RESUMO
This work describes the electrochemical degradation of Reactive Black 5 (RB5) by two methods: electrochemical and photo-assisted electrochemical degradation with and without a Fenton reagent. Two anodes were used, Pt and boron-doped diamond (BDD, 2500â¯ppm), and the cathode was 3% MnO2 nanoflowers (NFMnO2) on a carbon gas diffusion electrode (GDE). An electrochemical cell without a divider with a GDE with 3% w/w NFMnO2/C supported on carbon Vulcan XC72 was used. The decolorization efficiency was monitored by UV-vis spectroscopy, and the degradation was monitored by Total Organic Carbon (TOC) analysis. For dissolution monitoring, aliquots (1â¯mL) were collected during the degradation. After 6â¯h of H2O2 electrogeneration, the manganese concentration in the RB5 solution was only 23.1⯱â¯1.2⯵gâ¯L-1. It was estimated that approximately 60⯵gâ¯L-1 (<0.2%) of manganese migrated from the GDE to the solution after 12â¯h of electrolysis, which indicated the good stability of the GDE. The photoelectro-Fenton-BDD (PEF-BDD) processes showed both the best color removal percentage (â¼93%) and 91% of mineralization. The 3% NFMnO2/C GDE is promising for RB5 degradation.
Assuntos
Corantes/química , Eletrólise , Peróxido de Hidrogênio/química , Ferro/química , Compostos de Manganês/química , Naftalenossulfonatos/química , Óxidos/química , Poluentes Químicos da Água/química , Boro/química , Corantes/isolamento & purificação , Diamante/química , Eletrodos , Naftalenossulfonatos/isolamento & purificação , Oxirredução , Poluentes Químicos da Água/isolamento & purificaçãoRESUMO
Natural pozzolan is an amorphous silicate-based material of volcanic origin. In this work, the natural pozzolan was modified by using 3-aminopropyltriethoxysilane (APTES) as a grafting agent. This material was characterized by pHpzc, N2 adsorption/desorption curves, FTIR, TGA/DTG, DRUV, SEM, and elementary analysis. The functionalized materials were used for the removal of Reactive Black 5 (RB-5) and Brilliant Green 1 (BG-1) dyes from aqueous solutions using batch-contact adsorption. The characterization of modified pozzolan by FTIR, TGA/DTG, BET, and DRUV-vis revealed the effectiveness of grafting of amine functional group on pozzolan structure. The kinetic adsorption data were better fitted with general order for both dyes while for equilibrium models were better fitted by the Liu isotherm model. The maximum sorption capacities Q max (at 50 °C) obtained with the modified pozzolan were 350.6 and 300.9 mg g-1 for BG-1 and RB-5, at pH 9.0 and 2.0, respectively. The thermodynamic parameters show that the removal of dyes was spontaneous and endothermic. The modified material was also tested for the treatment of simulated dye house effluents showing very high efficiency.
Assuntos
Naftalenossulfonatos/isolamento & purificação , Propilaminas/química , Compostos de Amônio Quaternário/isolamento & purificação , Silanos/química , Adsorção , Corantes/química , Concentração de Íons de Hidrogênio , Cinética , Soluções , Termodinâmica , Água , Poluentes Químicos da Água/químicaRESUMO
Physical and thermal treatment was used to inactivate Trametes sp. SC-10 fungus. The resulting biomass was named BTV, characterized by analytical techniques such as SEM, EDX, FTIR, BET, and Barrett-Joyner-Halenda (BJH) model. pH, kinetic, and equilibrium adsorption studies with the Acid Blue 161 (AB-161) dye were investigated at 303.15 K. The kinetics of the biosorption process were examined at 600.00 and 1300 mg L-1, using pseudo-first-order, pseudo-second-order, and Avrami fractional-order models. The maximum biosorption capacity of BTV for AB-161 dye was 221.6 mg g-1. Considering the biosorption data and the functional groups of BTV, it can be inferred that the sorption mechanism of AB-161 is regulated by electrostatic interactions between ionized dye molecules and negative charges on BTV in an aqueous solution. Finally, the BTV was tested with a simulated effluent with 89.47% efficiency, presenting the BTV as a biosorbent for real effluents polluted with dyes.
Assuntos
Biomassa , Corantes/isolamento & purificação , Complexos de Coordenação/isolamento & purificação , Naftalenossulfonatos/isolamento & purificação , Trametes , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , CinéticaRESUMO
This study presents an attempt to solve two serious environmental problems: the generation of toxic effluents and solid waste disposal. The work proposes recycling cigarette filters with the purpose of degrading reactive dyes, which are used in the textile industry. Filters of smuggled cigarettes were recycled through Fe3+ immobilization on their surface. The material obtained was characterized through Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and ultraviolet-visible spectroscopy (UV-vis). The factorial design revealed that the most suitable conditions for the degradation of Reactive Black 5 dye were obtained by using 1 g of material at pH 3.0 in a 100 mg L-1 hydrogen peroxide solution. The material showed excellent performance in the Reactive Black 5 dye degradation process; in 60 min, 99.09 % dye was removed. At pH 7.0, the dye degradation was 72.67 %, indicating that the material prepared can be used at pH values greater than 3.0 without the occurrence of hydrated Fe3+ oxide precipitation. Furthermore, the material showed no loss of catalytic activity after three degradation studies.
Assuntos
Filtração/métodos , Naftalenossulfonatos , Poluentes Químicos da Água , Purificação da Água/métodos , Compostos Férricos/química , Resíduos Industriais , Naftalenossulfonatos/análise , Naftalenossulfonatos/química , Naftalenossulfonatos/isolamento & purificação , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificaçãoRESUMO
This paper reports a green and efficient procedure for extraction of the dyes Malachite Green (MG), Methylene Blue (MB), and Reactive Red 195 (RR) using an aqueous two-phase system (ATPS). An ATPS consists mainly of water, together with polymer and salt, and does not employ any organic solvent. The extraction efficiency was evaluated by means of the partition coefficients (K) and residual percentages (%R) of the dyes, under different experimental conditions, varying the tie-line length (TLL) of the system, the pH, the type of ATPS-forming electrolyte, and the type of ATPS-forming polymer. For MG, the best removal (K = 4.10 × 10(4), %R = 0.0069%) was obtained with the ATPS: PEO 1500 + Na2C4H4O6 (TLL = 50.21% (w/w), pH = 6.00). For MB, the maximum extraction (K = 559.9, %R = 0.258%) was achieved with the ATPS: PEO 400 + Na2SO4 (TLL = 50.31% (w/w), pH = 1.00). Finally for RR, the method that presented the best results (K = 3.75 × 10(4), %R = 0.237%) was the ATPS: PEO 400 + Na2SO4 (TLL = 50.31% (w/w), pH = 6.00). The method was applied to the recovery of these dyes from a textile effluent sample, resulting in values of K of 1.17 × 10(4), 724.1, and 3.98 × 10(4) for MG, MB, and RR, respectively, while the corresponding %R values were 0.0038, 0.154, and 0.023%, respectively. In addition, the ATPS methodology provided a high degree of color removal (96.5-97.95%) from the textile effluent.
Assuntos
Fracionamento Químico/métodos , Corantes/isolamento & purificação , Indústria Têxtil , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Compostos Azo/química , Compostos Azo/isolamento & purificação , Cor , Corantes/química , Azul de Metileno/química , Azul de Metileno/isolamento & purificação , Naftalenossulfonatos/química , Naftalenossulfonatos/isolamento & purificação , Corantes de Rosanilina/química , Corantes de Rosanilina/isolamento & purificação , Cloreto de Sódio/química , Solventes/química , Águas Residuárias/química , Poluentes Químicos da Água/químicaRESUMO
Sludge from the textile industry was used as a low-cost adsorbent to remove the dye Reactive Red 2 from an aqueous solution. Adsorbents were prepared through the thermal and chemical treatment of sludge originating from physical-chemical (PC) and biological (BIO) effluent treatment processes. The adsorbent characterization was carried out through physical-chemical analysis, X-ray fluorescence (XRF) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, pHPZC determination, Boehm titration method, Brunauer-Emmett-Teller (BET) surface area analysis and scanning electron microscopy (SEM). Batch kinetic experiments and adsorption isotherm modeling were conducted under different pH and temperature conditions. The results for the kinetic studies indicate that the adsorption processes associated with these systems can be described by a pseudo-second-order model and for the equilibrium data the Langmuir model provided the best fit. The adsorption was strongly dependent on the pH but not on the temperature within the ranges studied. The maxima adsorption capacities were 159.3 mg g(-1) for the BIO adsorbent and 213.9 mg g(-1) for PC adsorbent at pH of 2 and 25 °C.
Assuntos
Naftalenossulfonatos/isolamento & purificação , Esgotos/química , Indústria Têxtil , Triazinas/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Poluição Química da Água/prevenção & controle , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Naftalenossulfonatos/química , Concentração Osmolar , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Triazinas/química , Poluentes Químicos da Água/químicaRESUMO
The adsorption of SPADNS (trisodium salt of 2-(p-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid) onto resins XAD 2, XAD 7 and silica gel was studied in the presence and in the absence of the cationic surfactant CTAB (cetyl trimethylammonium bromide). At a ratio of 2.5 CTAB to 1 SPADNS, the surfactant caused a marked increase in SPADNS adsorption. The experimental results for adsorption versus time were applied on the basis of three kinetic models (pseudo-first-order Lagergren, pseudo-second-order, and intraparticle diffusion). The interaction between CTAB and SPADNS was investigated using spectrophotometric, conductometric, and computational techniques. Theoretical results point to the formation of an ion pair between CTAB and SPADNS that influences the solution spectra, in agreement with conductometric and spectrophotometric data.
Assuntos
Resinas Acrílicas/química , Compostos Azo/isolamento & purificação , Compostos de Cetrimônio/química , Naftalenossulfonatos/isolamento & purificação , Poliestirenos/química , Tensoativos/química , Adsorção , Compostos Azo/química , Cetrimônio , Cinética , Simulação de Dinâmica Molecular , Naftalenossulfonatos/química , Sílica Gel/químicaRESUMO
The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO(2) P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO(2) used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO(2) reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.