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Biocides are compounds that are broadly used to protect products and equipment against microbiological damage. Encapsulation can effectively increase physicochemical stability and allow for controlled release of encapsulated biocides. We categorized microencapsulation into coacervation, sol-gel, and self-assembly methods. The former comprises internal phase separation, interfacial polymerization, and multiple emulsions, and the latter include polymersomes and layer-by-layer techniques. The focus of this review is the description of these categories based on their microencapsulation methods and mechanisms. We discuss the key features and potential applications of each method according to the characteristics of the biocide to be encapsulated, relating the solubility of biocides to the capsule-forming materials, the reactivity between them and the desired release rate. The role of encapsulation in the safety and toxicity of biocide applications is also discussed. Furthermore, future perspectives for biocide applications and encapsulation techniques are presented.
Assuntos
Desinfetantes , Emulsões , Polimerização , SolubilidadeRESUMO
Agroindustrial wastes (rice husk, exhausted bark acacia, and tobacco dust) and foundry sands from the iron foundry industry were employed as a support source for photocatalysts. TiCl4 was used as the titanium precursor in the preparation of the supported photocatalysts. The solids were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), diffuse reflectance spectroscopy over the ultraviolet range (DRS-UV), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), nitrogen adsorption-desorption at -196 °C and zeta potential (ZP) measurements. The systems were evaluated for the photodegradation of rhodamine B (RhB). Among the tested systems, the highest percentage of dye degradation was reached by the catalyst prepared with foundry sand supports, with values of 65% under ultraviolet and 39% under visible radiation, whereas under the same conditions, the catalyst prepared with rice husk showed the best photocatalytic performance among the samples prepared with agroindustrial wastes with values of 43% under ultraviolet and 38% under visible radiation. Strong Spearman's correlations among the photocatalytic activity, the zeta potential (ζp>0.900) and the band gap energy (ζp>0.895) were observed. Exploratory tests with tap water samples revealed that the system may be sensitive to other analytes present in these environmental samples.
Assuntos
Resíduos Industriais , Fotólise , Titânio/química , Poluentes Químicos da Água/química , Purificação da Água , Agricultura , Catálise , Ferro , Luz , Magnoliopsida , Metalurgia , Microscopia Eletrônica de Varredura , Nitrogênio , Rodaminas , Espalhamento a Baixo Ângulo , Espectrometria por Raios X , Difração de Raios XRESUMO
Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the SiOSi bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric SiOSi stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials.
Assuntos
Compostos de Organossilício/química , Dióxido de Silício/química , Modelos Moleculares , Compostos de Organossilício/síntese química , Transição de Fase , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral RamanRESUMO
The impact of drilling oil activities in the Brazilian Bonito Field/Campos Basin (Rio de Janeiro) shell drilling (300 m) using nonaqueous fluids (NAFs) was investigated with respect to Al, Fe, Mn, Ba, Co, Pb, Cu, As, Hg, Cr, Ni, Zn, Cd, V, and aliphatic and polynuclear aromatic hydrocarbons concentrations in the sediment. Sampling took place in three different times during approximately 33 months. For the metals Al, As, Co, Cr, Cu, Cd, Fe, Ni, Mn, V, and Zn, no significant variation was observed after drilling activities in most of the stations. However, an increase was found in Ba concentration--due to the drilling activity--without return to the levels found 22 months after drilling. High Ba contents was already detected prior to well drilling, probably due to drilling activities in other wells nearby. Hydrocarbon contents also suggest previous anthropogenic activities. Aliphatic hydrocarbon contents were in the range usually reported in other drilling sites. The same behavior was observed in the case of polyaromatic hydrocarbons. Nevertheless, the n-alkane concentration increased sharply after drilling, returning almost to predrilling levels 22 months after drilling activities.
Assuntos
Monitoramento Ambiental/métodos , Indústrias Extrativas e de Processamento , Sedimentos Geológicos/análise , Metais/análise , Poluentes da Água/análise , Brasil , Hidrocarbonetos , PetróleoRESUMO
A series of silica-based materials were employed as sorbents within solid-phase microextraction vials. The aim of the study was to evaluate the effect of an additional phase on the distribution of the volatile and less volatile analytes. The adsorption of six probe molecules, namely isoamyl acetate, ethyl hexanoate (ethyl caproate), phenylethyl alcohol, ethyl octanoate (ethyl caprilate), 2-phenylethyl acetate, and ethyl decanoate, was monitored by detecting the desorbed amount on a DVD-CAR-PDMS fiber from Pilsen beer. The microextraction process involved the presence of different silica-based phases produced via different methods: xerogel produced by hydrolytic and non-hydrolytic routes, aerogel, pyrogenic, and precipitated silica. The resulting data are discussed in correlation with sorbent texture properties (specific area and pore diameter). The modification of silica with alkyl groups also affects the preconcentrated amount of the target molecules in the headspace. The presence of sorbents was shown to affect the analyte signal more than the addition of NaCl or the use of ultrasound.
Assuntos
Cerveja/análise , Dióxido de Silício/química , Microextração em Fase Sólida/métodos , Adsorção , Estrutura Molecular , VolatilizaçãoRESUMO
A series of octadecylsilane-modified silicas were prepared by sol-gel and grafting methods. Carbon contents and octadecyl chain conformations were shown to depend on the preparative route. Grafting engenders a low carbon content and a liquid-like chain conformation, while the sol-gel method affords a much higher carbon content and a crystalline conformation. The relationships between the toluene adsorption of the hybrid silicas and their chain conformations, their carbon contents and their textural characteristics are discussed. These sorbents, when used in combination with ultraviolet diffuse reflectance spectroscopy (UV DRS), can be employed as a rapid screening method for detection of aromatic compounds in water and air environmental matrices.
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Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.
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Desorption of lead immobilized into cement and concrete matrices was evaluated in the pH range between 4 and 8 within a period of 2 h to 15 days. Lead-desorbed content in aqueous milieu was monitored by Graphite Furnace Atomic Absorption Spectroscopy, while matrices were directly analyzed by X-ray photoelectronic spectroscopy or Rutherford Backscattering spectrometry. For low pH, higher Pb desorption was observed, about 5-7 times higher than that measured in the case of concrete matrices. The inclusion of polyvinyl alcohol as a matrix modifier was evaluated through a factorial design. Polymer inclusion yielded a reduction in Pb desorption, but its effect cannot be justified in terms of the ability of this polymer to chelate the metal. The resulting modified matrices did not present toxicity to Daphnia magna.