Avaliação do tratamento eletroquímico (direto e indireto) como alternativa de degradação do corante azul de metileno

Textile industry has been a cause of environmental pollution, mainly due to the generation of large volumes of waste containing high organic loading and intense color. In this context, this study evaluated the electrochemical degradation of synthetic effluents from textile industry containing Methylene Blue (AM) dye, using Ti/IrO2-Ta2O5 and Ti/Pt anodes, by direct and indirect (active chlorine) electrooxidation. We evaluated the influence of applied current density (20, 40 and 60 mA/cm2 ), and the presence of different concentrations of electrolyte (NaCl and Na2SO4), as well as the neutral and alkaline pH media. The electrochemical treatment was conducted in a continuous flow reactor, in which the electrolysis time of the AM 100 ppm was 6 hours. The performance of electrochemical process was evaluated by UV-vis spectrophotometry, chemical oxygen demand (COD) and total organic carbon (TOC). The results showed that with increasing current density, it was possible to obtain 100 % of color removal at Ti/IrO2-Ta2O5 and Ti/Pt electrodes. Regarding the color removal efficiency, increasing the concentration of electrolyte promotes a higher percentage of removal using 0,02 M Na2SO4 and 0,017 M NaCl. Concerning to the aqueous medium, the best color removal results were obtained in alkaline medium using Ti/Pt. In terms of organic matter, 86 % was achieved in neutral pH medium for Ti/Pt; while a 30 % in an alkaline medium. To understand the electrochemical behavior due to the oxygen evolution reaction, polarization curves were registered, determining that the presence of NaCl in the solution favored the production of active chlorine species. The best results in energy consumption and cost were obtained by applying lower current density (20 mA/cm2 ) in 6 hours of electrolysis.

Processos Oxidativos Avançados para Remediação de Águas Contaminadas por Pesticidas

Este trabalho teve como objectivo inicial o estudo de processos oxidativos avançados de forma a remediar e tratar águas contaminadas por pesticidas. No entanto, ao longo do trabalho experimental, constatou-se que os produtos resultantes da degradação de pesticidas são muitas vezes mais tóxicos do que os compostos que lhes deram origem e que, por isso, degradar um composto nem sempre é o melhor para o ambiente. Assim, neste trabalho, procurou-se estudar o processo de degradação com o objectivo de minimizar o impacto ambiental dos pesticidas na água e no ambiente em geral. A parte experimental deste trabalho foi dividida em duas etapas, sendo que, em ambas, a voltametria de onda quadrada e a espectrofotometria de UV/Vis foram os métodos de análise utilizados, para acompanhar o processo de fotodegradação. Na primeira etapa estudou-se a relação entre a estrutura química dos pesticidas MCPA, MCPP, 2.4-D e Dicloroprop e a sua fotodegradação. Soluções aquosas dos pesticidas enunciados foram submetidas a irradiação UV/vis, com incrementos variáveis de tempo de irradiação. Os resultados obtidos, nesta etapa, permitiram constatar diferenças na percentagem de degradação dos diferentes pesticidas. Dos pesticidas estudados verificou-se uma maior fotodegradação para o MCPA e MCPP seguido do Dicloroprop e finalmente o 2.4-D que se degradou menos. Os dados obtidos sugerem que a fotodegradação destes pesticidas está intimamente ligada com a estrutura das moléculas. A presença de um maior número de grupos cloro ligados ao anel aromático nos pesticidas 2,4-D e Dicloroprop faz com que estes sejam mais estáveis e por isso se degradam menos que o MCPA e o MCPP. Por outro lado, o facto de o 2,4-D apresentar um potencial de oxidação mais elevado do que o Dicloroprop, faz com que este seja mais difícil de degradar, o que justifica a diferença entre os dois. Desta forma, foi possível concluir que a estrutura dos pesticidas condiciona o processo de degradação, como esperado. Na segunda etapa, estudou-se a estabilização dos pesticidas MCPA e MCPP após encapsulação, com 2-hidroxipropil-β-ciclodextrina (HP-β-CD), em água desionizada e em água do rio. Para tal, submeteram-se as soluções aquosas dos pesticidas com e sem ciclodextrina, a irradiação UV/vis, também com incrementos variáveis de tempo. No caso do MCPA verificou-se que, tanto para água desionizada como para água do rio, que este herbicida encapsulado se degrada bastante menos do que o MCPA livre. O encapsulamento permitiu reduzir quase para metade a taxa de fotodegradação. Assim, confirmou-se que a HP-β-CD permite estabilizar este pesticida, tornando-o mais resistente à fotodegradação. Desta forma, originam-se menos produtos de degradação, os quais podem ser mais tóxicos, e reduz-se de o impacto ambiental deste herbicida. Verificou-se também que o MCPA livre se degrada mais em água do rio do que em água desionizada, provavelmente devido à matéria orgânica presente nesta água, que promove o processo de degradação. No que respeita ao MCPP também se constatou que este herbicida se degrada menos encapsulado do que livre, em água desionizada e em água do rio. Neste caso, conseguiu-se reduzir pouco a taxa de fotodegradação, mas, ainda assim se verifica uma estabilização deste pesticida através do encapsulamento. No entanto, tornou-se mais evidente a estabilização do MCPP após encapsulação em água do rio, já que apresenta uma taxa de fotodegradação menor. Este facto demonstra que a HP-β-CD permite estabilizar também este pesticida, tornando-o mais resistente à fotodegradação, e reduzindo seu impacto ambiental.

Síntese de compostos multiporfirínicos covalentes

Nesta tese descreve-se a síntese de compostos multiporfirínicos covalentes bem como a avaliação da potencial utilização destes compostos como quimiossensores de iões metálicos e para a construção de estruturas supramoleculares com fulerenos. No capítulo 1 desta tese é feita uma introdução à química, propriedades e aplicações das porfirinas e sistemas multiporfirínicos. Relativamente aos sistemas multiporfirínicos é feita uma revisão bibliográfica acerca das estratégias de síntese e abordagem geral à química supramolecular de sistemas porfirina-fulereno. No capítulo 2 são apresentados os resultados referentes à síntese e caracterização dos vários sistemas multiporfirínicos desenvolvidos neste trabalho. De um modo geral, a síntese desses compostos envolveu reações de substituição aromática nucleofílica. Para esse efeito foi necessário preparar porfirinas de partida contendo grupos nucleofílicos nas posições meso (-C6H4OH e -C6H4NH2). Os sistemas multiporfirínicos foram obtidos por reações entre as porfirinas de partida e hexafluorobenzeno ou 5,10,15,20tetraquis(pentafluorofenil)porfirina. Descreve-se também a síntese de uma díade porfirina-C60 e de uma pentíade contendo quatro unidades de porfirina e uma de C60, envolvendo reações de cicloadição 1,3-dipolar e de substituição aromática nucleofílica. Os estudos efetuados ao nível da aplicação de alguns dos novos sistemas multiporfirínicos sintetizados e de um dos seus precursores, a 5-[4(pentafluorofeniloxi)fenil]-10,15,20-trifenilporfirina, como sensores de iões metálicos encontram-se descritos no capítulo 3. Neste capítulo, a título introdutório, é feita uma breve abordagem aos quimiossensores colorimétricos e de fluorescência, apresentando também alguns exemplos de porfirinas como quimiossensores de iões metálicos já descritos na literatura científica. A caracterização fotofísica dos compostos em estudo também é descrita neste capítulo. Os compostos estudados mostraram capacidade de interagir com vários iões metálicos, verificando-se um aumento da seletividade para o ião Hg2+ com o aumento do número de unidades porfirínicas constituintes dos sistemas multiporfirínicos. Os resultados referentes aos estudos de complexação de alguns dos sistemas multiporfirínicos sintetizados com fulerenos encontram-se descritos no capítulo 4. Neste capítulo descreve-se também a caracterização fotofísica dos compostos em estudo. Os estudos realizados com os sistemas multiporfirínicos mostraram uma fraca interação com os fulerenos C60 e C70. No entanto, os valores das constantes de afinidade obtidos com 1-metil-2-(4piridil)[60]fulero[c]pirrolidina mostraram que os sistemas multiporfirínicos apresentam capacidade para formar complexos com este derivado de C60 por coordenação axial e por interações π-π. No capítulo 5 é discutido o trabalho que envolveu o desenvolvimento de novos métodos na síntese de derivados tetrapirrólicos do tipo pirrolo[3,4-b]porfirinas contendo um grupo NH livre no anel exocíclico. A estratégia de síntese requereu a preparação de uma clorina fundida com um anel pirrolina seguida da redução do anel pirrolina. Deste modo obteve-se uma nova clorina fundida com um anel pirrolidina contendo um grupo NH livre. Esta nova clorina foi usada na preparação de uma díade clorina-porfirina por reação de N-arilação com 5,10,15,20-tetraquis(pentafluorofenil)porfirina. A estrutura cristalina da nova díade foi resolvida por difração de raios-X de cristal único. A estrutura dos compostos sintetizados foi estabelecida recorrendo a diversas técnicas espectroscópicas nomeadamente ressonância magnética nuclear (RMN de 1H, 13C e 19F), espectrometria de massa e espectrofotometria de UVvis. No último capítulo desta tese descrevem-se, pormenorizadamente, todas as experiências efetuadas, incluindo os métodos de síntese, purificação e caracterização estrutural dos diversos compostos sintetizados bem como as medições espectrofotométricas e espectrofluorimétricas.

Desenvolvimento de método empregando DLLME para extração e pré-concentração de ferro em amostras de água com diferentes salinidades

Neste trabalho foi desenvolvido e validado um método analítico para a determinação de Fe total em amostras de água com diferentes salinidades empregando a microextração líquido-líquido dispersiva (DLLME), seguido de determinação espectrofotométrica na região do ultravioleta-visível. Nas extrações por DLLME, o Fe foi complexado com pirrolidina ditiocarbamato de amônio (APDC) e extraído após a injeção de uma mistura composta de 1,2-diclorobenzeno (solvente extrator) e etanol (solvente dispersor). Os fatores que influenciam a eficiência de extração (tipo e volume de solvente extrator e dispersor, concentração de APDC e tempo de extração) e subsequente determinação espectrofotométrica foram otimizados. Após otimização das condições, a curva de calibração foi linear entre 0,02 e 2,0 mg L-1 (r 2 = 0,9998) e os limites de detecção e quantificação do método foram de 6,1 e 18,3 µg L-1 , respectivamente. O fator de pré-concentração foi de 3,3. A exatidão foi avaliada em termos de recuperação, com variação entre 90 e 102% e desvio padrão relativo (RSD) inferiores a 12%. A exatidão do método também foi avaliada utilizando um material de referência certificado (SRM 1643e, Elementos Traço em Água), o qual apresentou concordância de 104% e RSD de 5%. O método foi aplicado para amostras de água com diferentes salinidades, como água mineral, estuarina e de alto mar. Além disso, o método proposto apresentou concordância da ordem de 95%, quando comparado com o método 1,10-fenantrolina para a determinação de Fe total.

Heavy elements in chestnuts

Chestnut fruit (CasChestnuts, Castanea sativa, heavy elements, PIXEtanea sativa Miller) are an important food resource in several countries. Portugal is the third largest European producer, with an average production of 25 thousand tons [1], being mainly produced in the North region of Trás-os-Montes. Earlier studies on chestnuts elemental composition were performed by atomic absorption to detect Ca, Mg, Na, K, Cu, Fe, Mn and Zn or by UV-VIS spectrophotometry to detect P [2-3]. In this work the elemental composition of two cultivars (Longal and Judia) of Castanea sativa Miller were studied by means of PIXE (Proton Induced X-ray Emission), using a broad proton beam at CTN-IST, Lisbon. Element identification (from Si to Pb) and quantification (following the method described in [4]) was done. Preliminary results show different composition according with the cultivar, not only in the major and minor elements (as it is described in the bibliography) but also in the trace elements, which includes the presence of Pb and other heavy elements. These preliminary results are part of a wider project that aims to evaluate chestnut fruits decontamination treatment with high energy electron beam and X-rays technology.

Síntese hidrotérmica assistida por micro-ondas de tiO2, e aplicação em nanocompósito

In recent decades have seen a sharp growth in the study area of nanoscience and nanotechnology and is included in this area, the study of nanocomposites with self-cleaning properties. Since titanium dioxide (TiO2) has high photocatalytic activity and also antimicrobial, self-cleaning surfaces in your application has been explored. In this study a comparison was made between two synthesis routes to obtain TiO2 nanoparticles by hydrothermal method assisted by microwave. And after analysis of XRD and SEM was considered the best material for use in nanocomposites. It was deposited nanocomposite film of poly (dimethyl siloxane) (PDMS) with 0.5, 1, 1.5 and 2% by weight of nanoparticles of titanium dioxide (TiO2) by the spraying method. The nanocomposite was diluted with hexane and the suspension was deposited onto glass substrate, followed by curing in an oven with forced air circulation. The photocatalytic activity of the nanocomposite impregnated with methylene blue was evaluated by UV- vis spectroscopy from the intensity variation of absorption main peak at 660nm with time of exposure to the UV chamber. Changes in the contact angle and microhardness were analyzed before and after UV aging test. The effect of ultraviolet radiation on the chemical structure of the PDMS matrix was evaluated by spectrophotometry Fourier transform infrared (FTIR).The results indicated that the addition of TiO2 nanoparticles in the coating PDMS gave high photocatalytic activity in the decomposition of methylene blue, an important characteristic for the development of self-cleaning coatings

Accelerated ageing methodologies for the evaluation of particulate matter role in the corrosion of outdoor-exposed bronzes

Deterioration phenomena occurring on outdoor cultural heritage have been the subject of several studies, but relatively few works investigated the specific role of Particulate Matter (PM) in the corrosion of metals. This topic is really complex and, besides field exposures, accelerated ageing tests are also necessary to isolate and understand deterioration mechanisms due to PM. For this reason, the development of a methodology that allows to reproduce and analyze the effect of PM on alloys through accelerated ageing in climatic chamber has been started. On quaternary bronze specimens, single salts and a mix of them were deposited via two deposition methods: dry (directly depositing the salt on the surface) and wet (dropping a salt solution and drying it), simulating the initial chemical activation of the salts by RH% variations or by raindrops, respectively. Then, to better mimic the composition of real PM, a mixture containing a soluble salts, a mineral, a black carbon and an organic fraction was formulated and spread on the samples. The samples were placed in a climatic chamber and exposed to cyclic variations of T and RH for three weeks. The ageing cycles were set according to predictions on salt deliquescence/recrystallization through E-AIM model and to the evaluation of regional climatic data. The surface evolution was followed by SEM-EDX, Raman, AT-IR and UV-Vis Spectrophotometry. At the end of the test, mass losses were determined and corroded metals removed by pickling were analyzed by AAS. On the basis of the obtained results, the tested procedures seem to be promising in accelerating and mimicking realistic corrosion phenomena, as under the selected conditions, corrosion products typically found at different exposure time (from days to years) on outdoor bronzes were able to progressively form and evolve. Moreover, the two deposition modes simulating different condition of chemical activation of PM deposits allow to obtain complementary information.

A Highly Improved Method For Sensitive Determination Of Amitriptyline In Pharmaceutical Formulations Using An Unmodified Carbon Nanotube Electrode In The Presence Of Sulfuric Acid.

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

Yellowing And Bleaching Of Grey Hair Caused By Photo And Thermal Degradation.

Yellowing is an undesirable phenomenon that is common in people with white and grey hair. Because white hair has no melanin, the pigment responsible for hair colour, the effects of photodegradation are more visible in this type of hair. The origin of yellowing and its relation to photodegradation processes are not properly established, and many questions remain open in this field. In this work, the photodegradation of grey hair was investigated as a function of the wavelength of incident radiation, and its ultrastructure was determined, always comparing the results obtained for the white and black fibres present in grey hair with the results of white wool. The results presented herein indicate that the photobehaviour of grey hair irradiated with a mercury lamp or with solar radiation is dependent on the wavelength range of the incident radiation and on the initial shade of yellow in the sample. Two types of grey hair were used: (1) blended grey hair (more yellow) and (2) grey hair from a single-donor (less yellow). After exposure to a full-spectrum mercury lamp for 200 h, the blended white hair turned less yellow (the yellow-blue difference, Db(*) becomes negative, Db(*)=-6), whereas the white hair from the single-donor turned slightly yellower (Db(*)=2). In contrast, VIS+IR irradiation resulted in bleaching in both types of hair, whereas a thermal treatment (at 81 °C) caused yellowing of both types of hair, resulting in a Db(*)=3 for blended white hair and Db(*)=9 for single-donor hair. The identity of the yellow chromophores was investigated by UV-Vis spectroscopy. The results obtained with this technique were contradictory, however, and it was not possible to obtain a simple correlation between the sample shade of yellow and the absorption spectra. In addition, the results are discussed in terms of the morphology differences between the pigmented and non-pigmented parts of grey hair, the yellowing and bleaching effects of grey hair, and the occurrence of dark-follow reactions.

Lawsonia Inermis-mediated Synthesis Of Silver Nanoparticles: Activity Against Human Pathogenic Fungi And Bacteria With Special Reference To Formulation Of An Antimicrobial Nanogel.

Lawsonia inermis mediated synthesis of silver nanoparticles (Ag-NPs) and its efficacy against Candida albicans, Microsporum canis, Propioniabacterium acne and Trichophyton mentagrophytes is reported. A two-step mechanism has been proposed for bioreduction and formation of an intermediate complex leading to the synthesis of capped nanoparticles was developed. In addition, antimicrobial gel for M. canis and T. mentagrophytes was also formulated. Ag-NPs were synthesized by challenging the leaft extract of L. inermis with 1 mM AgNO₃. The Ag-NPs were characterized by Ultraviolet-Visible (UV-Vis) spectrophotometer and Fourier transform infrared spectroscopy (FTIR). Transmission electron microscopy (TEM), nanoparticle tracking and analysis sytem (NTA) and zeta potential was measured to detect the size of Ag-NPs. The antimicrobial activity of Ag-NPs was evaluated by disc diffusion method against the test organisms. Thus these Ag-NPs may prove as a better candidate drug due to their biogenic nature. Moreover, Ag-NPs may be an answer to the drug-resistant microorganisms.

Remediation Of 17-α-ethinylestradiol Aqueous Solution By Photocatalysis And Electrochemically-assisted Photocatalysis Using Tio2 And Tio2/wo3 Electrodes Irradiated By A Solar Simulator.

TiO2 and TiO2/WO3 electrodes, irradiated by a solar simulator in configurations for heterogeneous photocatalysis (HP) and electrochemically-assisted HP (EHP), were used to remediate aqueous solutions containing 10 mg L(-1) (34 μmol L(-1)) of 17-α-ethinylestradiol (EE2), active component of most oral contraceptives. The photocatalysts consisted of 4.5 μm thick porous films of TiO2 and TiO2/WO3 (molar ratio W/Ti of 12%) deposited on transparent electrodes from aqueous suspensions of TiO2 particles and WO3 precursors, followed by thermal treatment at 450 (°)C. First, an energy diagram was organized with photoelectrochemical and UV-Vis absorption spectroscopy data and revealed that EE2 could be directly oxidized by the photogenerated holes at the semiconductor surfaces, considering the relative HOMO level for EE2 and the semiconductor valence band edges. Also, for the irradiated hybrid photocatalyst, electrons in TiO2 should be transferred to WO3 conduction band, while holes move toward TiO2 valence band, improving charge separation. The remediated EE2 solutions were analyzed by fluorescence, HPLC and total organic carbon measurements. As expected from the energy diagram, both photocatalysts promoted the EE2 oxidation in HP configuration; after 4 h, the EE2 concentration decayed to 6.2 mg L(-1) (35% of EE2 removal) with irradiated TiO2 while TiO2/WO3 electrode resulted in 45% EE2 removal. A higher performance was achieved in EHP systems, when a Pt wire was introduced as a counter-electrode and the photoelectrodes were biased at +0.7 V; then, the EE2 removal corresponded to 48 and 54% for the TiO2 and TiO2/WO3, respectively. The hybrid TiO2/WO3, when compared to TiO2 electrode, exhibited enhanced sunlight harvesting and improved separation of photogenerated charge carriers, resulting in higher performance for removing this contaminant of emerging concern from aqueous solution.

Esi(+)-ms And Gc-ms Study Of The Hydrolysis Of N-azobenzyl Derivatives Of Chitosan.

New N-p-chloro-, N-p-bromo-, and N-p-nitrophenylazobenzylchitosan derivatives, as well as the corresponding azophenyl and azophenyl-p-sulfonic acids, were synthesized by coupling N-benzylvchitosan with aryl diazonium salts. The synthesized molecules were analyzed by UV-Vis, FT-IR, 1H-NMR and 15N-NMR spectroscopy. The capacity of copper chelation by these materials was studied by AAS. Chitosan and the derivatives were subjected to hydrolysis and the products were analyzed by ESI(+)-MS and GC-MS, confirming the formation of N-benzyl chitosan. Furthermore, the MS results indicate that a nucleophilic aromatic substitution (SnAr) reaction occurs under hydrolysis conditions, yielding chloroaniline from N-p-bromo-, and N-p-nitrophenylazo-benzylchitosan as well as bromoaniline from N-p-chloro-, and N-p-nitrophenylazobenzyl-chitosan.

Síntese e estudo de ortossilicatos de zinco luminescentes com aplicação da técnica sol-gel

Usually, the concepts of the Sol-Gel technique are not applied in experimental chemistry courses. This work presents a feasible experiment for chemistry instruction, which involves the synthesis of luminescent materials - Zn2SiO4, with and without Mn2+ as a dopant - by the Sol-Gel technique. The obtained materials were analyzed by scanning electron microscopy, X-Ray diffraction, IR spectroscopy and luminescence measures by UV-vis spectroscopy. The results allow the students to confirm the luminescent properties of the zinc orthosilicate luminophores as well as the structural features expected from literature data.

Modified silicas covalently bounded to 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III): synthesis, spectroscopic and EPR characterization. Catalytic studies

In this work we have studied cyclooctene epoxidation with PhIO, using a new iron porphyrin, 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrinato iron(III), supported on silica matrices via eletrostatic interaction and / or covalent bonds as catalyst. These catalysts were obtained and immobilized on the solid supports propyltrimethylammonium silica (SiN+); propyltrimethylammonium and propylimidazole silica [SiN+(IPG)] and chloropropylsilica (CPS) via elestrostatic interactions and covalent binding. Characterization of the supported catalysts by UV-Vis spectroscopy and EPR (Electron paramagnetic resonance) indicated the presence of a mixture of FeII and FeIII species in all of the three obtained catalysts. In the case of (Z)-cyclooctene epoxidation by PhIO the yields observed for cis-epoxycyclooctane were satisfactory for the reactions catalyzed by the three materials (ranging from 68% to 85%). Such results indicate that immobilization of metalloporphyrins onto solid supports via groups localized on the ortho positions of their mesophenyl rings can lead to efficient catalysts for epoxidation reactions. The catalyst 1-CPS is less active than 1-SiN and 1-SiN(IPG), this argues in favour of the immobilization of this metalloporphyrin onto solids via electrostatic interactions, which is easier to achieve and results in more active oxidation catalysts. Interestingly, the activity of the supported catalysts remained the same even after three successive recyclings; therefore, they are stable under the oxidizing conditions.

Adsorção do corante azul de metileno em partículas de argilominerais: análise dos tamanhos das partículas

Interactions of cationic dye methylene blue (MB) with clay particles in aqueous suspension have been extensively studied. As already known, the number of natural negative charges on the clay modifies significantly the particle sizes dispersed in water and therefore the nature of the interaction with the dye. This work evaluated with UV-Vis spectroscopy method how the clay particle sizes weighted on the adsorption and rearrangement of the dye molecules in aqueous system. The results obtained from light-scattering measurements confirmed that larger particles are found in suspensions containing the high-charged clays as the visible absorption band related to the MB aggregates (570 nm) on these suspensions prevailed.