Navegando por Assunto "Corantes"

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Acesso aberto (Open Access)
Adsorção de corantes básicos empregados na indústria têxtil por argila: cinética e perfil de equílibrio
(Universidade Federal do Pará, 2015-10-14) AZEVEDO, Luiz Eduardo Chaves de; VIEIRA, Melissa Gurgel Adeodato; http://lattes.cnpq.br/6611289393148830; CARVALHO, Samira Maria Leão de; http://lattes.cnpq.br/6192858937057152
In this work, the adsorption of textile basic dyes by clay was studied in aqueous solutions and batch system. Clay was obtained from Icoaraci, metropolitan region of Belém, Pará (Brazil) and was used without treatment (A-BRU) and treated by sedimentation (A-TRA). The basic dyes studies were: Basic Yellow 28, Basic Blue 26 (Blue Victory), Basic Yellow 02 (Auramine), Basic Red 01 (Rhodamine 6G) and Basic Orange 02. The clays were characterized by chemical (CTC and charge density), physical (particle size analysis, SBET and He picnometry), thermal (ATG and DTA), mineralogical and morphological analyses (XRD, SEM/EDS and FTIR). Adsorption experiments were carried out to investigate affinity between dyes and clays (qualitative test), initial concentration and pH effects of the dye solutions. The adsorption kinetics data were analyzed by theoretical models. The adsorption equilibrium data were fitted by Langmuir and Freundlich models. The thermodynamic parameters were calculated from adsorption equilibrium data at different temperatures. The concentration of clay particles in the A-TRA increased 100% after sedimentation. In the clay composition minerals as quartzo, kaolinite and illite /muscovite were identified. The SBET increased from the 22.38 m².g-1 (A-BRU) to 33.02 m².g-1 (A-TRA). Significant differences between the values of density and total pore volume of the clays were not observed. Comparatively, the CTC value of the A-TRA increased 300%. The clay surfaces are predominantly negatives, according to the charge density results (Q). There were no significant differences between the thermal analysis results of the samples. From the adsorption affinity tests the more reactive dyes were the Basic Yellow 2 (BY2) and Basic Blue 26 (BB26) and the adsorbent with improved performance was A-TRA. The adsorption kinetics data were well fitted by pseudo-second order (BY2/A-TRA) and intraparticle diffusion models (A-TRA/BB26). The adsorption equilibrium data were well fitted by Langmuir (BY2/A-TRA) and Freundlich (A-TRA/BB26) models. The parameters of the mathematic models indicated that the adsorption is favorable. The thermodynamic parameters showed that the adsorption processes investigated are spontaneous and endothermic.
Acesso aberto (Open Access)
Dye incorporation in polyphosphate gels: synthesis and theoretical calculations
(2003-06) DEL NERO, Jordan; GALEMBECK, André; SILVA, Sidicleia Bezerra Costa; SILVA, José Augusto Pereira da
In this work we described theoretical calculations on the electronic structure and optical properties of the dyes crystal violet and malachite green based in semiempirical methods (Parametric Method 3 and Intermediate Neglect of Differential Overlap / Spectroscopic - Configuration Interaction) and the synthesis of a new hybrid material based upon the incorporation of these dyes in an aluminum polyphosphate gel network. The samples are nearly transparent, free-standing thick films. The optical properties of the entrapped dyes are sensitive to chemical changes within the matrix caused either by gel aging or external stimulli such as exposition to acidic and basic vapors that can percolate within the matrix. Our theoretical modeling is in good agreement with the experimental results for the dyes.
Acesso aberto (Open Access)
Síntese, caracterização físico-química e aplicação de alumínossilicatos como adsorventes
(Universidade Federal do Pará, 2003-05) CASTRO, Elton Anderson Santos de; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
In this work three differente aluminosilicates were used for evaluation of the index of recovery of the coloring monovalent metilene blue. The no-porous clay mineral, Kaolinite, from Capim river area in Pará, Brazil, was treated with hydrochloric acid 5N in order to increase the specific area. The microporous molecular sieve, zeolite NaP, was synthesized through the hidrotermal method, with the kaolinite of Capim river area being used as source of Si and Al. The hidrotermal method was also used for the synthesis of the mesoporous molecular sieve Al-MCM-48, wich received thermal treatment (calcination) at 540ºC under flow of N2 and air for 7h to removal of the agent director (surfactant). The porous and no-porous materials were characterized by X-ray diffraction, infrared spectrophotometry, thermodifferential and termogravimetric analyses and adsorption and desorption methods with N2. Chemical analysis for the clay mineral has been performed and scanning electronic microscopy was used for the microporous aluminosilicate. These materials were tested as adsorbents in the recovery of the metilene blue at concentration of 6ppm, in different times (20, 40, 60 and 120min) with the contact method being used. The concentration, separation method of phases and the more appropriate wave length were studied. The determination of the recovery index for the organic coloring, using the three materials, was performed through visible spectrophotometry. XRD and chemical analysis results revealed the high purity of the clay mineral kaolinite. The specific surface area increased by 31,23% after acid activation. The specific area obtained for Al-MCM-48, was of 1219m2g-1, which is a characteristic value for this kind of materials. The results of XRD indicate that the zeolita NaP was formed, but traces of the feldspatoid hidroxysodalite are also present, what could be confirmed by the SEM images. The values of the recovery index for the metilene blue demonstrated that the kaolinite under acid activation was the most effective (100% of recovery), followed by the zeolite NaP (97,89% of recovery) and Al-MCM-48 (97,35% of recovery). The results indicate the viability of use of these materials as agents for pre-concentration in cromatographic analyses.