Due to the usual resistance of textile dyes to conventional biological treatment processes, the color removal of dyeing wastewaters remains a challenge for the textile industry. This work evaluates the capacity of advanced oxidation processes based on thermally-activated persulfate concerning textile dyes’ degradation in aqueous solution and the reuse of dyeing baths. Preliminary studies were carried out in a bench-scale jacketed reactor, using Reactive Black 5 (40 mg L−1) as a model dye. Almost complete dye degradation was observed in 60 min in this stage, using 300 mg L−1 of persulfate and activation temperatures of 80 ºC, basically due to the action of radical sulfate. The use of high concentrations of persulfate (1000 mg L−1) allowed efficient color removal of dyeing baths containing remazol dyes in processes activated at 80 and 90 ºC. However, the wastewaters treated under these conditions did not lead to high dyeing efficiency in reuse studies, probably due to residual persulfate presence. In contrast, low concentrations of persulfate (250 mg L−1) lead to partial color removal and a better dyeing quality. The results suggest a good potential for treating high-temperature dyeing baths, saving water and auxiliary agents used in textile dyeing processes.

Neste trabalho descrevemos a preparação e a caracterização espectroscópica [ressonância paramagnética eletrônica (EPR), espectroscopia UV-Vis e espectroscopia de infravermelho com transformada de Fourier (FTIR)], magnética e espectroeletroquímica do complexo [MnII2(tidf)(OAc)(ClO4)(MeOH)] (tidf = ligante macrocíclico do tipo Robson, obtido pela condensação entre 2,6-diformil-4-metilfenol e 1,3-diaminopropano). O composto [MnII2(tidf)(OAc)(ClO4)(MeOH)] exibe antiferromagnetismo fraco e constante de acoplamento magnético J = -1.59(1) cm-1. A oxidação de [MnII2(tidf)(OAc)(ClO4)(MeOH)] monitorada por experimentos de espectroeletroquímica de UV-Vis e de EPR produziu espécies de valência mista Mn2(II/III) com perfil espectral semelhante ao do complexo [MnII MnIII(tidf)Br3(H2O)2]. Tentativas de cristalização de [MnII2(tidf)(OAc)(ClO4)(MeOH)] produziram o complexo trinuclear de manganês [Mn3III/II/III(tidf)2(µ-OAc)2](ClO4)2. O composto possui duas unidades [MnIII(tidf)]+ onde o íon metálico é pentacoordenado e conectadas a um íon central de MnII hexacoordenado através de pontes µ-fenolato e µ-acetato.

Synthesis, spectroscopic [electron paramagnetic resonance (EPR), UV-Vis and Fourier transform infrared spectroscopy (FTIR)], magnetic and spectroeletrochemical properties of [MnII2(tidf)(OAc)(ClO4)(MeOH)] (tidf = a Robson type macrocyclic ligand obtained through condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane) are reported. Compound [MnII2(tidf)(OAc)(ClO4)(MeOH)] shows a weak antiferromagnetic behavior with exchange coupling constant J = -1.59(1) cm-1. UV-Vis and EPR spectroelectrochemical response after oxidation of complex [MnII2(tidf)(OAc)(ClO4)(MeOH)] detected the stabilization of mixed-valence Mn2(II/III) species in solution showing spectral features similar to the ones of the isolated mixedvalence [MnII MnIII(tidf)Br3(H2O)2] compound. Crystallization of [MnII2(tidf)(OAc)(ClO4)(MeOH)] surprisingly produced the trimanganese complex [Mn3III/II/III(tidf)2(µ-OAc)2](ClO4)2, not observed in solution. It contains two pentacoordinated [MnIII(tidf)]+ units, each one connected to a central hexacoordinated MnII ion through one µ-phenolate and one µ-acetate bridge.

Dois complexos contendo vanádio e lítio, [V6Li10O8(ONep)14{OSi(Me)2(ONep)2}] (1)e [V(ONep)3(µ-ONep)2Li(thf)2] (2), Nep = neopentila, Me = metila e thf = tetraidrofurano, foram isolados em alto rendimento e caracterizados por diversas técnicas incluindo espectroscopias de ressonância paramagnética eletrônica (RPE, banda X) e ressonância magnética nuclear (RMN) de 29Si, medidas de susceptibilidade magnética e difratometria de raios X de monocristal. A despeito das condições similares de preparação, os dois produtos apresentam características estruturais admiravelmente distintivas: o complexo binuclear não-oxo 2é um simples produto de adição de "V(ONep)4" e "Li(ONep)(thf)2", enquanto 1é um agregado de valência mista com 16 centros metálicos. O oxoalcóxido molecular 1também contém grupos silanolatos, {OSi(Me2)(ONep)}-, produzidos por ataque nucleofílico de neopentóxidos à graxa de silicone dissolvida acidentalmente no meio de reação.Ambos os produtos têm aplicações promissoras em síntese orgânica e inorgânica, incluindo a preparação de óxidos mistos pouco comuns contendo vanádio, lítio e/ou silício.

Two complexes containing both vanadium and lithium, [V6Li10O8(ONep)14{O2Si(Me)2(ONep)}2] (1) and [V(ONep)3(µ-ONep)2Li(thf)2] (2), Nep = neopentyl, Me = methyl and thf = tetrahydrofuran, have been isolated in high yield and characterised by a number of techniques including X-band electron paramagnetic resonance (EPR) and 29Si{¹H} nuclear magnetic resonance (NMR) spectroscopies, magnetic susceptibility measurements and single crystal X-ray diffractometry. Despite the similar preparation conditions, the two products present remarkably distinctive structural features: complex 2is a binuclear adduct of "V(ONep)4" and "Li(ONep)(thf)2", while 1is a mixed-valence, 16-metal aggregate. The large molecular oxoalkoxide 1also contains silanolate units, {OSi(Me2)(ONep)} -, produced by nucleophilic attack of neopentoxide groups on Si-O bonds of silicone grease accidentally dissolved in the reaction media. Both products have promising applications in organic and inorganic synthesis, including the preparation of uncommon V-Li and/or Si containing oxides.