AgI Particles Research Articles

Velocity Map Imaging Photoelectron Spectroscopy of Silver Iodide Aerosol Particles.

The valence band electronic structure of isolated silver iodide nanoparticles (AgI NP) was investigated by vacuum-ultraviolet aerosol photoelectron spectroscopy using the velocity map imaging technique (VUV VMI-PES). The VUV VMI-PES results were obtained for polydisperse aerosol produced by aggregation of hydrocolloid of silver iodide particles 8-15 nm in size. The ionization energy of the AgI particles was found to be 6.0±0.1 eV with respect to the vacuum level. The DFT calculations showed that the main contribution to the density of AgI electronic states in the valence region originates from I 5p orbitals. The dependence of the asymmetry parameter on the electron energy showed that the value of the characteristic energy loss of excited photoelectrons was 2.7 eV, which coincided with the band gap of the nanomaterial.

Critical Size of Silver Iodide Containing Glaciogenic Cloud Seeding Particles

AbstractCloud seeding is considered a practical but unproved method to enhance precipitation or suppress hail, due to insufficient knowledge of ice formation and evolution after seeding clouds with ice nucleating particles. This study investigates the size effects on the immersion freezing of aerosol produced from commercial silver iodide (AgI) containing flares at mixed‐phase cloud temperatures from 243 to 267 K. Flare‐generated aerosol exhibited comparable ice nucleation ability (INA) to pure AgI particles in the size range of 200 and 400 nm. Non‐AgI impurities reduced the INA of flare‐generated particles ≤90 nm, which is lower than pure AgI particles ≤40 nm. The critical mass ice‐active site density of the generated aerosols (critical‐nm) was derived, indicating the minimum mass of AgI particles required for efficient ice nucleation. The new parameterization to predict critical‐nm can serve as a reference to optimize the effectiveness of cloud‐seeding materials for practical use.

In situ synthesis of AgI on the nanosilica surface for potential application as a cloud seeding material.

A series of nanosilica/AgI composites was synthesized by in situ reactions between silver nitrate and ammonium iodide deposited on the nanosilica surface using the gas-phase solvate-stimulated mechanosorption modification (GSSMSM) under both dry and wet conditions. The characterization of the synthesized materials was performed by X-ray diffraction (XRD), SEM/EDX (Scanning Electron Microscopy-Energy Dispersive X-ray), thermogravimetric (TGA) and gas sorption methods. As a result of the mechanosorption modification of nanosilica, the bulk density of the samples synthesized in the dry and wet medium increases from 45 g/l for initial nanosilica to 249 g/l and 296 g/l for the modified samples, respectively. The specific surface area of the composites decreased in compared to the nanosilica precursor. The SEM data showed a denser aggregate structure of the nanocomposites compared to the initial nanosilica. The XRD, SEM/EDX and TEM/EDX data indicated the formation of AgI clusters. The AgI particle size was in the range of 6-45 nm. The ice-forming activity of the AgI-containing samples was examined as well. The sample with a smaller size of silver iodide on the surface exhibited superior ice-forming properties, and considering the quantity of utilized AgI, the prepared samples hold promise for application in this field.

Visible-light-driven photocatalytic degradation of a typical UV filter by a novel composite photocatalyst: DFT calculation, degradation pathway, and toxicity evolution

Benzophenone-1 (BP1), as a typical ultraviolet (UV) filter, has been detected in large quantities in aquatic environments and can pose a threat to human health through bioaccumulation. To efficiently remove BP1 from the water environment, a type-II AgI/Bi2Fe4O9 (AgI/BFO) heterojunction with AgI particles tightly grown on Bi2Fe4O9 nanosheets was fabricated. The resultant AgI/BFO heterojunction extended the light absorption range of AgI and promoted charge transfer, which significantly enhanced the photocatalytic performance in BP1 degradation. As a result, the obtained AgI/BFO heterojunction has a degradation rate constant of 0.159 min−1 for BP1, which was 15.9 times BFO and 4.1 times AgI. Capture experiments proved that superoxide radicals (·O2–) and holes (h+) are the main active species. According to the high-performance liquid chromatography-mass spectrometry (HPLC-MS) results, combined with density functional theory (DFT) calculations C5, C7, and C11 were the main attack sites of active species, proposed ten possible degradation intermediates. These degradation intermediates showed increasingly lower toxicity compared to BP1. This work provides a new idea for the study of photocatalytic technology to degrade BPs pollutants in water.

Direct Z-scheme In2O3/AgI heterojunction with oxygen vacancies for efficient molecular oxygen activation and enhanced photocatalytic degradation of tetracycline

A novel In2O3/AgI heterojunction, which has a hollow tubular structure with AgI particles distributed evenly on the outer and inner surfaces of In2O3 microtubes, was fabricated from annealing of AgI adhered to MIL-68(In). The as-prepared heterojunction exhibited much higher photocatalytic activity towards tetracycline degradation compared to In2O3 and AgI. The presence of InAg-1 (1.0 g/L), which has a In2O3:AgI mole ratio of 2:1, could achieve 98.4% removal of tetracycline (20 mg/L) from the solution phase under visible light illumination in 10 min, and it had excellent reusability and stability. The In2O3/AgI heterojunction also exhibited excellent performance in photocatalytic degradation of tetracycline in different types of water matrices and under natural sunlight illumination, demonstrating its potential in practical application. The superior photocatalytic activity of InAg-1 is attributed to the heterojunction formation and generation of oxygen vacancies (OVs), which improve the separation efficiency of photoinduced e−-h+ pairs. Meanwhile, the built-in electric field (BIEF) formed with e- flowing from AgI to In2O3, which is confirmed by density functional theory calculations, helps the formation of a Z-scheme, instead of type II, heterojunction between In2O3 and AgI. Results of radical trapping experiments and electron spin resonance spectra reveal that 1O2, h+, •O2−, and •OH were the key reactive species involved in the photocatalytic degradation process. These findings indicate that Z-scheme photocatalysts with OVs could efficiently activate molecular oxygen and thus have excellent photocatalytic activity towards degradation of organic pollutants.

Construction of novel 0D/2D AgI/CAU-17 heterojunction with excellent photocatalytic performance by in situ deposition-precipitation

Dye effluent is a serious threat to water ecosystem and human health, so it is urgent to develop high-efficient and stable semiconductor photocatalysts to solve the water pollution problem. A novel AgI/CAU-17 composite with 0D/2D hierarchical heterostructure was first constructed by growing AgI particles on CAU-17 nanorods via a mild deposition-precipitation procedure. The optimal 50% AgI/CAU-17 composite displayed the greatest photodegradation rate of 96.7% for RhB, 81.3% for TC and 50.3% for MO, under the simulated solar-light illumination for 70 min. The corresponding apparent rate constants were 0.04401, 0.02227 and 0.01104 min−1, which were 23.79, 15.25 and 19.73-times higher than those of CAU-17, and 4.94, 1.79 and 6.29-times higher than those of AgI. The improved photodegradation performance could be owing to the following causes: 1) The 0D/2D hierarchical heterostructure endowed AgI/CAU-17 composite with tight interfacial contact, which could supply sufficient channels for the migration of photoinduced carriers; 2) The type II charge migrate pathway facilitated the segregation and migration of photoexcited carriers; 3) The AgI/CAU-17 heterostructures reinforced the light absorption capacity and augmented the specific surface area. In addition, various photocatalytic conditions were researched to imitate the degradation process of RhB in the real aqueous system. The radical capture experiments and EPR test attested that h+ and •O2- played an important part in the photodegradation of RhB. This study illustrated the tremendous application potential of AgI/CAU-17 heterojunctions in water purification and provided a simple and reliable idea for the preparation of Bi-MOFs composite photocatalysts.

In suit grown visible light response Z-scheme AgI/Ag/AgVO3 hybrid nanorods with enhanced photocatalytic activity and stability

AgVO3 and AgI have attracted great interest in environmental remediation. Aiming at enhancing the catalytic activity and stability of AgVO3. Visible light response Z-scheme AgI/Ag/AgVO3 hybrid nanorods were prepared by in situ reduction and ion exchange grown. The results of characterization and experiment showed that obtained hybrid material are primarily composed of AgVO3 nanorods, whose surface were closely attached to AgI and Ag particles. Compared with AgVO3 and Ag/AgVO3, the absorbance of Z-scheme AgI/Ag/AgVO3 hybrid nanorods in the visible light region is dramatically enhanced. The degradation efficiency of sample is five times of that of AgVO3 and four times of that of Ag/AgVO3, respectively. And the degradation efficiency still keep 90% after the fourth repeat experiment. The trapping experiments of active species confirmed that the contribution of the degradation for AO-II is mainly attributed to h+ and ∙O2−. The efficient photocatalytic activity can be explained by Z-type mechanism, which promote effective separation of photogenerated charges. This study provides an idea for the design of efficient visible light photocatalysts.

ОЦЕНКА ПОТЕНЦИАЛЬНОГО УВЕЛИЧЕНИЯ КОЛИЧЕСТВА ОСАДКОВ ПРИ ЗАСЕВЕ ОБЛАКОВ ЛЬДООБРАЗУЮЩИМИ ВЕЩЕСТВАМИ НА ОСНОВЕ МОДЕЛИ WRF

The effects of airborne silver iodide (AgI) glaciogenic cloud seeding on the ice nucleation process and enhancement of orographic precipitation is evaluated using the aerosol-aware Thompson-Eidhammer microphysics scheme. The scheme is coupled to the GOCART aerosol model and implemented into the WRF model. Applying the scheme, which takes into account the aerosols serving as ice nuclei, enables the WRF to explicitly predict the effects of changes in aerosol number concentration on the precipitation formation. The selected seeding project was conducted in March 2015 over the Shirkouh Mountain in the center of Iran. The results show that the increased number of aerosols increased the updraft and downdraft, as well as the clouded volume. Therefore, depending on the relative humidity in the upper levels the airborne cloud-seeding operation is simulated to increase or decrease surface precipitation. Simulation data show that the 24-hour accumulated precipitation increased to 9.52% downwind of where AgI particles were released. However, the simulated seeding outcome for the southern regions is a 4.1% decrease in precipitation.

Sintering Bi2O3–B2O3–ZnO ternary low temperature glass by hydration device to solidify iodine containing silver-coated silica gel

Abstract A new glass solidification process aims at radioactive iodine waste was explored in order to reduce the possible harm to environment. Samples with different iodine content in silver-coated silica gel were pretreated by hydration device at 300 °C and then sintered at relatively low temperatures (500, 550 and 600 °C). XRD results show that AgI is mainly chemically fixed in the glass network with some AgI particles being physically wrapped by the glass. Moreover, as the sintering temperature reached to 550 °C, B element crystallized. SEM-EDS results show that Ag and I elements are enriched, while the other elements are evenly distributed. AFM results showed that the sample surface becomes rougher as the iodine content increases in the silver coated silica gel. The FT-IR results show that the structure of the sintered sample is mainly composed of [BiO3], [BiO6] and [BO3]. This study provides a new sintering method by hydration device for the treatment of radioactive iodine waste.

Decoration of amine functionalized zirconium metal organic framework/silver iodide heterojunction on carbon fiber cloth as a filter- membrane-shaped photocatalyst for degrading antibiotics

The development of recyclable photocatalyst with high adsorption and excellent photocatalytic performance has attracted considerable attention. Herein, we report a three-component photocatalyst by constructing porous amine functionalized zirconium metal organic framework (UiO-66-NH2) and broad photo-responsive AgI on flexible carbon fiber cloth (CFC). UiO-66-NH2 nanoparticles (200–400 nm) were in-situ grown on the surface of CFC (16.5 ± 0.5 μm, 4 × 4 cm2) by a solvothermal route, then AgI particles (50–100 nm) were synthesized on CFC/UiO-66-NH2 via a modified chemical bath deposition method. The obtained CFC/UiO-66-NH2/AgI can effectively adsorb 19.0% levofloxacin (LVFX) or 18.4% ciprofloxacin (CIP) in 60 min in the dark and degrade 84.5% LVFX or 79.6% CIP in 120 min under visible light irradiation. Furthermore, the filter-membrane-shaped CFC/UiO-66-NH2/AgI can be utilized to treat the flowing sewage (CIP, 10 mg/L, ~1 L/h), and the removing efficiency of CIP reached 71.0% after 10 grades. Therefore, this work demonstrates the huge application prospect of recyclable CFC/UiO-66-NH2/AgI with high adsorption and photocatalytic capacity in flowing sewage treatment under visible light illumination.

Researches of ice-forming efficiency of products of sublimation of pyrotechnic compositions consisting of silver iodide agi particles and zinc oxide nanotubes

The article is a continuation of experimental research on the search for new, more effective compositions for active effects on clouds and fogs. The paper also presents the results of studies of the ice-forming efficiency of pyrotechnic compositions based on AgI and zinc oxide nanotubes. The dependence of the specific yield of ice-forming active particles for various zinc contents in the initial composition of AD-1 was revealed.

Evaluation of Orographic Cloud Seeding Using a Bin Microphysics Scheme: Three-Dimensional Simulation of Real Cases

AbstractThe University of Pécs and NCAR Bin (UPNB) microphysical scheme was implemented into the mesoscale Weather Research and Forecast (WRF) Model that was used to study the impact of silver iodide (AgI) seeding on precipitation formation in winter orographic clouds. Four different experimental units were chosen from the Wyoming Weather Modification Pilot Project to simulate the seeding effect. The results of the numerical experiments show the following: (i) Comparisons with the soundings, snow gauges, and microwave radiometer data indicate that the three-dimensional simulations with detailed microphysics reasonably represent both the dynamics and the microphysics of real clouds. (ii) The dispersion of the AgI particles from the simulated ground-based seeding was effective because of turbulent mixing. (iii) In the investigated cases (surface temperature is less than 0°C), surface precipitation and precipitation efficiency show low susceptibility to the concentrations of cloud condensation nuclei and natural ice nucleating particles. (iv) If the available liquid water content promotes the enhancement of the number of snowflakes by diffusional growth, the surface precipitation can be increased by more than 5%. A novel parameter relevant to orographic clouds, horizontally integrated liquid water path (LWP), was evaluated to find the relation between seeding efficiency and liquid water content. The impact of seeding is negligible if the horizontal LWP is less than 0.1 mm and is apparent if the horizontal LWP is larger than 1 mm, as based on the cases investigated in this study.

Enhanced visible-light photocatalytic performances of ZnO through loading AgI and coupling piezo-photocatalysis

AgI nanoparticles decorated with ZnO flower-like composites were successfully synthesized via citric acid-induced hydrothermal reaction and subsequent chemical deposition in the presence of ammonium hydroxide. The effects of AgI-loading content and the piezoelectric effect of ZnO were investigated using different technologies. The crystal structures and optical and photocatalytic properties revealed that the AgI particles were successfully loaded on the flower-like ZnO through the directed diffusion process of charge-induced deposition. Results also showed that the band gap of the AgI/ZnO composite located between those of the ZnO and the AgI, which was consistent with the theoretic simulation. The degradation rate of RhB induced by the AgI/ZnO composites was three times larger than that of AgI, and the heterojunction exhibited high photocatalytic degradation efficiency for MO and TC. Besides, the photodegradation efficiency remained high after six times. Radical scavenger experiments implied that e− and h+ played important roles in the photocatalytic process. The photodegradation time was considerably shortened while maintaining increased degradation efficiency after adding ultrasonic vibration due to the rapid separation of carriers caused by the piezo-photocatalysis coupling effect.

ESTUDIO DE LA COAGULACIÓN DE PARTÍCULAS COLOIDALES DE AgI POR INFLUENCIA DE QUITOSANO CON SULFATO DE ALUMINIO

El objetivo del presente trabajo fue determinar las condiciones óptimas de la coagulación de partículas suspendidas de yoduro de plata de carga negativa por la acción de soluciones de quitosano, sulfato de aluminio, así como la acción mixta de ambos coagulantes. La suspensión de partículas coloidales de AgI se obtuvo mediante la mezcla de soluciones diluidas de KI y AgNO3 en exceso de KI. En todos los experimentos el volumen del sistema coloidal fue de 600 mL y pH= 6. Los parámetros óptimos del proceso de coagulación se determinó a base del método de Test de Jarras. Para la solución de quitosano los parámetros óptimos fueron: concentración 0,01 %, pH=4,5 y un volumen de 25 mL; para el sulfato de aluminio: concentración 30 ppm, pH=4,0 y un volumen 25 mL. En el caso de la acción mixta de ambos coagulantes los parámetros óptimos fueron 5 mL de una solución al 30 ppm de sulfato de aluminio a pH 4,0 y 20 mL de una solución de quitosano al 0,01 % a pH=4,5 . A base de estos parámetros, se estudió la cinética del proceso de coagulación de la suspensión de AgI mediante el método de turbidimetría y se determinó que el proceso de coagulación fue rápido y culminó aproximadamente a los 3 minutos de haber empezado el proceso.

Structure Control for Preparing High-Ionic Conductive Hybrid Nanofiber

Silver iodide (AgI) shows extremely high ionic conductivity, especially in α-phase crystals produced only above 147 °C. To obtain high ionic conductivity of α-AgI crystals near room temperature, we prepared a hybrid nanofiber with nano-sized AgI particles. Initially, potassium iodide (KI) and polyamide 6 (PA6) complex nanofibers were prepared using an iodophor solution of PA6 and KI in formic acid by electrospinning, and immersed into an aqueous silver nitrate solution. Structure and properties of as-spun KI/PA6 complex nanofibers, and the resulting AgI/PA6 hybrid nanofibers, were characterized by scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), and electrical conductivity measurements. Spun complex nanofibers ranged from ∼30 to 300 nm in diameter.

Synthesis of AgI/2D-La2Ti2O7 hybrids as a visible light photocatalyst for degradation of rhodamine B

The AgI/2D-La2Ti2O7 hybrids were obtained via a facile method at room temperature. Rhodamine B, as an organic dye, was used to determine the photocatalytic activity of the samples. The photocatalytic degradation mechanism was also analyzed. Experimental results display that AgI can broaden the light absorption of La2Ti2O7 under the visible light irradiation. The photocatalytic degradation efficiency of the as-synthesized hybrids appears the tendency of first increasing and then decreasing with increasing the usage of La2Ti2O7. When the usage of La2Ti2O7 is 10%, within 60 min, the as-synthesized hybrids possess the maximum of 93.1%. This is higher than 2.1% of La2Ti2O7 and 80.9% of AgI. Moreover, the improved photocatalytic activity can be attributed to AgI particles conjugating with 2D-La2Ti2O7 nanosheets via chemical-bonds, which can enhance the separation and transformation of the photo-generated holes and electrons. In addition, the dominating role is superoxide radicals during the photocatalytic process.

Synthesis of zinc ferrite/silver iodide composite with enhanced photocatalytic antibacterial and pollutant degradation ability

ZnFe2O4/AgI composites were first prepared successfully with a hydrothermal method, and ZnFe2O4 nanoparticles were uniformly decorated on the surface of AgI particles. The photocatalytic activities of the obtained ZnFe2O4/AgI composites were investigated by the degradation of organic pollutants and the inactivation of bacteria under visible light irradiation. The results showed that the introduction of ZnFe2O4 greatly enhanced the light harvesting ability and improved the separation efficiency of the photogenerated charge carriers, which contributed to the enhanced generation of reactive species and thus promoted the photocatalytic performance. The 5% ZnFe2O4/AgI composite exhibited the optimal photocatalytic disinfection of E. coli (100% removal efficiency in 80 min) as well as the photocatalytic degradation of rhodamine B (RhB) (98.5% removal rate in 40 min). Furthermore, four consecutive cycles also demonstrated the stable photocatalytic activity of the as-prepared ZnFe2O4/AgI composites. In addition, H2O2 was identified as the predominant active species in the photocatalytic inactivation of bacteria. This study indicated that ZnFe2O4/AgI composites are a promising candidate for the treatment of wastewater.

Chemical-bond conjugated BiO(OH)xI1-x-AgI heterojunction with high visible light activity and stability in degradation of pollutants

A layered BiO(OH)xI1-x solid solution was grown in situ on the surface of AgI particles by a one-pot co-crystallization method. Based on the results of XPS, EPR, XRD and other techniques, it was verified that a p-n heterojunction was formed through Ag-I-Bi cross-linking bonds in the interface of BiO(OH)xI1-x and AgI due to the common species of I− ions. The resulting BiO(OH)xI1-x-AgI exhibited high efficiency and stability for photodegradation of phenolic compounds with visible light irradiation. No significant AgI decomposition or release of Ag+ or Bi3+ was observed in the photoreaction, and the photoactivity of AgI was enhanced almost 9-fold. These enhanced photocatalytic properties were attributed to the strong interfacial interaction between BiO(OH)xI1-x and AgI by the Ag-I-Bi bond junction. Due to the chemical-bond junction, the photogenerated electrons in the CB of AgI quickly transferred to the CB of BiO(OH)xI1-x to produce O2－, while the holes in the VB of BiO(OH)xI1-x migrated to the VB of AgI to oxidize pollutants in water. The accelerated interfacial charge transfers were responsible for the high photostability and photoactivity of BiO(OH)xI1-x-AgI.

Evaluation of Orographic Cloud Seeding Using a Bin Microphysics Scheme: Two-Dimensional Approach

AbstractA new version of a bin microphysical scheme implemented into the Weather Research and Forecasting (WRF) Model was used to study the effect of glaciogenic seeding on precipitation formation in orographic clouds. The tracking of silver iodide (AgI) particles inside of water drops allows the proper simulation of the immersion nucleation. The ice formations by deposition, condensational freezing, and contact nucleation of AgI particles are also simulated in the scheme. Cloud formation—both stably stratified and convective—and the spread of AgI particles were simulated by idealized flow over a two-dimensional (2D) bell-shaped mountain. The results of numerical experiments show the following: (i) Only the airborne seeding enhances precipitation in stably stratified layer clouds. Seeding can reduce or enhance precipitation in convective clouds. AgI seeding can significantly affect the spatial distribution of the surface precipitation in orographic clouds. (ii) The positive seeding effect is primarily due to additional diffusional growth of AgI-nucleated ice crystals in layer clouds. In convective clouds, seeding-induced changes of both diffusion and riming processes determine the seeding effect. (iii) The seeding effect is inversely related to the natural precipitation efficiency. (iv) Bulk seeding parameterization is adequate to simulate AgI seeding impacts on wintertime orographic clouds. More uncertainties of ground-seeding effects are found between bulk and bin simulations.

WRF Large-eddy Simulations of chemical tracer deposition and seeding effect over complex terrain from ground- and aircraft-based AgI generators

Two ground-based and two airborne cloud seeding events between 2003 and 2005 from a trace chemistry field experiment conducted by the Desert Research Institute (DRI) in the Payette river basin of Idaho are simulated by the Weather Research and Forecasting (WRF) model in Large Eddy Simulation (LES) mode with a grid spacing of 667-m using the recently developed Wintertime silver iodide (AgI) Seeding Parameterization (WASP, Xue et al., 2013a,b). The WASP in WRF was specifically modified to simulate the emissions of both AgI and Indium oxide (In2O3) particles from ground- and aircraft-based generators and the associated interactions with hydrometeors. Validations of model results against available observations from soundings and SNOwpack TELemetry (SNOTEL) data show that WRF simulations reasonably capture the dynamics, the thermodynamics, and the precipitation patterns. The comparisons of deposited Ag and In concentrations between model results and observations, and the analyses of seeding effects and AgI seeding efficiencies show that: The simulated Ag mass concentrations inside the snow are similar to observations ranging mostly from 0 to 10−9kgkg−1 and have high spatial correlations with observations in ground seeding cases (∼ 80%) but lower in airborne seeding (∼ 40%). The simulated Ag/In ratios range between 60 and 600 indicating that ice nucleation of AgI particle dominates the scavenging of AgI in incorporating Ag into the snow. The overall simulated seeding effect of the four cases is 6% increase in precipitation over the LES domain, which is similar to what was inferred from the observations for the entire experiment. The magnitude of the AgI seeding efficiency is one order higher in airborne seeding cases (∼ 1010kgkg−1) compared to ground seeding cases (∼ 109kgkg−1).