF3COO; C H+ = 1.0 x 10-3 CF3COOH].

Quitosanas comercial e purificadas nas formas neutra, acetato e cloridrato foram caracterizadas e comparadas quanto a solubilidade, hidrofilicidade, morfologia de suas superfícies e cristalinidade. As amostras bruta e purificada na forma neutra apresentam características e propriedades semelhantes, mas as formas salinas, principalmente cloridratos de quitosana, são diferentes. As morfologias das superfícies da amostra comercial e das formas purificadas são semelhantes, mas cloridrato de quitosana obtido por liofilização apresenta poros que não são observados nas outras amostras. Quitosanas comercial e purificada na forma neutra não são solúveis em água, mas acetato de quitosana é parcialmente solúvel. Essas três formas de quitosana apresentam hidrofilicidades e cristalinidades semelhantes, mas nos casos dos cloridratos a presença de cargas e de contra-íons provenientes de um ácido forte aumenta a hidrofilicidade, confere hidrossolubilidade e altera significativamente as interações inter e intracadeias, modificando o empacotamento no estado sólido e resultando em importante decréscimo de cristalinidade. No caso de acetato de quitosana é observado que os cristalitos são menores, o que pode ser atribuído à protonação parcial dos grupos amino e à presença de ânions acetato.

Commercial chitosan is purified in the neutral form and as chitosan acetate and chitosan hydrochloride. These samples were characterized and compared with respect to solubility, hydrophilicity, surface's morphology and crystallinity. Commercial chitosan and its neutral purified form present similar characteristics and properties but the saline purified forms, mainly the chitosan hydrochlorides, are quite different from them. The surface morphologies of the former samples are similar but that of the lyophilized chitosan hydrochloride presents pores which are not observed in the other samples. Commercial chitosan and its neutral purified form are not soluble in pure water but chitosan acetate is partially soluble. These samples present similar hydrophylicities and crystallinities but in the cases of the chitosan hydrochlorides the presence of charges and of counter ions from a strong acid enhances the hydrophilicity, promotes solubility in water and significantly alters the interactions inter and intrachains, modifying the packing in the solid state and drastically reducing the crystallinity. In the case of chitosan acetate it is observed that the crystallites are smaller probably due to the partial protonation of amine groups and to the presence of acetate anions.

Reações de desacetilação de quitina comercial em suspensão aquosa de hidróxido de sódio foram realizadas em etapa única de 6 horas a 115°C. Os efeitos de aditivos (boro hidreto de sódio ou antraquinona) e de borbulhamento de gases inertes (nitrogênio ou argônio) sobre as características das amostras desacetiladas foram avaliados. A espectroscopia de ressonância magnética nuclear de hidrogênio e viscosimetria capilar foram empregadas para determinações de graus médios de acetilação e de viscosidades intrínsecas de quitosanas, respectivamente. A difração de raiosX foi empregada para comparar as amostras quanto à cristalinidade e os espectros no infravermelho foram comparados para avaliar modificações estruturais decorrentes da reação de desacetilação. As quitosanas mais cristalinas foram obtidas quando um dos gases inertes foi borbulhado no meio durante a reação de desacetilação. Amostras ligeiramente mais desacetiladas foram obtidas na ausência de qualquer aditivo, mas severa despolimerização ocorreu nesses casos. A adição de boro hidreto de sódio ao meio reacional reduziu significativamente a despolimerização, mas a presença de antraquinona e o borbulhamento de nitrogênio, ou de argônio, não surtiu qualquer efeito, sugerindo que a presença de oxigênio não é um pré-requisito para a ocorrência de despolimerização.

Deacetylation reactions of commercial chitin were carried out in aqueous sodium hydroxide solution at 115°C for 6 hours. The effect from additives (sodium borohydride or anthraquinone) and of bubbling inert gas (nitrogen or argon) on the characteristics of deacetylated samples were evaluated. Average degrees of acetylation and intrinsic viscosity were determined by ¹H NMR spectroscopy and capillary viscometry, respectively. X-ray diffraction was employed to evaluate changes in crystallinity and infrared spectroscopy was used to monitor structural changes due to deacetylation. The bubbling of inert gas during the deacetylation reaction resulted in more crystalline samples of chitosan. Deacetylations carried out without any additive produced slightly more deacetylated chitosans but they were severely depolymerized. The depolymerization process was much less important when sodium borohydride was added to the reaction medium but the addition of anthraquinone and the bubbling of nitrogen, or argon, did not have any effect, this suggests that oxygen is not required for depolymerization.

RESUMO: Procedimentos adequados para as purificações de quitosana comercial como cloridrato e na forma neutralizada são descritos. As amostras obtidas apresentam elevado grau de pureza e baixo teor de cinzas conforme verificado através de termogravimetria. As determinações de graus de acetilação por espectroscopia de ressonância magnética nuclear (<img width=32 height=32 src="http://img/fbpe/po/v8n4/8292s1.gif" align=absmiddle > ou = 23,6%) e por titulações (<img width=32 height=32 src="http://img/fbpe/po/v8n4/8292s1.gif" align=absmiddle > ou = 23,0%) apresentam muito boa concordância. O cloridrato de quitosana é solúvel em água, o que permite determinações de viscosidade intrínseca em solventes aquosos na ausência de excesso de ácido e facilita a comparação de quitosana com outros polieletrólitos quanto a estimativas de rigidez/flexibilidade.

ABSTRACT: The procedures for the purification of a commercial chitosan as a hydrochloride and in the neutralized form are described. By applying these procedures, pure chitosans of low ash contents are obtained as determined by thermogravimetry. The agreement between the values of degrees of acetylation determined by conductimetric titrations (<img width=32 height=32 src="http://img/fbpe/po/v8n4/8292s4.gif" align=absmiddle > or = 23,0%) and by ¹H nmr spectroscopy (<img width=32 height=32 src="http://img/fbpe/po/v8n4/8292s4.gif" align=absmiddle > or = 23,6%) is very good. Chitosan hydrochloride being soluble in pure water allows the determination of intrinsic viscosity in dilute acid-free aqueous solutions and makes easier the comparison of chitosan and other polyelectrolytes with respect to their chain rigidity/flexibility.