Magnetically-extractable hybrid of magnetite, mesoporous silica and titania for the photo-degradation of organic compounds in water

This work addresses the development of a magnetically extractable magnetite-silica-titania photocatalyst to be applied in the degradation of organic compounds in water. MCM-41 silica was successfully deposited on magnetite, providing large surface area for anchoring of TiOx species, and preventing thermally induced conversion of magnetite to hematite. A good correlation between the calculated values and amount of titania deposited on the silica-covered magnetite particles was obtained for a synthesis route involving the treatment of magnetite-silica in boiling ethanolic Ti-precursor solution. Photocatalytic activity in conversion of 4-chlorophenol could only be observed for compositions containing larger than ∼50 wt% titania, whereas increasing the titania content did not significantly improve performance. Experiments carried out at pH ∼ 3.0 and ∼7.2 demonstrated the performance is relatively pH-independent. The structure activity-correlation of the materials is briefly discussed.</p

Síntese e aplicação de sílica mesoporosa modificada com o ligante 4-amino-2-mercaptopirimidina na pré-concentração de Cd (II), Cu(II), Pb(II), Zn(II) e Ni(II) em amostras de águas naturais

Metais constituem um dos poluentes que tem trazido grande preocupação ambiental atualmente, sendo necessário o desenvolvimento de técnicas para remoção destes de efluentes. Para tanto, materiais a base de sílica têm sido desenvolvidos para se realizar a extração em fase sólida deste tipo de poluente, devido a várias potenciais vantagens que estes materiais apresentam, como altas áreas superficiais específicas, estrutura ajustável de partículas e possibilidade de funcinalização. Portanto, o presente trabalho descreve a síntese de sílica mesoporosa utilizando Pluronic P123 como template para formação dos poros e a organofuncionalização do material com o lligante 4-amino-2-mercaptopirimidina, bem como sua posterior aplicação na remoção de Cu(II), Cd(II), Zn(II), Pb(II) e Ni(II) de meios aquosos. A sílica mesoporosa apresentou área superficial específica de 418 m2g1-1, e poros com diâmetro médio de 7,0 nm. Sua funcionalização foi constatada por espectroscopia vibracional em infravermelho, a qual indicou a presença de bandas de CH em 2955 e 2851 cm-1 e de C=C/C=N em 1588, 1512 e 1450 cm-1, após a funcionalização do material. Também foi realizada a análise elementar de N do mesmo, a qual forneceu um ancoramento de 0,1628 mmol de ligante por grama de sílica organofuncionalizada. O experimento cinético demonstrou que o material possui cinética lenta de adsorção para todas as espécies estudadas, e que seu processo adsorção apresenta maior tendência a ser descrita pelo modelo cinético de pesudo-segunda ordem. O pH mais adequado para ocorrência da adsorção dos íons demonstrou-se estar compreendido entre 5 e 6, em decorrência da menor concentração de íons hidrônicos no meio. Sob condições otimizadas de tempo e pH, foram determinadas as capacidades máximas de adsorção para...Among pollutants, metals have become a great environmental problem nowadays, so it is very important to develop techniques to remove them from wastewaters. Silica based materials have been developed to perform the solid-phase extraction of such pollutants, due to many potential advantages these materials present such as high specific superficial area, adjustable particles structure and possibility of functionalization. In view of that, this work describes the synthesis of mesoporous silica using Pluronic P123 as pore template and its organofunctionalization with the ligand 4-amino-2-mercaptopyrimidine as well as its applications for the removal of Cu(II), Zn(II), Pb(II) and Ni(II) from aqueous media. The silica presented specific superficial area of 418m2g-1, and pores with average diameter of 7.0 nm. Its functionalization was verified through infrared vibrational spectroscopy, which indicated the presence of CH bands in 2955 and 2851 cm-1, and also of C=C/C=N bands in 1588, 1512 e 1450 cm-1 after the functionalization of the material. Elemental analysis was carried out, which allowed to calculate the amont of ligand coupled to the surface of the material, providing 0,1628 mmol of ligand per gram of organofuncitonalized silica. The kinetic experiments demonstrated that the material exhibits slow adsorption kinetics for all the studied species, and that its adsorption process can be described by the pseudo-second order Kinetic model. The optimum pH for the occurrence of the ions adsorption was found to be between 5 and 6, because of the lower hydronium concentration in the medium. Under optimized contact time and pH conditions. It was determined the maximum adsorption capacities for each metal species, obtaining 13,0 umol g-1 for Zn(II), 12,3 umol g-1 for Cu(II), 3,45 umol g-1 for Ni(II), 2,42 umol... (Complete abstract click electronic access below

Assessment of the superior photocatalytic properties of Sn2+-containing SnO2 microrods on the photodegradation of methyl orange

Abstract A microporous Sn2+-containing SnO2 material presenting microrod morphology and a surface area of 93.0 m2 g–1 was synthesized via a simple hydrothermal route. Sn2+ ions were detected in the interior of the material (15.8 at.%) after the corrosion of a sample through sputtering. The material’s optical properties have demonstrated the absorption of a considerable fraction of visible light up to wavelengths of 671 nm, due to the presence of Sn2+ states in the material’s band structure. The analysis of the internal crystalline structure of a single microrod was carried out with the aid of a focused ion beam microscope and indicated that the material is mesocrystalline down to nanoscale level. It was proposed that the Sn2+ ions occupy intergranular sites in the highly defective crystalline structure of the material and that Sn2+ states, as well as its relatively large surface area, are responsible for the material’s superior photoactivity. The synthesized material was tested as a photocatalyst to decompose hazardous contaminants in water. The photocatalytic performance of the material was much higher than those of commercial TiO2 and SnO2 materials, decomposing nearly all methyl orange (an azo-dye model) content in water (10 mg L–1) in 6 min under UV irradiation for a photocatalyst dose of 5.33 g L–1. The photodegradation of methyl orange was also verified under visible light

Cassava Root Husks as a Sorbent Material for the Uptake and Pre-concentration of Cadmium(II) from Aqueous Media

Cassava husks were undergone to simple processes to obtain a fine powder whose particle diameter varied from 63 μm to 75 μm. The characterization of the material indicated the presence of the groups alcohol, amine and thiocarbonyl. The material was tested through batch experiments and the effect of the contact time and pH over the adsorption of Cd(II) ions were evaluated. The material presented a rapid kinetic equilibrium, which was reached in less than 1 min, and the highest Cd(II) uptake occurred at pH 5. The optimum conditions obtained were applied to determine the material’s maximum adsorption capacity with the aid of the linearized Langmuir equation (0.140 mmol g^-1). A pre-concentration experiment was also carried out, and provided a pre-concentration factor of 43-fold

Application of mesoporous SBA-15 silica functionalized with 4-amino-2-mercaptopyrimidine for the adsorption of Cu(II), Zn(II), Cd(II), Ni(II), and Pb(II) from water

This work reports the sol-gel synthesis of an SBA-15 silica and its functionalization with 4-amino-2-mercaptopyrimidine to perform adsorption of metal species from aqueous media. The functionalization of the material was confirmed using FTIR and specific surface area measurements. The final material was tested through batch experiments to uncover its adsorptive properties toward the adsorption of Cu(II), Cd(II), Zn(II), Pb(II), and Ni(II). Contact time and pH conditions were investigated, and the material presented slow adsorption kinetics, which was best described by the pseudo- second order model. In addition, at pH 5-6, the adsorption of the metal ions was favored. Under optimized conditions, the material had its maximum adsorption capacities determined for all metal species studied, and the obtained values were 13.0 mu mol g(-1) for Zn(II), 12.3 mu mol g(-1) for Cu(II), 3.45 mu mol g(-1) for Ni(II), 2.45 mu mol g(-1) for Pb(II), and 0.60 mu mol g(-1) for Cd( II). The capacity differences between each metal ion were discussed in terms of their ionic radii and Person's soft/hard acids/bases concept.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Magnetically-extractable hybrid of magnetite, mesoporous silica and titania for the photo-degradation of organic compounds in water

This work addresses the development of a magnetically extractable magnetite-silica-titania photocatalyst to be applied in the degradation of organic compounds in water. MCM-41 silica was successfully deposited on magnetite, providing large surface area for anchoring of TiOx species, and preventing thermally induced conversion of magnetite to hematite. A good correlation between the calculated values and amount of titania deposited on the silica-covered magnetite particles was obtained for a synthesis route involving the treatment of magnetite-silica in boiling ethanolic Ti-precursor solution. Photocatalytic activity in conversion of 4-chlorophenol could only be observed for compositions containing larger than ∼50 wt% titania, whereas increasing the titania content did not significantly improve performance. Experiments carried out at pH ∼ 3.0 and ∼7.2 demonstrated the performance is relatively pH-independent. The structure activity-correlation of the materials is briefly discussed

Characterization of corn (Zea mays) leaf powder and Its adsorption properties regarding Cu(II) and Cd(II) from aqueous samples

In this study, a green adsorbent made of corn leaf powder was applied in the removal of Cu(II) and Cd(II) from water samples. The material was characterized by Fourier transform infrared (FTIR) spectroscopy, which indicated the existence of amine (1375 and 1249 cm(-1)) and carboxylic groups (1730 cm(-1)). Elemental analysis corroborated the results of FTIR, indicating that the substance consisted of 0.63% sulfur and 0.46% nitrogen. The NMR results indicated that thiamine and methionine may be present in the corn leaf substances, which can act in coordination with metal species. Scanning electron microscopy (SEM) indicated the existence of pores of approximately 15 mu m in diameter and a homogeneous particle size. Equilibrium adsorption was attained in 5 min, and the obtained data were applied to a pseudo-second-order kinetic model (r(2) = 0.999 for Cu(II) and Cd(II)). Selective adsorption of Cu(II) was attained at pH 3.0, and the maximum adsorption capacities were attained at pH 6.0. Adsorption isotherms were adjusted to a modified Langmuir equation and the maximum number of moles adsorbed of Cu(II) and Cd(II) were 0.089 and 0.071 mmol g(-1), respectively. The results are superior to many materials currently employed in metal removal from aqueous samples.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Multilayer adsorption of Cu(II) and Cd(II) over Brazilian Orchid Tree (Pata-de-vaca) and its adsorptive properties

Through very simple and inexpensive processes, pata-de-vaca leaves were turned into a powder and applied as an adsorbent for the uptake of Cu(II) and Cd(II) from water. The material was characterized through SEM, EDX, FTIR and surface area measurement. The material had its point of zero charge determined (5.24), and its adsorption capacity was evaluated as a function of time, pH and metal concentration. The material presented fast adsorption kinetics, reaching adsorption equilibrium in less than 5 min and it had a good correlation with the pseudo-second order kinetic model. Optimum pH for the adsorption of Cu(II) and Cd(II) were found to be in the range from 4 to 5, approximately. In the experiment as a function of the analyte concentration, analogously to gas adsorption, the material presented a type II isotherm, indicating the formation of multilayers for both species. Such behavior was explained with basis in the alternation between cations and anions over the material&apos;s surface, and the maximum adsorption capacity, considering the formation of the multilayers were found to be 0.238 mmol L-1 for Cu(II) and 0.113 mmol L-1 for Cd(II).Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Magnetically-extractable hybrid of magnetite, mesoporous silica and titania for the photo-degradation of organic compounds in water

This work addresses the development of a magnetically extractable magnetite-silica-titania photocatalyst to be applied in the degradation of organic compounds in water. MCM-41 silica was successfully deposited on magnetite, providing large surface area for anchoring of TiOx species, and preventing thermally induced conversion of magnetite to hematite. A good correlation between the calculated values and amount of titania deposited on the silica-covered magnetite particles was obtained for a synthesis route involving the treatment of magnetite-silica in boiling ethanolic Ti-precursor solution. Photocatalytic activity in conversion of 4-chlorophenol could only be observed for compositions containing larger than ∼50 wt% titania, whereas increasing the titania content did not significantly improve performance. Experiments carried out at pH ∼ 3.0 and ∼7.2 demonstrated the performance is relatively pH-independent. The structure activity-correlation of the materials is briefly discussed