Pyroclastic material from the PCCVC eruption (Chile) was modified with iron (III) solutions leading to the formation of ferrihydrite surface deposits. The aim of the chemical treatment was to prepare an adsorbent to r...Pyroclastic material from the PCCVC eruption (Chile) was modified with iron (III) solutions leading to the formation of ferrihydrite surface deposits. The aim of the chemical treatment was to prepare an adsorbent to remove arsenic from water by using low-cost mineral wastes. Physicochemical characterization of original and modified materials was carried out by XRD, BET-N2 adsorption, SEM-EDS microscopy and ICP-AES chemical analysis. The modified ash revealed that the increase of bulk iron content was close to 5% (expressed as Fe2O3) whereas surface values were 20.6% Fe2O3. Surface properties showed an increase of BET specific surface with prevalence of mesopores and an increase of total pore volume attributed to presence of nanoscopic iron phase. Kinetic and equilibrium studies were directed to optimize the operative conditions related to the material adsorptive capacity for removing arsenate species. Hence, the adsorbent dose, contact time, pH, stirring and sedimentation were evaluated in batch process. The optimal adsorption dose was 40 g ·L-1 and the solid-liquid contact time was stirring (1 h) and sedimentation (23 h), enough to ensure an adequate turbidity value valid for a pH range between 3.77 and 8.95. The analysis of the isotherm equilibrium by using the Langmuir linear method showed a R2 = 0.995 value. The performance of the treatment to remove arsenic by using a cost-effective adsorbent prepared from volcanic material is a promising technology to apply in the environmental field.展开更多
Photoluminescent silicon nanoparticles 1-2 nm in size were synthesized by a wet chemical procedure and derivatized with propylamine （NH2SiNP）. Surface NH2 groups were used as linkers for additional poly（ethylene gl...Photoluminescent silicon nanoparticles 1-2 nm in size were synthesized by a wet chemical procedure and derivatized with propylamine （NH2SiNP）. Surface NH2 groups were used as linkers for additional poly（ethylene glycol） （PEG） and folic acid （Fo） attachment （PEG-NHSiNP and Fo-NHSiNP, respectively） to enable efficient targeting of the particles to tumors and inflammatory sites. The particles were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ζ potential, dynamic light scattering, and time-resolved anisotropy. The photophysical properties and photosensitizing capacity of the particles and their interaction with proteins was dependent on the nature of the attached molecules. While PEG attachment did not alter the photophysical behavior of NH2SiNP, the attachment of Fo diminished particle photoluminescence. Particles retained the capacity for 1O2 generation; however, efficient 1O2 quenching by the attached surface groups may be a drawback when using these particles as 1O2photosensitizers. In addition, Fo attachment provided particles with the capacity to generate the superoxide anion radical （O2-）. The particles were able to bind tryptophan residues of bovine serum albumin （BSA） within quenching distances. NH2SiNP and PEG-NHSLNP ground state complexes with BSA showed binding constants of （3.1 ± 0.3） × 10^4 and （1.3 ±0.4） × 10^3 M-1, respectively. The lower value observed for PEG-NHSiNP complexes indicates that surface PEGylation leads to a reduction in protein adsorption, which is required to prevent opsonization. An increase in particle luminescence upon BSA binding was attributed to the hydrophobic environment generated by the protein. NH2SiNP-BSA complexes were also capable of resonance energy transfer.展开更多
The morphology, texture, grain size and other physicochemical characteristics of pyroclastic material from the first phases of the Puyehue-Cordon Caulle volcanic complex (PCCVC) eruption, (Southern Andes, Chile), can ...The morphology, texture, grain size and other physicochemical characteristics of pyroclastic material from the first phases of the Puyehue-Cordon Caulle volcanic complex (PCCVC) eruption, (Southern Andes, Chile), can be associated to the model recently reported for the magma storage and its ascent conditions. The eruption started June 4th 2011, and the studied volcanic material corresponds to that collected in Argentine territory at different distances from the source, between 4 and 12 June 2011. The explosive-effusive volcanic process of the first days occurred with the simultaneous emplacement of lava flows and the venting of pyroclastic material, ejecting two well differentiated types of particles. The more abundant was constituted by rhyolitic and light color pumice fragments, characterized by a typical vesicular texture, easy fragmentation and absence of occluded crystalline phases. Particles found in minor proportion were dark color, different in shape and texture and rich in Fe and Ti. They seemed to be more effective for the interaction with emitted gases in the upper part of the column, for this reason, they appeared partially covered by condensation products. The ascent conditions of the magma affected its rheological behavior through variations in the degassing, viscosity and fragmentation. On the other hand, distance to the source, depositional time, volcanic evolution and environmental conditions are factors that affect the chemical composition of collected ash. So, the SiO2/FeO ratio not only increases with the distance but also with the deposition time and volcanic activity. The work was done with the aid of several techniques such as a laser-sediment analyzer, X-ray diffraction (XRD), chemical analysis (bulk and surface), SEM microscopy and Raman “microprobe” spectroscopy. On the other hand, the physicochemical behavior of the pyroclastic material allows us to suggest eventual applications.展开更多
The last volcanic eruption of the Puyehue-Cordon-Caulle Volcanic Complex in the Andes cordillera of western South America, occurring on 4 June 2011, ejected pyroclastic materials that were accumulated in a wide region...The last volcanic eruption of the Puyehue-Cordon-Caulle Volcanic Complex in the Andes cordillera of western South America, occurring on 4 June 2011, ejected pyroclastic materials that were accumulated in a wide region of the northern Patagonia (Argentina), affecting the environment and health of residents within the area. The aim of this work was to evaluate the practicability of using this waste material as a lowcost carrier for mycopesticide formulations. Beauveria bassiana is a recognized fungal agent for arthropod biologic control. Lengthy storage is critical for the development of mycoinsecticide formulations. Accordingly, the search for adequate materials to improve the shelf life of biocontrol products becomes desirable. First, several analytical techniques were employed to characterize the pyroclast physicochemically;then the viability of the fungal conidia was evaluated after an 18-month storage in the volcanic material. Finally, the pathogenicity of the conidia after that prolonged maintenance in the vehicle was assessed on the beetle Alphitobius diaperinus, an insect pest in poultry houses that causes major economic losses. The results from those bioassays proved auspicious for the eventual utilization of the pyroclast as a bioinsecticide carrier especially since the formulation had proven to be stable for at least 18 months under a wide range of environmental conditions. The constant moisture in a closed environment within a 5°C - 40°C temperature range insures a viable state during storage. The results indicate that what would otherwise be volcanic waste may be utilized as an efficient, abundant, inexpensive, and environmentally innocuous carrier of entomopathogenic fungi.展开更多
The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well a...The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species) were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals from abundant Argentinean deposits, was conducted with the aid of different techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES (Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR). This last technique allowed to detect availability of iron species in oxidic environment with different structural complexity and to determine active sites, accessible for arsenate(V) adsorption. The effect was observed through temperature dependence of the first Fe(III) reduction step (below 570°C) of iron-oxide species. The sequence of reducibility: ferrihydrite > hydrous oxide (goethite) > anhydrous oxide (hematite) > structural iron in clay was in agreement with the availability of iron active sites for the reducing process as well as for the arsenate adsorption. The important role of very high iron content in original samples was also observed. The chemical activation of iron-poor clay by a simple and feasible modification with Fe(III) solutions promoted the deposition of the ferrihydrite active phase with an increase of 2.81% (expressed as Fe2O3) respect to the original content of 1.07%, constituting an accessible and eco-friendly technological alternative to solve the environmental problem of water containing arsenic.展开更多
The dynamic behavior caused by hydro-adsorption process of materials based on a rich mineral clinoptilolite together with their acidic, basic and calcinated forms has been studied by the dynamic laser speckle (DLS) te...The dynamic behavior caused by hydro-adsorption process of materials based on a rich mineral clinoptilolite together with their acidic, basic and calcinated forms has been studied by the dynamic laser speckle (DLS) technique. We propose a modified Peleg’s equation to improve fitting of DLS data. Textural (BET), structural (XRD) and spectroscopic (FTIR) properties were also studied and compared. We demonstrated that DLS was the most sensitive, simple and inexpensive method for comparing the performance of adsorptive materials with slightly modified surfaces. It also allowed the correlation with physicochemical properties.展开更多
The mass spectral fragmentation of thiosemicarbazones synthesized from acetophenones has been studied by CG/MS. These carbonyl compounds exhibit chromatographic peaks which are not observed in aliphatic analogues or t...The mass spectral fragmentation of thiosemicarbazones synthesized from acetophenones has been studied by CG/MS. These carbonyl compounds exhibit chromatographic peaks which are not observed in aliphatic analogues or those synthesized from aldehydes. The analysis of the corresponding spectra has allowed structural assignment to the dimerization of gas phase neutral fragments. Theoretical calculations (DFT level) also provide evidence to support the experimental observations.展开更多
Low-cost adsorbents constituted by Fe-modified-aluminosilicates （laminar and zeolite type minerals） were developed and characterized to be used in the arsenic removal from groundwater. Iron activation was carried o...Low-cost adsorbents constituted by Fe-modified-aluminosilicates （laminar and zeolite type minerals） were developed and characterized to be used in the arsenic removal from groundwater. Iron activation was carried out ＂in situ＂ by the synthesis and deposition of mesoporous ferrihydrite. Natural iron-rich aluminosilicate was used as reference. All samples were characterized by X-ray diffraction, Raman spectroscopy, BET N2-adsorption, SEM-EDS microscopy and ICP chemical analysis. Experimental results of arsenic sorption showed that iron-poor raw materials were not active, unlike iron activated samples. The iron loading in all activated samples was below 5% （expressed as Fe203）, whereas the removal capacity of these samples reaches between 200-700 gg of As by g of adsorbent, after reusing between 17 cycles and 70 cycles up to adsorbent saturation. Differences can be associated to mineral structure and to the surface charge modification by iron deposition, affecting the attraction of the As-oxoanion. On the basis of low-cost raw materials, the easy chemical process for activation shows that these materials are potentially attractive for As（V） removal. Likewise, the activation of clay minerals, with natural high content of iron, seems to be a good strategy to enhance the arsenic adsorption ability and consequently the useful life of the adsorbent.展开更多
文摘Pyroclastic material from the PCCVC eruption (Chile) was modified with iron (III) solutions leading to the formation of ferrihydrite surface deposits. The aim of the chemical treatment was to prepare an adsorbent to remove arsenic from water by using low-cost mineral wastes. Physicochemical characterization of original and modified materials was carried out by XRD, BET-N2 adsorption, SEM-EDS microscopy and ICP-AES chemical analysis. The modified ash revealed that the increase of bulk iron content was close to 5% (expressed as Fe2O3) whereas surface values were 20.6% Fe2O3. Surface properties showed an increase of BET specific surface with prevalence of mesopores and an increase of total pore volume attributed to presence of nanoscopic iron phase. Kinetic and equilibrium studies were directed to optimize the operative conditions related to the material adsorptive capacity for removing arsenate species. Hence, the adsorbent dose, contact time, pH, stirring and sedimentation were evaluated in batch process. The optimal adsorption dose was 40 g ·L-1 and the solid-liquid contact time was stirring (1 h) and sedimentation (23 h), enough to ensure an adequate turbidity value valid for a pH range between 3.77 and 8.95. The analysis of the isotherm equilibrium by using the Langmuir linear method showed a R2 = 0.995 value. The performance of the treatment to remove arsenic by using a cost-effective adsorbent prepared from volcanic material is a promising technology to apply in the environmental field.
文摘Photoluminescent silicon nanoparticles 1-2 nm in size were synthesized by a wet chemical procedure and derivatized with propylamine （NH2SiNP）. Surface NH2 groups were used as linkers for additional poly（ethylene glycol） （PEG） and folic acid （Fo） attachment （PEG-NHSiNP and Fo-NHSiNP, respectively） to enable efficient targeting of the particles to tumors and inflammatory sites. The particles were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ζ potential, dynamic light scattering, and time-resolved anisotropy. The photophysical properties and photosensitizing capacity of the particles and their interaction with proteins was dependent on the nature of the attached molecules. While PEG attachment did not alter the photophysical behavior of NH2SiNP, the attachment of Fo diminished particle photoluminescence. Particles retained the capacity for 1O2 generation; however, efficient 1O2 quenching by the attached surface groups may be a drawback when using these particles as 1O2photosensitizers. In addition, Fo attachment provided particles with the capacity to generate the superoxide anion radical （O2-）. The particles were able to bind tryptophan residues of bovine serum albumin （BSA） within quenching distances. NH2SiNP and PEG-NHSLNP ground state complexes with BSA showed binding constants of （3.1 ± 0.3） × 10^4 and （1.3 ±0.4） × 10^3 M-1, respectively. The lower value observed for PEG-NHSiNP complexes indicates that surface PEGylation leads to a reduction in protein adsorption, which is required to prevent opsonization. An increase in particle luminescence upon BSA binding was attributed to the hydrophobic environment generated by the protein. NH2SiNP-BSA complexes were also capable of resonance energy transfer.
文摘The morphology, texture, grain size and other physicochemical characteristics of pyroclastic material from the first phases of the Puyehue-Cordon Caulle volcanic complex (PCCVC) eruption, (Southern Andes, Chile), can be associated to the model recently reported for the magma storage and its ascent conditions. The eruption started June 4th 2011, and the studied volcanic material corresponds to that collected in Argentine territory at different distances from the source, between 4 and 12 June 2011. The explosive-effusive volcanic process of the first days occurred with the simultaneous emplacement of lava flows and the venting of pyroclastic material, ejecting two well differentiated types of particles. The more abundant was constituted by rhyolitic and light color pumice fragments, characterized by a typical vesicular texture, easy fragmentation and absence of occluded crystalline phases. Particles found in minor proportion were dark color, different in shape and texture and rich in Fe and Ti. They seemed to be more effective for the interaction with emitted gases in the upper part of the column, for this reason, they appeared partially covered by condensation products. The ascent conditions of the magma affected its rheological behavior through variations in the degassing, viscosity and fragmentation. On the other hand, distance to the source, depositional time, volcanic evolution and environmental conditions are factors that affect the chemical composition of collected ash. So, the SiO2/FeO ratio not only increases with the distance but also with the deposition time and volcanic activity. The work was done with the aid of several techniques such as a laser-sediment analyzer, X-ray diffraction (XRD), chemical analysis (bulk and surface), SEM microscopy and Raman “microprobe” spectroscopy. On the other hand, the physicochemical behavior of the pyroclastic material allows us to suggest eventual applications.
文摘The last volcanic eruption of the Puyehue-Cordon-Caulle Volcanic Complex in the Andes cordillera of western South America, occurring on 4 June 2011, ejected pyroclastic materials that were accumulated in a wide region of the northern Patagonia (Argentina), affecting the environment and health of residents within the area. The aim of this work was to evaluate the practicability of using this waste material as a lowcost carrier for mycopesticide formulations. Beauveria bassiana is a recognized fungal agent for arthropod biologic control. Lengthy storage is critical for the development of mycoinsecticide formulations. Accordingly, the search for adequate materials to improve the shelf life of biocontrol products becomes desirable. First, several analytical techniques were employed to characterize the pyroclast physicochemically;then the viability of the fungal conidia was evaluated after an 18-month storage in the volcanic material. Finally, the pathogenicity of the conidia after that prolonged maintenance in the vehicle was assessed on the beetle Alphitobius diaperinus, an insect pest in poultry houses that causes major economic losses. The results from those bioassays proved auspicious for the eventual utilization of the pyroclast as a bioinsecticide carrier especially since the formulation had proven to be stable for at least 18 months under a wide range of environmental conditions. The constant moisture in a closed environment within a 5°C - 40°C temperature range insures a viable state during storage. The results indicate that what would otherwise be volcanic waste may be utilized as an efficient, abundant, inexpensive, and environmentally innocuous carrier of entomopathogenic fungi.
文摘The study reports aspects that allowed to correlate structural and redox properties of iron species deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species) were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals from abundant Argentinean deposits, was conducted with the aid of different techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES (Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR). This last technique allowed to detect availability of iron species in oxidic environment with different structural complexity and to determine active sites, accessible for arsenate(V) adsorption. The effect was observed through temperature dependence of the first Fe(III) reduction step (below 570°C) of iron-oxide species. The sequence of reducibility: ferrihydrite > hydrous oxide (goethite) > anhydrous oxide (hematite) > structural iron in clay was in agreement with the availability of iron active sites for the reducing process as well as for the arsenate adsorption. The important role of very high iron content in original samples was also observed. The chemical activation of iron-poor clay by a simple and feasible modification with Fe(III) solutions promoted the deposition of the ferrihydrite active phase with an increase of 2.81% (expressed as Fe2O3) respect to the original content of 1.07%, constituting an accessible and eco-friendly technological alternative to solve the environmental problem of water containing arsenic.
文摘The dynamic behavior caused by hydro-adsorption process of materials based on a rich mineral clinoptilolite together with their acidic, basic and calcinated forms has been studied by the dynamic laser speckle (DLS) technique. We propose a modified Peleg’s equation to improve fitting of DLS data. Textural (BET), structural (XRD) and spectroscopic (FTIR) properties were also studied and compared. We demonstrated that DLS was the most sensitive, simple and inexpensive method for comparing the performance of adsorptive materials with slightly modified surfaces. It also allowed the correlation with physicochemical properties.
文摘The mass spectral fragmentation of thiosemicarbazones synthesized from acetophenones has been studied by CG/MS. These carbonyl compounds exhibit chromatographic peaks which are not observed in aliphatic analogues or those synthesized from aldehydes. The analysis of the corresponding spectra has allowed structural assignment to the dimerization of gas phase neutral fragments. Theoretical calculations (DFT level) also provide evidence to support the experimental observations.
文摘Low-cost adsorbents constituted by Fe-modified-aluminosilicates （laminar and zeolite type minerals） were developed and characterized to be used in the arsenic removal from groundwater. Iron activation was carried out ＂in situ＂ by the synthesis and deposition of mesoporous ferrihydrite. Natural iron-rich aluminosilicate was used as reference. All samples were characterized by X-ray diffraction, Raman spectroscopy, BET N2-adsorption, SEM-EDS microscopy and ICP chemical analysis. Experimental results of arsenic sorption showed that iron-poor raw materials were not active, unlike iron activated samples. The iron loading in all activated samples was below 5% （expressed as Fe203）, whereas the removal capacity of these samples reaches between 200-700 gg of As by g of adsorbent, after reusing between 17 cycles and 70 cycles up to adsorbent saturation. Differences can be associated to mineral structure and to the surface charge modification by iron deposition, affecting the attraction of the As-oxoanion. On the basis of low-cost raw materials, the easy chemical process for activation shows that these materials are potentially attractive for As（V） removal. Likewise, the activation of clay minerals, with natural high content of iron, seems to be a good strategy to enhance the arsenic adsorption ability and consequently the useful life of the adsorbent.
